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Classifications

Harrison's Chapter

ICD-O Morphology

🔗

Mappings

MONDO

MONDO:0020516 thymic neuroendocrine carcinoma

MONDO:0019964 thymic neuroendocrine tumor Not Yet Curated

MONDO:0019964 is the parent thymic neuroendocrine tumor class; this entry is scoped to MONDO:0020516 but draws evidence from series reported under the broader label.

NCIT

NCIT:C171031 Thymus Neuroendocrine Carcinoma

MONDO:0020516 carries NCIT:C171031 as an xref.

ICD-11 Foundation

icd11f:381956131 Carcinoid tumour or other neuroendocrine neoplasms of thymus

Orphanet lists ICD-11 2C27.1 as an exact cross-reference for ORPHA:99869 (thymic neuroendocrine carcinoma); the local ICD-11 Foundation ontology represents this as icd11f:381956131.

NCIT

NCIT:C171031 Thymus Neuroendocrine Carcinoma

MONDO:0020516 carries NCIT:C171031 as an xref.

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Inheritance

1

Sporadic with an autosomal dominant MEN1 subset HP:0000006

Most thymic neuroendocrine carcinoma is sporadic. The heritable fraction is accounted for by autosomal dominant multiple endocrine neoplasia type 1 (germline MEN1), which underlies roughly a quarter to a third of cases.

Autosomal dominant inheritance

Show evidence (2 references)

PMID:40328381 SUPPORT Human Clinical

"multiple endocrine neoplasia type 1 inherited syndrome in 25 patients (34%)"

Quantifies the inherited (MEN1) fraction of an advanced thymic NET cohort.

PMID:20301710 SUPPORT Other

"Each child (regardless of sex) of an individual with MEN1 has a 50% chance of inheriting the pathogenic variant."

GeneReviews gives the autosomal dominant transmission risk that governs cascade testing of relatives. Evidence source is OTHER because GeneReviews is an expert-curated review.

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Subtypes

4

Thymic typical carcinoid (well-differentiated, NET G1) MONDO:0016976

Well-differentiated thymic neuroendocrine neoplasm with organoid architecture, low mitotic count and no necrosis. It is the rarest grade in the thymus - unlike the lung, where typical carcinoid predominates, the vast majority of thymic carcinoids are atypical. Clinically the most indolent grade, but late recurrence still occurs.

Show evidence (1 reference)

PMID:23110006 SUPPORT Human Clinical

"Regarding the tumor classification, our results showed that a vast majority of carcinoids in the thymus correspond to ACs. In addition, our results also indicate that typical carcinoid is a very rare entity."

Surgical series supports typical carcinoid as the rarest grade of thymic neuroendocrine neoplasm, in contrast to the pulmonary distribution.

Thymic atypical carcinoid (moderately differentiated, NET G2/G3) MONDO:0016977

The dominant grade of thymic neuroendocrine neoplasm. Retains carcinoid (organoid) architecture but shows an elevated mitotic count and/or punctate necrosis. In contemporary practice a subset with high proliferation is further separated as "NET G3 highly proliferative atypical carcinoid". Atypical carcinoids present at higher stage than typical carcinoids and account for most ectopic-Cushing and most MEN1-associated thymic disease.

Show evidence (2 references)

PMID:30502716 SUPPORT Human Clinical

"The incidence of Masaoka stage IV was higher (p < 0.0001) in patients with ATC than TC."

Directly supports higher-stage presentation of atypical carcinoid relative to typical carcinoid in a thymic carcinoid series.

PMID:40328381 SUPPORT Human Clinical

"NET G2 atypical carcinoids in 31 patients (48%), 20 patients (31%) with NET G3 highly proliferative atypical carcinoids"

The French national-network series shows atypical carcinoid (G2 plus highly proliferative G3) accounting for about 79% of advanced thymic NET.

Thymic large cell neuroendocrine carcinoma MONDO:0003047

Poorly differentiated, non-small-cell high-grade thymic neuroendocrine carcinoma with a high mitotic rate and almost invariable necrosis. Behaves aggressively; can arise in MEN1 as well as sporadically.

Show evidence (2 references)

PMID:23110006 SUPPORT Human Clinical

"All the patients (3/3) with large cell NEC (3/3) and 16.7% (3/18) of those with AC died of tumor progression."

Supports the markedly worse outcome of thymic large cell neuroendocrine carcinoma relative to atypical carcinoid in the same series.

PMID:35696052 SUPPORT Human Clinical

"One patient had a largely necrotic main tumor with very few mitoses and another nodule with 25 mitoses per 2 mm2, qualifying for the 2021 WHO diagnosis of large cell neuroendocrine carcinoma (LCNEC)."

Documents LCNEC occurring within a MEN1 thymic neuroendocrine tumor cohort.

Small cell carcinoma of the thymus (neuroendocrine type) MONDO:0004122

Poorly differentiated small-cell high-grade thymic neuroendocrine carcinoma with a high mitotic rate and numerous apoptotic bodies. Managed by extrapolation from small cell lung carcinoma with platinum-etoposide chemotherapy; a primary thymic origin must be established by excluding pulmonary or mediastinal-nodal small cell carcinoma.

Show evidence (1 reference)

PMID:29049806 SUPPORT Human Clinical

"The examined tumours were classified as typical carcinoid in 7 patients, atypical carcinoid in 11 patients, large-cell neuroendocrine carcinoma in 3 patients and small-cell carcinoma in 9 patients"

Multicentre surgical series enumerating all four WHO grades of thymic neuroendocrine neoplasm, including small cell carcinoma of the thymus.

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Discussions and Knowledge Gaps

3

What is the actual population incidence of thymic neuroendocrine carcinoma, separated from thymoma and conventional thymic carcinoma and stratified by WHO grade?

KNOWLEDGE GAP OPEN gap_tnec_population_incidence_by_grade

Attached to

pathophysiology#Neuroendocrine Clonal Expansion in the Thymus

Registry analyses report thymic "cancer" incidence per 100,000 but do not break out the neuroendocrine arm, and the largest dedicated series accrue only tens to low hundreds of patients across multi-decade windows. Without a grade-stratified denominator the prevalence block cannot carry a defensible general-population rate, and survival estimates that pool typical carcinoid with high-grade neuroendocrine carcinoma are systematically misleading - the published 5-year figures in this entry range from 53% to 85% largely because of differing grade mixes.

Proposed experiments

Pooled multi-registry grade-stratified incidence analysis

exp_tnec_multiregistry_incidence

Pool SEER with national thymic/NET networks (RYTHMIC, ENDOCAN-RENATEN and equivalents) under central pathology review, reporting age-standardised incidence separately for typical carcinoid, atypical carcinoid, large cell neuroendocrine carcinoma and small cell carcinoma of the thymus.

Decision criterion

Sufficient centrally reviewed cases per grade to estimate incidence with confidence intervals excluding zero.

Would support

A grade-stratified per-100,000 incidence that can populate the general-population prevalence record with numeric bounds.

Does the thymic neuroendocrine cell of origin proposed on immunohistochemical grounds - a normal thymic ACTH/CRH-immunoreactive cell - actually give rise to thymic neuroendocrine carcinoma, and is menin loss in that cell sufficient for transformation?

KNOWLEDGE GAP OPEN gap_tnec_cell_of_origin_and_menin_sufficiency

Attached to

pathophysiology#Menin Tumor Suppressor Loss pathophysiology#Ectopic Corticotropin and CRH Secretion

The cell-of-origin claim currently rests on the observation that non-neoplastic thymus contains scattered ACTH- and CRH-immunoreactive cells and that tumors from Cushing patients stain more strongly for both. That is a correlational immunohistochemical inference, not lineage tracing. No validated mouse model, organoid, patient-derived xenograft or canonical cell line for thymic neuroendocrine carcinoma was identified in the deep-research sweep, so neither the cell of origin nor the sufficiency of menin loss has been tested experimentally.

Proposed experiments

Single-cell and spatial atlas of the putative thymic neuroendocrine precursor

exp_tnec_thymic_ne_precursor_atlas

Profile non-neoplastic human thymus by single-cell and spatial transcriptomics to define the putative neuroendocrine precursor population, and match its signature against thymic neuroendocrine carcinoma tumor transcriptomes.

Would support

A transcriptional lineage relationship between a defined normal thymic neuroendocrine population and the tumor.

Thymic-epithelial-restricted conditional Men1 inactivation

exp_tnec_conditional_men1_mouse

Conditionally inactivate Men1 in a thymic-epithelial-lineage-restricted mouse model to test whether menin loss alone is sufficient to generate thymic neuroendocrine tumors.

Would support

Menin loss as a sufficient initiating lesion in the thymic epithelial lineage.

Would refute

Absence of thymic tumors would indicate that additional cooperating lesions (for example RB-axis loss) are required.

Show evidence (1 reference)

PMID:30502716 PARTIAL Human Clinical

"The thymus contains CRH and ACTH immunoreactive cells that are probably the origin of thymic NET."

The hedged wording ("probably the origin") is itself the evidence that the cell of origin remains an inference rather than an established fact.

Is any systemic therapy for advanced thymic neuroendocrine carcinoma supported by thymus-specific prospective evidence rather than extrapolation from pulmonary and gastroenteropancreatic neuroendocrine neoplasms?

KNOWLEDGE GAP OPEN gap_tnec_systemic_therapy_extrapolation

Attached to

pathophysiology#RB-Axis Tumor Suppressor Loss pathophysiology#Somatostatin Receptor Expression

Every systemic option curated in this entry - platinum-etoposide, everolimus, temozolomide/CAPTEM, somatostatin analogues, PRRT - is recommended by extrapolation. The one prospective study identified (NCT06121271) enrols thymic NET only as one of several unlicensed indications. Because thymic neuroendocrine neoplasms carry a mutational profile distinct from both thymic carcinoma and pulmonary NET (MEN1/MLL2/APC/RB1/TSC2 rather than CDKN2A/TP53), and because they are PD-L1-negative unlike the rest of the thymic epithelial family, the assumption that efficacy transfers is not safe.

Proposed experiments

Registry-embedded prospective systemic-therapy cohorts

exp_tnec_registry_embedded_prospective_cohorts

Basket or registry-embedded prospective cohorts within national thymic/NET networks reporting objective response and progression-free survival separately by WHO grade for platinum-etoposide, everolimus, CAPTEM, somatostatin analogues and PRRT.

Would support

Grade-specific thymus-native efficacy estimates that would replace the current extrapolated recommendations.

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Pathophysiology

10

Menin Tumor Suppressor Loss

Biallelic inactivation of MEN1, which encodes the chromatin-adaptor tumor suppressor menin, is the best-established initiating lesion of thymic neuroendocrine neoplasia. In multiple endocrine neoplasia type 1 a germline loss-of-function MEN1 variant is followed by somatic loss of the remaining allele in the thymic precursor; MEN1 is also the top-ranked somatically altered gene in thymic neuroendocrine neoplasms overall. Roughly a quarter to a third of thymic neuroendocrine neoplasms arise on a MEN1 background, and thymic disease is a disproportionate contributor to MEN1 mortality.

thymic epithelial cell with neuroendocrine differentiation CL:0002293

MEN1 hgnc:7010

thymus UBERON:0002370

Downstream

Neuroendocrine Clonal Expansion in the Thymus Loss of menin-dependent transcriptional restraint permits clonal outgrowth of a thymic epithelial cell with neuroendocrine differentiation.

Show evidence (2 references)

PMID:40068632 SUPPORT Other

"About 25% of the tumors are related to multiple endocrine neoplasia type I (MEN-1), where they contribute significantly to mortality."

Clinical review quantifying the MEN1 fraction of thymic neuroendocrine neoplasms and its mortality impact. Evidence source is OTHER because this is a narrative review.

PMID:37749819 SUPPORT Human Clinical

"those in TNENs were in MEN1, MLL2, APC, RB1"

Targeted panel sequencing of 15 thymic neuroendocrine neoplasms ranks MEN1 as the most frequently altered gene, supporting menin loss as the dominant molecular lesion of this tumor family.

RB-Axis Tumor Suppressor Loss

RB1 is among the top-ranked somatically altered genes in thymic neuroendocrine neoplasms. Loss of the RB axis removes the antiproliferative brake that gates G1/S transit - the conserved hallmark route modeled in the evading_growth_suppressors module. This node is the entry point for the high-grade (large cell neuroendocrine carcinoma and small cell) end of the spectrum, where the classic poorly differentiated neuroendocrine RB1/TP53-loss biology applies.

RB1 hgnc:9884

regulation of cell cycle GO:0051726 ⚠ ABNORMAL

Downstream

Neuroendocrine Clonal Expansion in the Thymus Loss of cell-cycle-checkpoint control permits unrestrained proliferation of the transformed thymic neuroendocrine clone.

Show evidence (2 references)

PMID:37749819 SUPPORT Human Clinical

"those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 ."

Panel sequencing of 15 thymic neuroendocrine neoplasms ranks this gene among the top clinically relevant genomic alterations in the tumor family.

PMID:37749819 SUPPORT Human Clinical

"Further investigation found that the prognosis-related genes were focused on signal pathways of cell cycle control, chromatin remodeling/DNA methylation"

Supports cell-cycle control as one of the pathways in which the prognostically important thymic malignancy lesions concentrate.

Chromatin Regulator Loss

MLL2 (KMT2D), a histone H3K4 methyltransferase, and APC are recurrently altered in thymic neuroendocrine neoplasms, and the prognostically important lesions in thymic malignancy concentrate in chromatin-remodelling/DNA-methylation pathways. This is mechanistically congruent with the chromatin-adaptor function of menin, and is modeled separately from the RB axis because H3K4-methylation and Wnt lesions are not RB/p53-axis tumor-suppressor inactivation.

KMT2D hgnc:7133 APC hgnc:583

chromatin organization GO:0006325 ⚠ ABNORMAL

histone H3K4 methyltransferase activity GO:0042800 ↓ DECREASED

Downstream

Neuroendocrine Clonal Expansion in the Thymus Loss of chromatin-regulatory restraint contributes to the transformed transcriptional program of the expanding neuroendocrine clone.

Show evidence (2 references)

PMID:37749819 SUPPORT Human Clinical

"those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 ."

Panel sequencing of 15 thymic neuroendocrine neoplasms ranks this gene among the top clinically relevant genomic alterations in the tumor family.

PMID:37749819 SUPPORT Human Clinical

"Further investigation found that the prognosis-related genes were focused on signal pathways of cell cycle control, chromatin remodeling/DNA methylation"

Supports chromatin remodelling / DNA methylation as a pathway in which the prognostically important thymic malignancy lesions concentrate.

mTOR Pathway Restraint Loss

TSC2 is among the recurrently altered genes in thymic neuroendocrine neoplasms. TSC2 encodes tuberin, which with hamartin restrains RHEB and hence mTORC1; its loss releases that restraint and drives constitutive TOR signalling. This node - not the RB axis - is the mechanistic rationale for mTOR-inhibitor (everolimus) therapy in this tumor family.

TSC2 hgnc:12363

TOR signaling GO:0031929 ↑ INCREASED

Downstream

Neuroendocrine Clonal Expansion in the Thymus Unrestrained mTORC1 signalling drives the growth and proliferation of the transformed thymic neuroendocrine clone.

Show evidence (1 reference)

PMID:37749819 SUPPORT Human Clinical

"those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 ."

Panel sequencing of 15 thymic neuroendocrine neoplasms ranks this gene among the top clinically relevant genomic alterations in the tumor family.

Neuroendocrine Clonal Expansion in the Thymus

A thymic epithelial cell acquires or retains neuroendocrine differentiation and expands clonally in the prevascular mediastinum. The resulting neoplastic cells are pancytokeratin-positive (confirming epithelial lineage, and distinguishing them from paraganglioma) while co-expressing the neuroendocrine markers chromogranin A and synaptophysin. Proliferative activity - mitotic count and Ki-67 index - grades the lesion and is the marker most consistently associated with outcome, although in the same series overall staining for the wider biomarker panel did not associate with survival or grade.

thymic neuroendocrine tumor cell CL:0000165

neuroendocrine cell differentiation GO:0061101 ⚠ ABNORMAL cell population proliferation GO:0008283 ↑ INCREASED

anterior mediastinum UBERON:0008820

Downstream

Ectopic Corticotropin and CRH Secretion The expanded neuroendocrine clone retains and amplifies the ACTH/CRH secretory program of its thymic cell of origin.

Somatostatin Receptor Expression Neuroendocrine differentiation includes surface somatostatin receptor expression, the substrate for SSTR imaging and SSTR-directed therapy.

Mediastinal Mass Effect and Local Invasion Clonal expansion produces a prevascular mediastinal mass that compresses and invades adjacent thoracic structures.

Nodal and Distant Metastatic Dissemination Proliferating tumor cells disseminate via lymphatics and blood to nodes, bone, lung and pleura.

Thymic neuroendocrine tumor The expanded clone constitutes the defining lesion, a neuroendocrine neoplasm of the thymus.

Show evidence (3 references)

PMID:25294372 SUPPORT Human Clinical

"The thymic neuroendocrine carcinomas (carcinoid tumors) were universally positive for pancytokeratin, but negative for GATA-3 and napsin A. Chromogranin A and synaptophysin were expressed in 92% and 88% of cases, respectively"

Immunohistochemical series of 24 thymic neuroendocrine carcinomas supports an epithelial cell of origin with neuroendocrine marker expression.

PMID:33243039 SUPPORT Human Clinical

"Ki-67 expression ≥1% associated with DoD (P = .003) and death within 5 years (P = .031)."

Supports proliferative activity (Ki-67 index) as associated with death of disease in thymic carcinoid.

PMID:33243039 PARTIAL Human Clinical

"Overall ± staining did not associate with survival or grade."

Boundary condition on the preceding claim: in the same 27-case series the wider immunohistochemical panel, unlike Ki-67 and mitotic count, showed no association with survival or grade.

Ectopic Corticotropin and CRH Secretion

The normal thymus contains scattered ACTH- and CRH-immunoreactive cells, and thymic neuroendocrine tumors are correspondingly immunoreactive for both hormones; tumors from patients with Cushing syndrome stain more strongly for both than those without. Autonomous, non-pituitary secretion of ACTH (with a probable contribution from tumoral CRH) drives bilateral adrenocortical stimulation and ACTH-dependent hypercortisolism. This is the signature functional paraneoplastic syndrome of the thymic neuroendocrine family and frequently brings the tumor to attention before it is otherwise symptomatic.

thymic neuroendocrine tumor cell CL:0000165

corticotropin secretion GO:0051458 ↑ INCREASED peptide hormone secretion GO:0030072 ↑ INCREASED

Downstream

ACTH-Dependent Hypercortisolism Autonomous tumoral ACTH secretion escapes pituitary negative feedback and drives sustained adrenocortical cortisol output.

Show evidence (3 references)

PMID:30502716 SUPPORT Human Clinical

"Ten NET were CRH immunoreactive and 6 were ACTH immunoreactive. Thymic NET with CS exhibited stronger immunoreactivity for ACTH and CRH than those without CS."

Directly links tumoral ACTH and CRH production to the presence of Cushing syndrome in thymic neuroendocrine tumors.

PMID:30502716 SUPPORT Human Clinical

"The thymus contains CRH and ACTH immunoreactive cells that are probably the origin of thymic NET."

Supports a normal thymic ACTH/CRH-immunoreactive cell as the proposed cell of origin, explaining why the ectopic-ACTH syndrome is characteristic of this tumor family.

PMID:37409236 SUPPORT Other

"Ectopic tumoral ACTH secretion has also been observed in MEN1, almost exclusively originating from thymic neuroendocrine tumors."

Review establishing that within MEN1, ectopic ACTH secretion comes almost exclusively from thymic neuroendocrine tumors, underscoring how characteristic this mechanism is of the entity. Evidence source is OTHER because this is a narrative review.

ACTH-Dependent Hypercortisolism

Sustained non-pituitary ACTH stimulation of the adrenal cortex produces ACTH-dependent (secondary) hypercortisolism with the ectopic Cushing syndrome phenotype - hypertension, hypokalaemic metabolic alkalosis, hyperglycaemia, proximal myopathy, osteoporosis and immunosuppression with opportunistic infection. In thymic neuroendocrine tumors this hormonal morbidity is a substantial and sometimes dominant contributor to mortality independent of tumor bulk, and its control is an urgent management priority.

Downstream

Ectopic ACTH-dependent Cushing syndrome Sustained ACTH-driven cortisol excess manifests clinically as ectopic Cushing syndrome.

Hypertension Cortisol excess cross-activates the mineralocorticoid receptor, raising blood pressure.

Hypokalemia Cortisol overwhelms renal 11-beta-HSD2, driving mineralocorticoid-like kaliuresis and hypokalaemic alkalosis.

Show evidence (1 reference)

PMID:40328381 SUPPORT Human Clinical

"11 patients (15%) with ectopic Cushing syndrome"

Quantifies ectopic Cushing syndrome in 15% of a 74-patient advanced thymic NET cohort.

Somatostatin Receptor Expression

A substantial fraction of thymic neuroendocrine neoplasms express membranous somatostatin receptor 2 (SSTR2). SSTR2 expression is the molecular substrate for somatostatin-receptor functional imaging (68Ga-DOTATATE PET) and for SSTR-directed therapy with somatostatin analogues and peptide receptor radionuclide therapy, and expression level tracks with imaging avidity. In advanced thymic NET, somatostatin-receptor imaging is positive in roughly three-quarters of cases.

thymic neuroendocrine tumor cell CL:0000165

somatostatin receptor signaling pathway GO:0038169 ⚠ ABNORMAL

Show evidence (2 references)

PMID:35198446 SUPPORT Human Clinical

"68Ga-DOTATATE PET scans correlated with SSTR2 expression in TET in most patients and appeared to be useful to identify patients with TET who may be amenable to treatment with somatostatin analogues."

Supports SSTR2 expression as the basis of DOTATATE imaging avidity and of somatostatin-analogue treatment selection in thymic epithelial tumors, including atypical carcinoid and small cell carcinoma.

PMID:40328381 SUPPORT Human Clinical

"Positive results for 18F-FDG or somatostain receptor imaging was found in 88% or 74% of cases, respectively."

Quantifies somatostatin-receptor imaging positivity in 74% of advanced thymic NET, supporting SSTR expression as a common tumor feature.

Mediastinal Mass Effect and Local Invasion

The tumor grows as a prevascular (anterior) mediastinal mass and invades mediastinal fat, pleura, pericardium, lung and great vessels, producing chest pain, cough, dyspnoea and occasionally superior vena caval obstruction. Most patients with advanced disease present with locally advanced rather than synchronously metastatic tumor, and completeness of resection is the single strongest modifiable prognostic factor.

anterior mediastinum UBERON:0008820

Downstream

Anterior mediastinal mass The expanding tumor is detected radiologically as a prevascular mediastinal mass.

Chest pain Invasion of pleura, pericardium and chest wall produces chest pain.

Dyspnea Compression or invasion of airway, lung and great vessels causes breathlessness.

Cough Airway irritation and compression by the mediastinal mass produces cough.

Show evidence (2 references)

PMID:40328381 SUPPORT Human Clinical

"A total of 64 patients (87%) had locally advanced Thy-NET and eight (11%) had synchronous metastases, at diagnosis."

Supports locally advanced mediastinal disease as the dominant presentation pattern of advanced thymic NET.

PMID:29049806 SUPPORT Human Clinical

"Overall survival was significantly better in patients who underwent macroscopic complete resection (P = 0.010)."

Supports resectability of the local mediastinal tumor as the key determinant of survival.

Nodal and Distant Metastatic Dissemination

Thymic neuroendocrine carcinoma disseminates to regional mediastinal lymph nodes and then to bone, lung, pleura, liver and brain. Metastasis is frequently metachronous - appearing years after an apparently complete resection - which is why prolonged surveillance is required even for well-differentiated tumors. Pleural spread appears to be almost exclusively metachronous and may reflect perioperative dissemination. In MEN1-associated disease the metachronous-metastasis rate is very high.

Downstream

Mediastinal lymphadenopathy Regional nodal spread presents as mediastinal lymphadenopathy, the commonest metastatic site.

Bone metastasis Haematogenous spread to the skeleton produces bone metastases and bone pain.

Pulmonary metastasis Haematogenous spread seeds the lung, one of the commonest distant sites.

Pleural metastasis Pleural seeding, almost always metachronous, follows local and perioperative dissemination.

Hepatic metastasis Haematogenous spread seeds the liver, a common distant site.

Cerebral metastasis Haematogenous spread seeds the brain, a recognised distant site that alters surveillance imaging and systemic-therapy choice.

Weight loss Advanced metastatic tumor burden produces constitutional weight loss.

Show evidence (3 references)

PMID:40328381 SUPPORT Human Clinical

"Metastatic sites were as follows: lymph nodes (54 patients, 73%), bone (42 patients, 65%), lung (31 patients, 42%), and pleura (31 patients, 42%)."

Enumerates the metastatic site distribution of advanced thymic NET.

PMID:27311764 SUPPORT Human Clinical

"Eighty nine percent of patients developed a metachronous metastasis from the thymic carcinoid."

Supports the predominance of metachronous (late) metastasis in MEN1-associated thymic carcinoid.

PMID:40328381 SUPPORT Human Clinical

"Pleural metastases were almost exclusively metachronous."

Supports the distinctive metachronous timing of pleural spread; the same cohort's discussion raises perioperative dissemination as the suspected explanation.

✶

Histopathology

3

Neuroendocrine architecture with neuroendocrine marker expression OBLIGATE

Diagnosis requires neuroendocrine morphology (organoid nesting, trabeculae, rosettes; or sheets with high-grade cytology) together with immunohistochemical confirmation of neuroendocrine differentiation. Chromogranin A and synaptophysin are positive in the large majority of cases, and pancytokeratin positivity confirms the epithelial lineage that separates thymic neuroendocrine carcinoma from mediastinal paraganglioma.

Show evidence (1 reference)

PMID:25294372 SUPPORT Human Clinical

"Chromogranin A and synaptophysin were expressed in 92% and 88% of cases, respectively, and TTF-1 in 4 (17%) of 24 cases."

Quantifies neuroendocrine marker expression across 24 thymic neuroendocrine carcinomas.

Mitotic count and necrosis grading

Grade is assigned from mitotic count per 2 mm2 and the presence of necrosis - typical carcinoid (low mitotic count, no necrosis), atypical carcinoid (intermediate mitotic count and/or punctate necrosis), and the poorly differentiated large cell neuroendocrine carcinoma and small cell carcinoma (high mitotic count, extensive necrosis). Mitotic count of 4 or more per 2 mm2 and tumor size of 5 cm or more are associated with death of disease.

Show evidence (2 references)

PMID:33243039 SUPPORT Human Clinical

"Mitotic counts ≥4 per 2 mm2 and tumor size ≥5 cm, associated with death of disease (DoD; P = .010 and .016)."

Supports mitotic count and tumor size as histopathologic determinants of outcome in thymic carcinoid.

PMID:35696052 SUPPORT Human Clinical

"another nodule with 25 mitoses per 2 mm2, qualifying for the 2021 WHO diagnosis of large cell neuroendocrine carcinoma (LCNEC)"

Illustrates the mitotic-count threshold that separates high-grade LCNEC from atypical carcinoid under the 2021 WHO scheme.

Absent PD-L1 expression

In contrast to thymoma and thymic squamous cell carcinoma, which typically show a PD-L1-high phenotype, PD-L1 staining was absent in a series of 27 thymic typical and atypical carcinoids. This is a mechanistic argument against reflexive extrapolation of checkpoint-inhibitor strategies from other thymic epithelial tumors to the neuroendocrine arm.

Show evidence (2 references)

PMID:33243039 SUPPORT Human Clinical

"Biomarkers stained tumor cases as follows: PDL-1 = 0%, PAX-5 = 0%, MET = 7.4%"

Directly supports absent PD-L1 staining across 27 mediastinal (thymic) carcinoids.

PMID:34695605 SUPPORT Other

"thymomas and most thymic carcinomas lack currently targetable mutations, have an extraordinarily low tumor mutational burden, but typically have a programmed death-ligand 1high phenotype"

WHO classification overview establishing the PD-L1-high phenotype of thymoma and most thymic carcinomas, the contrast against which the PD-L1-negative neuroendocrine arm stands out. Evidence source is OTHER because this is a classification review.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

15

Cardiovascular 2

Hypertension Hypertension HP:0000822

Show evidence (1 reference)

PMID:35690804 SUPPORT Human Clinical

"Physical examination revealed hypertension (blood pressure: 141/100 mmHg). A mediastinal tumor was discovered to be the cause of the patient's chronic hypokalemia and hypercortisolemia."

Case report of a thymic carcinoid with ectopic ACTH-dependent Cushing syndrome documenting hypertension attributable to the tumor.

Mediastinal lymphadenopathy FREQUENT Mediastinal lymphadenopathy HP:0100721

Show evidence (1 reference)

PMID:40328381 SUPPORT Human Clinical

"Metastatic sites were as follows: lymph nodes (54 patients, 73%)"

Directly supports lymph nodes as the commonest metastatic site (73% of advanced cases), consistent with the FREQUENT band.

Digestive 1

Hepatic metastasis Neoplasm of the liver HP:0002896

HPO has no "hepatic metastasis" class; HP:0002896 Neoplasm of the liver is the closest available parent and does not distinguish a metastatic deposit from a primary hepatic neoplasm. Same NTR-style caveat as the Bone, Pulmonary and Pleural metastasis records.

Show evidence (1 reference)

PMID:23110006 SUPPORT Human Clinical

"Common sites of metastasis included lung, lymph node, brain, lumbar spine, mediastinum, bone, and liver."

Surgical series listing the liver among the common metastatic sites in thymic neuroendocrine tumors.

Metabolism 1

Hypokalemia Hypokalemia HP:0002900

Show evidence (1 reference)

PMID:35690804 SUPPORT Human Clinical

"The presence of hypertension, hypokalemia, and alkalinity suggested Cushing's syndrome, which was proven to be ACTH-dependent ECS by a dexamethasone suppression test."

Documents the hypertension-hypokalaemia-alkalosis triad of ACTH-dependent ectopic Cushing syndrome arising from a thymic neuroendocrine tumor.

Respiratory 2

Dyspnea Dyspnea HP:0002094

Show evidence (1 reference)

PMID:25294372 SUPPORT Human Clinical

"These patients were symptomatic with chest pain, shortness of breath, and dyspnea."

Series of 24 thymic neuroendocrine carcinomas reporting dyspnoea among the presenting symptoms.

Cough Cough HP:0012735

Show evidence (1 reference)

PMID:25294372 PARTIAL Human Clinical

"These patients were symptomatic with chest pain, shortness of breath, and dyspnea."

Establishes the respiratory mass-effect symptom complex in a series of 24 thymic neuroendocrine carcinomas. Marked PARTIAL because the series lists chest pain and breathlessness but not cough specifically.

Constitutional 1

Chest pain Chest pain HP:0100749

Show evidence (1 reference)

PMID:25294372 SUPPORT Human Clinical

"These patients were symptomatic with chest pain, shortness of breath, and dyspnea."

Series of 24 thymic neuroendocrine carcinomas reporting chest pain among the presenting symptoms.

Growth 1

Weight loss Weight loss HP:0001824

Show evidence (1 reference)

PMID:23110006 PARTIAL Human Clinical

"Common sites of metastasis included lung, lymph node, brain, lumbar spine, mediastinum, bone, and liver."

Documents the multi-organ metastatic burden that underlies constitutional weight loss. Marked PARTIAL because the series reports metastatic sites, not weight loss itself; no thymic-NET series quantifies constitutional symptoms.

Neoplasm 1

Pulmonary metastasis FREQUENT Neoplasm of the lung HP:0100526

HPO has no "pulmonary metastasis" class; HP:0100526 Neoplasm of the lung is the closest available parent and does not distinguish a metastatic deposit from a primary lung neoplasm. Same NTR-style caveat as the Bone metastasis and Pleural metastasis records.

Show evidence (2 references)

PMID:40328381 SUPPORT Human Clinical

"lung (31 patients, 42%), and pleura (31 patients, 42%)"

Quantifies pulmonary metastasis in 42% of advanced thymic NET.

PMID:23110006 SUPPORT Human Clinical

"Common sites of metastasis included lung, lymph node, brain, lumbar spine, mediastinum, bone, and liver."

Independent surgical series listing lung among the common metastatic sites.

Other 6

Thymic neuroendocrine tumor OBLIGATE Neoplasm of the thymus HP:0100521

Term choice. HP:0034954 Thymic carcinoid tumor ("A primary thymic neuroendocrine tumor") reads as the obvious match on its label, but under the 2021 WHO scheme "carcinoid" denotes only the well- and moderately-differentiated grades. This entry deliberately spans all four grades including large cell neuroendocrine carcinoma and small cell carcinoma, which are not carcinoids, so HP:0034954 is narrower than the disease it would be annotating. HP:0100521 Neoplasm of the thymus is used instead as the nearest term that covers the whole graded spectrum; the neuroendocrine qualification is carried by preferred_term and by the subtype-level MONDO terms. An HPO NTR for a grade-agnostic "thymic neuroendocrine neoplasm" class would resolve this properly.

Show evidence (2 references)

PMID:40068632 SUPPORT Other

"Thymic carcinoids or neuroendocrine neoplasms (t-NEN) are a rare entity with a dismal prognosis."

Review establishing the entity and its poor prognosis. Evidence source is OTHER because this is a narrative review.

ORPHA:99869 SUPPORT Other

"Thymic neuroendocrine carcinoma is a type of thymic epithelial neoplasm displaying evidence of neuroendocrine differentiation."

Orphanet definition of the entity curated here.

Anterior mediastinal mass OBLIGATE Anterior mediastinal mass HP:0033827

Show evidence (2 references)

ORPHA:99869 SUPPORT Other

"Thymic neuroendocrine carcinoma is a type of thymic epithelial neoplasm displaying evidence of neuroendocrine differentiation."

A thymic epithelial neoplasm is by definition a prevascular (anterior) mediastinal mass, which is why the phenotype is OBLIGATE.

PMID:40328381 PARTIAL Human Clinical

"A total of 64 patients (87%) had locally advanced Thy-NET and eight (11%) had synchronous metastases, at diagnosis."

Characterises the mediastinal primary as usually locally advanced at diagnosis. Marked PARTIAL because it speaks to stage rather than to the presence of the mass.

Ectopic ACTH-dependent Cushing syndrome OCCASIONAL Secondary hypercortisolism HP:0011744

Show evidence (2 references)

PMID:40328381 SUPPORT Human Clinical

"11 patients (15%) with ectopic Cushing syndrome"

Direct quantitative support for the OCCASIONAL (5-29%) frequency band in a 74-patient national-network cohort.

PMID:23110006 SUPPORT Human Clinical

"Three cases of atypical carcinoid (AC) were associated with ectopic Cushing's syndrome."

Independent surgical series documenting ectopic Cushing syndrome in 3 of 21 thymic neuroendocrine tumors (14%), consistent with the OCCASIONAL band.

Bone metastasis FREQUENT Neoplasm of the skeletal system HP:0010622

HPO has no "bone metastasis" class; HP:0010622 Neoplasm of the skeletal system is the closest available parent and is the term other dismech metastasis records use.

Show evidence (1 reference)

PMID:40328381 SUPPORT Human Clinical

"bone (42 patients, 65%)"

Quantifies bone as a metastatic site in 65% of advanced thymic NET, supporting the FREQUENT band within that population.

Pleural metastasis FREQUENT Neoplasm of the respiratory system HP:0100606

HPO has no pleural-neoplasm class; HP:0100606 Neoplasm of the respiratory system is the closest available parent (needs term / NTR candidate: neoplasm of the pleura). The preferred_term carries the intended specificity.

Show evidence (1 reference)

PMID:40328381 SUPPORT Human Clinical

"Pleural metastases were almost exclusively metachronous."

Documents the distinctive metachronous timing of pleural spread in advanced thymic NET.

Cerebral metastasis Brain neoplasm HP:0030692

HP:0030692 Brain neoplasm is defined as "A benign or malignant neoplasm that arises from or metastasizes to the brain", so it does cover metastatic deposits, but it does not distinguish them from a primary brain neoplasm. The preferred_term carries the intended specificity.

Show evidence (1 reference)

PMID:23110006 SUPPORT Human Clinical

"Common sites of metastasis included lung, lymph node, brain, lumbar spine, mediastinum, bone, and liver."

Surgical series listing the brain among the common metastatic sites in thymic neuroendocrine tumors.

🧬

Genetic Associations

5

MEN1 (germline) (Germline loss-of-function variants in MEN1 cause multiple endocrine neoplasia type 1, in which thymic neuroendocrine tumors are an uncommon but disproportionately lethal manifestation. Thymic carcinoids occur in 1-5% of MEN1 patients; conversely a quarter to a third of thymic neuroendocrine neoplasms arise on a MEN1 background.)

Gene: MEN1 hgnc:7010 relationship_type: CAUSATIVE variant_origin: GERMLINE

MEN1 autosomal dominant predisposition

Show evidence (3 references)

PMID:27311764 SUPPORT Human Clinical

"Thymic carcinoids are rare neuroendocrine tumors that occur in 1-5 % of patients with multiple endocrine neoplasia type 1 (MEN1) and are a major cause of morbidity and mortality."

Establishes the MEN1-thymic carcinoid association and its mortality impact.

PMID:27311764 SUPPORT Human Clinical

"Five patients had MEN1 genetic testing, and the genotypes of affected individuals were p.W341X, c.275_286delGCTTCACCGCCC, p.R98X, c.1350+(1_11)del11, and partial duplication of exons 9 and 10."

Documents the germline MEN1 variant spectrum in patients with thymic carcinoid, spanning nonsense, frameshift, splice and copy-number variants.

PMID:20301710 SUPPORT Other

"The molecular diagnosis can be established by identification of a heterozygous pathogenic variant in MEN1 on molecular genetic testing."

GeneReviews establishes germline MEN1 testing as the molecular basis of MEN1 diagnosis, the predisposition context for thymic neuroendocrine tumors. Evidence source is OTHER because GeneReviews is an expert-curated review.

MEN1 (somatic) (MEN1 is also the most frequently somatically altered gene in thymic neuroendocrine neoplasms in tumor panel sequencing, including in patients without a clinical MEN1 syndrome.)

Gene: MEN1 hgnc:7010 relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC

Show evidence (1 reference)

PMID:37749819 SUPPORT Human Clinical

"those in TNENs were in MEN1, MLL2, APC, RB1"

324-gene panel sequencing of 15 thymic neuroendocrine neoplasms ranks MEN1 first among clinically relevant genomic alterations.

RB1 (RB1 is among the top-ranked somatically altered genes in thymic neuroendocrine neoplasms, consistent with RB-axis checkpoint loss as a driver of the higher-grade end of the spectrum.)

Gene: RB1 hgnc:9884 relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC

Show evidence (1 reference)

PMID:37749819 SUPPORT Human Clinical

"those in TNENs were in MEN1, MLL2, APC, RB1"

Ranks RB1 among the most frequently altered genes in thymic neuroendocrine neoplasms.

KMT2D (MLL2 (KMT2D), a histone H3K4 methyltransferase, is recurrently altered in thymic neuroendocrine neoplasms - a chromatin-remodelling lesion that is mechanistically congruent with the chromatin-adaptor function of menin.)

Gene: KMT2D hgnc:7133 relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC

Show evidence (1 reference)

PMID:37749819 SUPPORT Human Clinical

"those in TNENs were in MEN1, MLL2, APC, RB1"

Ranks MLL2 (KMT2D) among the most frequently altered genes in thymic neuroendocrine neoplasms.

ERBB2 (Somatic ERBB2 mutation was associated with shortened disease-free and overall survival specifically in thymic neuroendocrine neoplasm patients, marking it as a candidate prognostic (and potentially actionable) alteration.)

Gene: ERBB2 hgnc:3430 relationship_type: BIOMARKER variant_origin: SOMATIC

Show evidence (1 reference)

PMID:37749819 SUPPORT Human Clinical

"mutation of ERBB2 indicated shortened disease-free survival (DFS) and overall survival (OS) in TNEN patients"

Directly supports ERBB2 mutation as an adverse prognostic marker in thymic neuroendocrine neoplasms.

💊

Medical Actions

10

Complete surgical resection (thymectomy)

Category: Therapeutic Action: Thymectomy NCIT:C29894

Macroscopically complete en-bloc resection of the thymus and tumor, with resection of involved adjacent structures and systematic mediastinal lymph node dissection, is the mainstay of treatment and the only potentially curative modality. Complete resection is associated with significantly better overall survival.

Mechanism Target:

INHIBITS Mediastinal Mass Effect and Local Invasion — En-bloc resection removes the primary tumor and its locally invasive front, the only intervention that can interrupt the pathograph at its anatomical source.

Show evidence (2 references)

PMID:29049806 SUPPORT Human Clinical

"Overall survival was significantly better in patients who underwent macroscopic complete resection (P = 0.010)."

Multicentre surgical series supporting complete resection as the key determinant of survival.

PMID:40068632 SUPPORT Other

"The mainstay of therapy is surgical resection as it is associated with significantly improved long-term survival."

Review confirming surgery as the mainstay of therapy. Evidence source is OTHER because this is a narrative review.

Adjuvant radiotherapy after resection

Category: Therapeutic Action: Radiation Therapy NCIT:C15313

Postoperative radiotherapy is used selectively for incomplete margins or locally advanced disease. The evidence is mixed and weak - in a multicentre surgical series receipt of adjuvant therapy was associated with better relapse-free survival, but a SEER analysis of 160 patients found no survival benefit for radiation delivered as part of primary therapy. Both sides of the evidence are curated here so the uncertainty is explicit.

Show evidence (2 references)

PMID:29049806 PARTIAL Human Clinical

"As for relapse-free survival patients, TNM Stage I or II (P = 0.011) and received adjuvant therapy patients (P = 0.042) showed good survival rates."

Supports a relapse-free survival association with adjuvant therapy. Marked PARTIAL because this is an unadjusted association in a small retrospective series and covers adjuvant therapy generally rather than radiotherapy specifically.

PMID:20485130 REFUTE Human Clinical

"We did not observe any survival benefit for radiation delivered as a part of primary therapy."

SEER analysis finding no survival benefit for primary radiotherapy, the counterweight to the single-series adjuvant association above.

Platinum-etoposide chemotherapy

Category: Therapeutic Action: Chemotherapy NCIT:C15632

Agent: cisplatin CHEBI:27899 carboplatin CHEBI:31355 etoposide CHEBI:4911

For poorly differentiated (small cell and large cell) thymic neuroendocrine carcinoma, platinum plus etoposide is the preferred systemic regimen, adopted by extrapolation from pulmonary and extrapulmonary high-grade neuroendocrine carcinoma. In the French advanced-disease cohort, partial responses were seen most often with cytotoxic chemotherapy. No thymus-specific randomised comparison exists.

Mechanism Target:

INHIBITS Neuroendocrine Clonal Expansion in the Thymus — Platinum DNA crosslinking plus topoisomerase II poisoning kills the rapidly cycling high-grade neuroendocrine clone, which is why response is best in the most proliferative (small cell and large cell) grades.

Show evidence (2 references)

PMID:40068632 SUPPORT Other

"for non-resectable and recurring disease, platinum-based chemotherapies are preferred in neuroendocrine carcinoma, while everolimus and temozolomide are recommended in thymic neuroendocrine tumors."

Review recommending platinum-based chemotherapy for the neuroendocrine carcinoma (high-grade) arm. Evidence source is OTHER because this is a narrative review.

PMID:40328381 SUPPORT Human Clinical

"Partial responses were more frequently observed in patients treated with cytotoxic chemotherapy."

National-network cohort reporting cytotoxic chemotherapy as the modality most often producing partial responses in advanced thymic NET.

Everolimus

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: everolimus CHEBI:68478

The mTOR inhibitor everolimus is recommended for well-differentiated thymic neuroendocrine tumors (as opposed to high-grade neuroendocrine carcinoma), by extrapolation from randomised evidence in lung and gastroenteropancreatic NET. The recurrent TSC2 alterations found in thymic neuroendocrine neoplasms provide a mechanistic rationale for mTOR-pathway targeting in this tumor family.

Mechanism Target:

INHIBITS mTOR Pathway Restraint Loss — Everolimus inhibits mTORC1, restoring the growth-signalling restraint lost when TSC2 (tuberin) is inactivated.

Show evidence (1 reference)

PMID:40068632 SUPPORT Other

"everolimus and temozolomide are recommended in thymic neuroendocrine tumors."

Review recommending everolimus for the well-differentiated arm. Evidence source is OTHER because this is a narrative review and no thymus-specific randomised trial exists.

Temozolomide-based chemotherapy

Category: Therapeutic Action: Chemotherapy NCIT:C15632

Agent: temozolomide CHEBI:72564 capecitabine CHEBI:31348

Temozolomide, usually combined with capecitabine (CAPTEM), is recommended for advanced well-differentiated thymic neuroendocrine tumors. As with everolimus, the recommendation rests on extrapolation from lung and gastroenteropancreatic NET plus published case series; there is no randomised thymus-specific evidence.

Show evidence (1 reference)

PMID:40068632 SUPPORT Other

"everolimus and temozolomide are recommended in thymic neuroendocrine tumors."

Review recommending temozolomide for the well-differentiated arm. Evidence source is OTHER because this is a narrative review.

Somatostatin analogue therapy

Category: Therapeutic Action: Pharmacotherapy NCIT:C15986

Agent: octreotide CHEBI:7726 lanreotide CHEBI:135901

Long-acting somatostatin analogues (octreotide LAR, lanreotide) are used in SSTR2-expressing, DOTATATE-avid thymic neuroendocrine tumors both to control hormone hypersecretion and for antiproliferative effect. Patient selection is driven by SSTR2 immunohistochemistry and somatostatin-receptor PET, which correlate well with one another in thymic epithelial tumors.

Mechanism Target:

ACTIVATES Somatostatin Receptor Expression — Octreotide and lanreotide are SSTR2 agonists: they engage the receptor the tumor expresses, suppressing hormone secretion and exerting an antiproliferative effect.

INHIBITS Ectopic Corticotropin and CRH Secretion — SSTR2 agonism suppresses the autonomous peptide-hormone secretion driving the paraneoplastic syndrome.

Show evidence (1 reference)

PMID:35198446 SUPPORT Human Clinical

"68Ga-DOTATATE PET scans correlated with SSTR2 expression in TET in most patients and appeared to be useful to identify patients with TET who may be amenable to treatment with somatostatin analogues."

Supports SSTR2/DOTATATE-guided selection of thymic epithelial tumor patients for somatostatin-analogue therapy.

Peptide receptor radionuclide therapy (177Lu-DOTATATE)

Category: Therapeutic Action: Peptide Receptor Radionuclide Therapy NCIT:C162449

Agent: lutetium Lu 177 dotatate NCIT:C95020

177Lu-DOTATATE delivers targeted beta radiation to somatostatin-receptor expressing tumor cells and is a rational option for progressive, strongly SSTR-positive thymic neuroendocrine tumors. Thymic NET is an unlicensed indication for Lutathera and is being studied prospectively; use outside a trial is off-label and driven by receptor imaging.

Mechanism Target:

INHIBITS Somatostatin Receptor Expression — 177Lu-DOTATATE exploits tumoral SSTR2 as a delivery route, internalising a beta-emitter that kills the receptor-expressing cell. Receptor expression is both the eligibility criterion and the mechanism.

Show evidence (1 reference)

clinicaltrials:NCT06121271 SUPPORT Human Clinical

"The primary objective of this study is to prospectively evaluate the safety and efficacy in participants treated with Lu-177 DOTATATE (Lutathera) in unresectable or metastatic, somatostatin receptor-expressing neuroendocrine tumours (NET) in currently unlicensed indications (eg, bronchial and thymic NET"

Registered phase 2 trial establishing thymic NET as a target indication for 177Lu-DOTATATE PRRT and confirming its currently unlicensed status.

Control of hypercortisolism

Category: Therapeutic Action: Supportive Care NCIT:C15747

In the functional (ectopic-ACTH) subset, urgent control of hypercortisolism is a management priority independent of tumor-directed therapy, because severe hypercortisolism causes hypokalaemia, hyperglycaemia, thromboembolism and life-threatening opportunistic infection. Options include steroidogenesis inhibitors, glucocorticoid-receptor blockade and, where the tumor is not controllable, bilateral adrenalectomy. Resection of the thymic primary resolves the syndrome when the tumor is resectable.

Mechanism Target:

INHIBITS ACTH-Dependent Hypercortisolism — Steroidogenesis inhibition, glucocorticoid-receptor blockade or bilateral adrenalectomy interrupts the cortisol arm downstream of tumoral ACTH, and resection of the primary removes the ACTH source itself.

Show evidence (2 references)

PMID:30502716 PARTIAL Human Clinical

"Four (36.4%) of the 11 patients had CS."

Establishes the frequency of the Cushing syndrome that this supportive management addresses. Marked PARTIAL because the source characterises the syndrome rather than evaluating its treatment.

PMID:35690804 SUPPORT Human Clinical

"following surgery, her blood pressure returned to normal, and the hypernatremia/hypopotassemia resolved"

Documents resolution of the hypercortisolism-driven hypertension and hypokalaemia after resection of the thymic neuroendocrine primary, supporting tumor removal as the definitive control of the hormonal syndrome.

Genetic counseling and MEN1 surveillance

Category: Counseling / Informational Action: Genetic Counseling NCIT:C15240

A new diagnosis warrants genetic counseling and germline MEN1 testing, with cascade testing of at-risk relatives when a pathogenic variant is found. Confirmed MEN1 carriers enter syndrome-directed surveillance including periodic thoracic imaging, since thymic tumors in MEN1 are aggressive and systematic screening improves prognosis.

Show evidence (2 references)

PMID:35696052 SUPPORT Human Clinical

"TNET in MEN1 patients is an aggressive disease. The prognosis can be better by systematic screening."

Supports systematic surveillance of MEN1 patients for thymic neuroendocrine tumor.

PMID:20301710 SUPPORT Other

"consider chest CT, MRI, or somatostatin receptor scintigraphy octreotide scan annually from age 15 years"

GeneReviews gives the concrete thoracic surveillance modality and schedule for MEN1 carriers, the operational content of this recommendation. Evidence source is OTHER because GeneReviews is an expert-curated review.

Prophylactic transcervical thymectomy in MEN1

Category: Therapeutic Action: Thymectomy NCIT:C29894

Routine transcervical thymectomy performed at the time of parathyroidectomy has been proposed as prophylaxis against thymic carcinoid in MEN1. It is plausible and low-cost when the neck is already open, but the supporting evidence consists only of observational studies and case reports and does not establish that the procedure prevents thymic carcinoid - transcervical thymectomy often leaves residual mediastinal thymic tissue. Curated as a syndrome-specific expert strategy, not proven prevention.

Show evidence (2 references)

clinicaltrials:NCT05061784 PARTIAL Human Clinical

"A case series was built after review of available literature by searching four databases (PubMed, Embase, Medline and Cochrane Library) for observational studies or case reports on routine prophylactic TCT for MEN-1 and the development of thymic carcinoids."

Documents that the evidence base for prophylactic transcervical thymectomy consists of observational studies and case reports. Marked PARTIAL because the registry record establishes the study design rather than an efficacy result.

PMID:20301710 SUPPORT Other

"Thymectomy may prevent thymic carcinoid in males, particularly in smokers."

GeneReviews states the preventive rationale and its risk-group targeting (male sex, smoking) for thymectomy in MEN1. Evidence source is OTHER because GeneReviews is an expert-curated review, and the wording ("may prevent") is itself the measure of how provisional the recommendation is.

🌍

Environmental Factors

1

Tobacco smoking

Smoking is the only environmental exposure with an asserted link to carcinoid risk in the MEN1 setting, and it is the stated basis for targeting prophylactic thymectomy at male smokers. The association is not firmly quantified for thymic neuroendocrine carcinoma specifically, and it is contested: a referral-centre MEN1 thymic-carcinoid series found that two thirds of its patients were non-smokers. It is therefore curated as a probable but unsettled risk factor, and it is a plausible partial confounder of the male predominance recorded in the epidemiology section rather than a proven one.

Show evidence (3 references)

PMID:20301710 SUPPORT Other

"Smoking increases the risk of carcinoid tumors."

GeneReviews Agents/Circumstances to Avoid guidance for MEN1 names smoking as a carcinoid risk factor. Evidence source is OTHER because GeneReviews is an expert-curated review.

PMID:27311764 PARTIAL Human Clinical

"The few published reports associate these tumors with male sex and smoking."

Records the historical male-sex-and-smoking association. Marked PARTIAL because the same paper immediately qualifies it (see the refuting item below).

PMID:27311764 REFUTE Human Clinical

"Six patients were non-smokers (67 %)."

In a 9-patient MEN1 thymic-carcinoid series two thirds of patients were non-smokers, arguing against smoking as a necessary or dominant risk factor and against using smoking status to gate surveillance.

🔬

Biochemical Markers

6

Chromogranin A expression (present)

Show evidence (1 reference)

PMID:25294372 SUPPORT Human Clinical

"Chromogranin A and synaptophysin were expressed in 92% and 88% of cases, respectively"

Quantifies chromogranin A positivity in 92% of thymic neuroendocrine carcinomas.

Synaptophysin expression (present)

Show evidence (1 reference)

PMID:25294372 SUPPORT Human Clinical

"Chromogranin A and synaptophysin were expressed in 92% and 88% of cases, respectively"

Quantifies synaptophysin positivity in 88% of thymic neuroendocrine carcinomas.

Ki-67 proliferation index (present)

Show evidence (1 reference)

PMID:33243039 SUPPORT Human Clinical

"Ki-67 expression ≥1% associated with DoD (P = .003) and death within 5 years (P = .031)."

Supports Ki-67 labeling index as a prognostic biomarker in thymic carcinoid.

Plasma adrenocorticotropic hormone (elevated)

Context: Ectopic Cushing syndrome subset

Show evidence (2 references)

PMID:30502716 PARTIAL Human Clinical

"Thymic NET with CS exhibited stronger immunoreactivity for ACTH and CRH than those without CS."

Supports tumoral ACTH production as the source of the ACTH-dependent syndrome. Marked PARTIAL because the study measures tumor immunoreactivity rather than plasma ACTH concentration.

PMID:35690804 SUPPORT Human Clinical

"The levels of the hormones ACTH, aldosterone, and renin were determined to be 281 pg/mL, 3.0 ng/dL, and 2.1 pg/mL, respectively."

Reports the markedly elevated plasma ACTH concentration in a patient with a thymic carcinoid causing ectopic ACTH-dependent Cushing syndrome.

Serum cortisol (elevated)

Context: Ectopic Cushing syndrome subset

Show evidence (2 references)

PMID:40328381 PARTIAL Human Clinical

"11 patients (15%) with ectopic Cushing syndrome"

Establishes the clinical hypercortisolism syndrome in 15% of advanced thymic NET. Marked PARTIAL because the cohort reports the syndrome rather than cortisol concentrations.

PMID:35690804 SUPPORT Human Clinical

"Cortisol levels increased in the morning, reaching 47.7 ug/dL."

Reports the elevated morning serum cortisol in a thymic carcinoid causing ectopic ACTH-dependent Cushing syndrome.

Somatostatin receptor 2 expression (variable)

Show evidence (1 reference)

PMID:35198446 SUPPORT Human Clinical

"SSTR2 expression was identified in 29 (of 80, 36.3%) TET including 2/2 (100%) small cell carcinomas, 2/5 (40.0%) atypical carcinoid tumors"

Quantifies SSTR2 expression across thymic epithelial tumor histologies including the neuroendocrine subtypes.

🔀

Differential Diagnoses

4

Conditions with similar clinical presentations that must be differentiated from Thymic Neuroendocrine Carcinoma:

Thymoma MONDO:0006456

Overlapping Features The other major thymic epithelial tumor family and the principal anterior-mediastinal differential. Curated separately in kb/disorders/Thymoma.yaml; deliberately not duplicated here.

Distinguishing Features

Thymoma is organotypic and contains immature TdT-positive thymocytes; thymic neuroendocrine carcinoma does not.
Thymoma carries the classic autoimmune paraneoplastic syndromes (myasthenia gravis, pure red cell aplasia, Good syndrome); thymic neuroendocrine carcinoma instead carries the ectopic ACTH/Cushing endocrine syndrome.
Thymoma lacks chromogranin A / synaptophysin neuroendocrine marker expression.
Thymoma typically shows a PD-L1-high phenotype, whereas PD-L1 staining was absent across a series of thymic carcinoids.

Show evidence (1 reference)

PMID:34695605 SUPPORT Other

"thymomas and most thymic carcinomas lack currently targetable mutations, have an extraordinarily low tumor mutational burden, but typically have a programmed death-ligand 1high phenotype"

Establishes the PD-L1-high phenotype of thymoma, which distinguishes it from the PD-L1-negative thymic carcinoid. Evidence source is OTHER because this is a classification review.

Thymic carcinoma (non-neuroendocrine) MONDO:0006451

Overlapping Features Overtly malignant, non-organotypic thymic epithelial carcinoma, predominantly squamous cell type. Curated separately in kb/disorders/Thymic_Carcinoma.yaml; deliberately not duplicated here. Note that MONDO places thymic neuroendocrine carcinoma beneath thymic carcinoma, so this is a parent entity as well as a practical differential.

Distinguishing Features

Thymic squamous cell carcinoma characteristically coexpresses CD5 and CD117 (KIT). CD5 is not a feature of the neuroendocrine arm; CD117/KIT is less discriminating, since a proportion of neuroendocrine tumors are also KIT-positive, so this marker pair should not be used alone.
Genomics differ - conventional thymic carcinoma is dominated by CDKN2A, TP53, ASXL1 and CDKN2B alterations, whereas thymic neuroendocrine neoplasms are dominated by MEN1, MLL2, APC, RB1 and TSC2.
Neuroendocrine marker expression (chromogranin A, synaptophysin) is required for the neuroendocrine designation.

Show evidence (2 references)

PMID:37749819 SUPPORT Human Clinical

"The mutational profiles between TCs and TNENs were diverse."

Panel sequencing establishing that thymic carcinoma and thymic neuroendocrine neoplasms have distinct mutational profiles, supporting their separation as entities.

PMID:37749819 SUPPORT Human Clinical

"The genetic alterations that ranked highest in TCs were in CDKN2A, TP53, ASXL1, CDKN2B, PIK3C2G, PTCH1, and ROS1"

Gives the thymic carcinoma gene ranking that contrasts with the MEN1/MLL2/APC/RB1 ranking of thymic neuroendocrine neoplasms.

Mediastinal paraganglioma Not Yet Curated MONDO:0000448

Overlapping Features A neuroendocrine mediastinal neoplasm that mimics thymic carcinoid morphologically but is of neural crest rather than epithelial origin.

Distinguishing Features

Paraganglioma is pancytokeratin-negative and frequently GATA-3-positive; thymic neuroendocrine carcinoma is universally pancytokeratin-positive and GATA-3-negative.

Show evidence (1 reference)

PMID:25294372 SUPPORT Human Clinical

"All paragangliomas were universally positive for chromogranin A and synaptophysin, but negative for pancytokeratin, TTF-1, and napsin A. GATA-3 was expressed in 12 (55%) of 22 tumors."

Directly supports the pancytokeratin/GATA-3 immunophenotype that separates paraganglioma from thymic neuroendocrine carcinoma.

Metastatic or directly invading pulmonary neuroendocrine carcinoma Not Yet Curated MONDO:0005454

Overlapping Features Small cell and large cell neuroendocrine carcinoma of the lung can involve the anterior mediastinum by direct extension or nodal metastasis, and is far commoner than a primary thymic neuroendocrine carcinoma.

Distinguishing Features

TTF-1 positivity favours a pulmonary primary; only a minority (about 17%) of thymic neuroendocrine carcinomas are TTF-1 positive.
Radiological demonstration of a dominant pulmonary lesion, and absence of a thymus-centred prevascular mass, favours pulmonary origin.

Show evidence (1 reference)

PMID:25294372 PARTIAL Human Clinical

"TTF-1 in 4 (17%) of 24 cases"

Quantifies TTF-1 positivity in thymic neuroendocrine carcinoma, which limits but does not eliminate TTF-1 as a discriminator from pulmonary primaries.

🔬

Clinical Trials

2

NCT06121271 PHASE_II RECRUITING

Open, single-site phase 2 trial of 177Lu-DOTATATE (Lutathera) in unresectable or metastatic somatostatin-receptor-expressing neuroendocrine tumours in currently unlicensed indications, explicitly including thymic NET. Target accrual 75-110 participants receiving four cycles at 8-12 week intervals, with two years of follow-up. This is the main prospective study directly relevant to PRRT in thymic neuroendocrine carcinoma.

Show evidence (1 reference)

clinicaltrials:NCT06121271 SUPPORT Human Clinical

"This study is a phase 2, open, single-site trial. The primary objective of this study is to prospectively evaluate the safety and efficacy in participants treated with Lu-177 DOTATATE (Lutathera) in unresectable or metastatic, somatostatin receptor-expressing neuroendocrine tumours (NET) in..."

Registry record establishing the design, phase and thymic-NET relevance of the trial.

NCT05061784 NOT_APPLICABLE COMPLETED

Completed observational case series revisiting the evidence for routine transcervical thymectomy as prophylaxis against thymic carcinoid in MEN1 patients, built on a four-database literature review. Relevant to the prevention question rather than to treatment of established disease.

Show evidence (1 reference)

clinicaltrials:NCT05061784 SUPPORT Human Clinical

"A case series was built after review of available literature by searching four databases (PubMed, Embase, Medline and Cochrane Library) for observational studies or case reports on routine prophylactic TCT for MEN-1 and the development of thymic carcinoids."

Registry record establishing the design and scope of the study.

{ }

Source YAML

click to show

name: Thymic Neuroendocrine Carcinoma
creation_date: "2026-07-31T00:00:00Z"
description: >-
  Thymic neuroendocrine carcinoma (thymic neuroendocrine neoplasm, historically
  "thymic carcinoid") is an ultra-rare thymic epithelial malignancy of the
  prevascular (anterior) mediastinum that shows neuroendocrine morphology and
  expresses neuroendocrine markers (chromogranin A, synaptophysin). It spans a
  graded spectrum from well-differentiated typical carcinoid through atypical
  carcinoid to poorly differentiated large cell neuroendocrine carcinoma and
  small cell carcinoma of the thymus. Three features distinguish it from the two
  other thymic epithelial tumor families curated separately in dismech: (1) a
  strong association with germline MEN1 loss - roughly a quarter to a third of
  cases arise in multiple endocrine neoplasia type 1, where thymic disease is a
  leading cause of syndrome-related mortality; (2) functional endocrine
  paraneoplasia, most characteristically ectopic ACTH/CRH secretion producing
  Cushing syndrome; and (3) a marked male predominance. Unlike thymoma, it does
  not carry the classic thymoma autoimmune syndromes (myasthenia gravis, pure
  red cell aplasia); and unlike thymic squamous cell carcinoma it lacks the
  CDKN2A/TP53-dominant mutational profile, being instead enriched for MEN1, MLL2
  (KMT2D), APC, RB1 and TSC2 alterations. Behaviour is aggressive relative to thymoma, with frequent
  nodal, osseous, pulmonary and pleural metastasis and late recurrence even after
  complete resection.
category: Neoplastic
categories:
- Neuroendocrine Cancer
- Thymic epithelial tumor
- Mediastinal neoplasm
- Thoracic cancer
parents:
- thymic epithelial neoplasm
- neuroendocrine carcinoma
- thymus cancer
synonyms:
- thymic neuroendocrine neoplasm
- thymic neuroendocrine tumor
- neuroendocrine carcinoma of thymus
- thymic carcinoid
disease_term:
  preferred_term: thymic neuroendocrine carcinoma
  term:
    id: MONDO:0020516
    label: thymic neuroendocrine carcinoma
mappings:
  mondo_mappings:
  - term:
      id: MONDO:0020516
      label: thymic neuroendocrine carcinoma
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
  - term:
      id: MONDO:0019964
      label: thymic neuroendocrine tumor
    mapping_predicate: skos:broadMatch
    mapping_source: MONDO
    mapping_justification: >-
      MONDO:0019964 is the parent thymic neuroendocrine tumor class; this entry is
      scoped to MONDO:0020516 but draws evidence from series reported under the
      broader label.
  ncit_mappings:
  - term:
      id: NCIT:C171031
      label: Thymus Neuroendocrine Carcinoma
    mapping_predicate: skos:exactMatch
    mapping_source: MONDO
    mapping_justification: >-
      MONDO:0020516 carries NCIT:C171031 as an xref.
  icd11f_mappings:
  - term:
      id: icd11f:381956131
      label: Carcinoid tumour or other neuroendocrine neoplasms of thymus
    mapping_predicate: skos:exactMatch
    mapping_source: ORPHA:99869
    mapping_justification: >-
      Orphanet lists ICD-11 2C27.1 as an exact cross-reference for ORPHA:99869
      (thymic neuroendocrine carcinoma); the local ICD-11 Foundation ontology
      represents this as icd11f:381956131.
    consistency:
    - reference: ORPHA:99869
      consistent: CONSISTENT
      notes: >-
        The Orphanet cross-reference table for ORPHA:99869 carries the row
        "ICD-11:2C27.1 | Exact".
classifications:
  harrisons_chapter:
  - classification_value: ONCOLOGY_HEMATOLOGY
    notes: >-
      Primary clinical home is thoracic/endocrine oncology; thymic neuroendocrine
      carcinoma is a malignant epithelial neoplasm.
  - classification_value: ENDOCRINOLOGY_METABOLISM
    notes: >-
      Secondary Part assignment reflecting the functional endocrine axis (ectopic
      ACTH/CRH-driven Cushing syndrome) and the MEN1 predisposition-syndrome
      context.
  icdo_morphology:
    classification_value: Carcinoma
    notes: >-
      ICD-O morphology family. The specific ICD-O-3 morphology codes used for this
      family are 8240/3 (typical carcinoid), 8249/3 (atypical carcinoid), 8013/3
      (large cell neuroendocrine carcinoma) and 8041/3 (small cell carcinoma),
      each with topography C37.9 (thymus).
references:
- reference: PMID:20301710
  title: "Multiple Endocrine Neoplasia Type 1."
  tags:
  - GeneReviews
- reference: PMID:34695605
  title: "The 2021 WHO Classification of Tumors of the Thymus and Mediastinum: What Is New in Thymic Epithelial, Germ Cell, and Mesenchymal Tumors?"
- reference: PMID:40068632
  title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
- reference: ORPHA:99869
  title: "Thymic neuroendocrine carcinoma"
notes: >-
  Scope and boundary. This entry covers only the neuroendocrine arm of thymic
  epithelial neoplasia. Conventional (non-neuroendocrine) thymic carcinoma -
  overwhelmingly thymic squamous cell carcinoma, with its CD5/CD117
  immunophenotype and CDKN2A/TP53-dominant genomics - is curated in
  kb/disorders/Thymic_Carcinoma.yaml, which retains a "Neuroendocrine" subtype
  facet for taxonomic completeness only; the mechanistic content lives here.
  Thymoma, an organotypic thymic epithelial tumor with a distinct autoimmune
  paraneoplastic profile (myasthenia gravis, pure red cell aplasia, Good
  syndrome), is curated in kb/disorders/Thymoma.yaml. Both are modeled here as
  differential diagnoses rather than being duplicated.

  Terminology caveat. The literature uses "thymic neuroendocrine carcinoma",
  "thymic neuroendocrine neoplasm/tumor" and "thymic carcinoid" close to
  interchangeably, and MONDO:0020516 sits over the whole graded family (MONDO
  places both the well-differentiated carcinoids and the poorly differentiated
  small cell / large cell forms beneath it). Evidence in this entry is therefore
  drawn from series reported under all of those labels; where a finding is
  specific to one grade the subtype is named in the record.

  Deep research provenance. Curated with an Edison/Falcon deep-research report
  (research/Thymic_Neuroendocrine_Carcinoma-deep-research-falcon.md) used as
  leads only. That report returned no usable primary PMIDs and proposed several
  incorrect ontology identifiers (HP:0002664 offered for "Cushing syndrome" is
  actually Neoplasm; HP:0000846 offered for "hypercortisolism" is actually
  Adrenal insufficiency; UBERON:0003406 offered for "mediastinum" is actually
  cartilage of respiratory system). Every term used here was independently
  verified with OAK and every snippet against the cached abstract.
has_subtypes:
- name: Typical carcinoid
  display_name: Thymic typical carcinoid (well-differentiated, NET G1)
  subtype_term:
    preferred_term: well-differentiated thymic neuroendocrine carcinoma
    term:
      id: MONDO:0016976
      label: well-differentiated thymic neuroendocrine carcinoma
  description: >-
    Well-differentiated thymic neuroendocrine neoplasm with organoid architecture,
    low mitotic count and no necrosis. It is the rarest grade in the thymus -
    unlike the lung, where typical carcinoid predominates, the vast majority of
    thymic carcinoids are atypical. Clinically the most indolent grade, but late
    recurrence still occurs.
  locations:
  - preferred_term: thymus
    term:
      id: UBERON:0002370
      label: thymus
  evidence:
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Regarding the tumor classification, our results showed that a vast majority
      of carcinoids in the thymus correspond to ACs. In addition, our results also
      indicate that typical carcinoid is a very rare entity.
    explanation: >-
      Surgical series supports typical carcinoid as the rarest grade of thymic
      neuroendocrine neoplasm, in contrast to the pulmonary distribution.
- name: Atypical carcinoid
  display_name: Thymic atypical carcinoid (moderately differentiated, NET G2/G3)
  subtype_term:
    preferred_term: moderately-differentiated thymic neuroendocrine carcinoma
    term:
      id: MONDO:0016977
      label: moderately-differentiated thymic neuroendocrine carcinoma
  description: >-
    The dominant grade of thymic neuroendocrine neoplasm. Retains carcinoid
    (organoid) architecture but shows an elevated mitotic count and/or punctate
    necrosis. In contemporary practice a subset with high proliferation is further
    separated as "NET G3 highly proliferative atypical carcinoid". Atypical
    carcinoids present at higher stage than typical carcinoids and account for
    most ectopic-Cushing and most MEN1-associated thymic disease.
  locations:
  - preferred_term: thymus
    term:
      id: UBERON:0002370
      label: thymus
  evidence:
  - reference: PMID:30502716
    reference_title: "Carcinoid tumors of the thymus and Cushing's syndrome: Clinicopathologic features and current best evidence regarding the cell of origin of these unusual neoplasms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The incidence of Masaoka stage IV was higher (p < 0.0001) in patients with
      ATC than TC.
    explanation: >-
      Directly supports higher-stage presentation of atypical carcinoid relative
      to typical carcinoid in a thymic carcinoid series.
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      NET G2 atypical carcinoids in 31 patients (48%), 20 patients (31%) with NET
      G3 highly proliferative atypical carcinoids
    explanation: >-
      The French national-network series shows atypical carcinoid (G2 plus highly
      proliferative G3) accounting for about 79% of advanced thymic NET.
- name: LCNEC
  display_name: Thymic large cell neuroendocrine carcinoma
  subtype_term:
    preferred_term: thymic large cell neuroendocrine carcinoma
    term:
      id: MONDO:0003047
      label: thymic large cell neuroendocrine carcinoma
  description: >-
    Poorly differentiated, non-small-cell high-grade thymic neuroendocrine
    carcinoma with a high mitotic rate and almost invariable necrosis. Behaves
    aggressively; can arise in MEN1 as well as sporadically.
  locations:
  - preferred_term: thymus
    term:
      id: UBERON:0002370
      label: thymus
  evidence:
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All the patients (3/3) with large cell NEC (3/3) and 16.7% (3/18) of those
      with AC died of tumor progression.
    explanation: >-
      Supports the markedly worse outcome of thymic large cell neuroendocrine
      carcinoma relative to atypical carcinoid in the same series.
  - reference: PMID:35696052
    reference_title: "Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      One patient had a largely necrotic main tumor with very few mitoses and
      another nodule with 25 mitoses per 2 mm2, qualifying for the 2021 WHO
      diagnosis of large cell neuroendocrine carcinoma (LCNEC).
    explanation: >-
      Documents LCNEC occurring within a MEN1 thymic neuroendocrine tumor cohort.
- name: Small cell carcinoma
  display_name: Small cell carcinoma of the thymus (neuroendocrine type)
  subtype_term:
    preferred_term: thymus small cell carcinoma
    term:
      id: MONDO:0004122
      label: thymus small cell carcinoma
  description: >-
    Poorly differentiated small-cell high-grade thymic neuroendocrine carcinoma
    with a high mitotic rate and numerous apoptotic bodies. Managed by
    extrapolation from small cell lung carcinoma with platinum-etoposide
    chemotherapy; a primary thymic origin must be established by excluding
    pulmonary or mediastinal-nodal small cell carcinoma.
  locations:
  - preferred_term: thymus
    term:
      id: UBERON:0002370
      label: thymus
  evidence:
  - reference: PMID:29049806
    reference_title: "Results of treatment for thymic neuroendocrine tumours: multicentre clinicopathological study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The examined tumours were classified as typical carcinoid in 7 patients,
      atypical carcinoid in 11 patients, large-cell neuroendocrine carcinoma in 3
      patients and small-cell carcinoma in 9 patients
    explanation: >-
      Multicentre surgical series enumerating all four WHO grades of thymic
      neuroendocrine neoplasm, including small cell carcinoma of the thymus.
pathophysiology:
- name: Menin Tumor Suppressor Loss
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    Biallelic inactivation of MEN1, which encodes the chromatin-adaptor tumor
    suppressor menin, is the best-established initiating lesion of thymic
    neuroendocrine neoplasia. In multiple endocrine neoplasia type 1 a germline
    loss-of-function MEN1 variant is followed by somatic loss of the remaining
    allele in the thymic precursor; MEN1 is also the top-ranked somatically
    altered gene in thymic neuroendocrine neoplasms overall. Roughly a quarter to
    a third of thymic neuroendocrine neoplasms arise on a MEN1 background, and
    thymic disease is a disproportionate contributor to MEN1 mortality.
  genes:
  - preferred_term: MEN1
    term:
      id: hgnc:7010
      label: MEN1
  locations:
  - preferred_term: thymus
    term:
      id: UBERON:0002370
      label: thymus
  cell_types:
  - preferred_term: thymic epithelial cell with neuroendocrine differentiation
    term:
      id: CL:0002293
      label: epithelial cell of thymus
  evidence:
  - reference: PMID:40068632
    reference_title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      About 25% of the tumors are related to multiple endocrine neoplasia type I
      (MEN-1), where they contribute significantly to mortality.
    explanation: >-
      Clinical review quantifying the MEN1 fraction of thymic neuroendocrine
      neoplasms and its mortality impact. Evidence source is OTHER because this is
      a narrative review.
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those in TNENs were in MEN1, MLL2, APC, RB1
    explanation: >-
      Targeted panel sequencing of 15 thymic neuroendocrine neoplasms ranks MEN1
      as the most frequently altered gene, supporting menin loss as the dominant
      molecular lesion of this tumor family.
  downstream:
  - target: Neuroendocrine Clonal Expansion in the Thymus
    description: >-
      Loss of menin-dependent transcriptional restraint permits clonal outgrowth
      of a thymic epithelial cell with neuroendocrine differentiation.
- name: RB-Axis Tumor Suppressor Loss
  biological_scale: MOLECULAR
  role: trigger
  conforms_to: "evading_growth_suppressors#Tumor Suppressor Inactivation"
  description: >-
    RB1 is among the top-ranked somatically altered genes in thymic neuroendocrine
    neoplasms. Loss of the RB axis removes the antiproliferative brake that gates
    G1/S transit - the conserved hallmark route modeled in the
    evading_growth_suppressors module. This node is the entry point for the
    high-grade (large cell neuroendocrine carcinoma and small cell) end of the
    spectrum, where the classic poorly differentiated neuroendocrine RB1/TP53-loss
    biology applies.
  genes:
  - preferred_term: RB1
    term:
      id: hgnc:9884
      label: RB1
  biological_processes:
  - preferred_term: regulation of cell cycle
    term:
      id: GO:0051726
      label: regulation of cell cycle
    modifier: ABNORMAL
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 .
    explanation: >-
      Panel sequencing of 15 thymic neuroendocrine neoplasms ranks this gene among
      the top clinically relevant genomic alterations in the tumor family.
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Further investigation found that the prognosis-related genes were focused on
      signal pathways of cell cycle control, chromatin remodeling/DNA methylation
    explanation: >-
      Supports cell-cycle control as one of the pathways in which the
      prognostically important thymic malignancy lesions concentrate.
  notes: >-
    Conformance caveat. The conforms_to link is asserted at the module's trigger
    node on the strength of thymus-specific panel-sequencing data showing recurrent
    RB1 alteration - RB1 is squarely inside the module's RB/p53-axis scope. The
    other recurrently altered thymic neuroendocrine tumor suppressors (KMT2D, APC,
    TSC2) are deliberately modeled as separate nodes because they are not RB/p53
    axis lesions. Downstream checkpoint-loss mechanics in thymic neuroendocrine
    carcinoma specifically have not been dissected experimentally and are
    extrapolated from pulmonary and extrapulmonary high-grade neuroendocrine
    carcinoma; the disease-specific edge is therefore not asserted beyond the
    proliferation node.
  downstream:
  - target: Neuroendocrine Clonal Expansion in the Thymus
    description: >-
      Loss of cell-cycle-checkpoint control permits unrestrained proliferation of
      the transformed thymic neuroendocrine clone.
- name: Chromatin Regulator Loss
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    MLL2 (KMT2D), a histone H3K4 methyltransferase, and APC are recurrently
    altered in thymic neuroendocrine neoplasms, and the prognostically important
    lesions in thymic malignancy concentrate in chromatin-remodelling/DNA-methylation
    pathways. This is mechanistically congruent with the chromatin-adaptor function
    of menin, and is modeled separately from the RB axis because H3K4-methylation
    and Wnt lesions are not RB/p53-axis tumor-suppressor inactivation.
  genes:
  - preferred_term: KMT2D
    term:
      id: hgnc:7133
      label: KMT2D
  - preferred_term: APC
    term:
      id: hgnc:583
      label: APC
  molecular_functions:
  - preferred_term: histone H3K4 methyltransferase activity
    term:
      id: GO:0042800
      label: histone H3K4 methyltransferase activity
    modifier: DECREASED
  biological_processes:
  - preferred_term: chromatin organization
    term:
      id: GO:0006325
      label: chromatin organization
    modifier: ABNORMAL
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 .
    explanation: >-
      Panel sequencing of 15 thymic neuroendocrine neoplasms ranks this gene among
      the top clinically relevant genomic alterations in the tumor family.
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Further investigation found that the prognosis-related genes were focused on
      signal pathways of cell cycle control, chromatin remodeling/DNA methylation
    explanation: >-
      Supports chromatin remodelling / DNA methylation as a pathway in which the
      prognostically important thymic malignancy lesions concentrate.
  downstream:
  - target: Neuroendocrine Clonal Expansion in the Thymus
    description: >-
      Loss of chromatin-regulatory restraint contributes to the transformed
      transcriptional program of the expanding neuroendocrine clone.
- name: mTOR Pathway Restraint Loss
  biological_scale: MOLECULAR
  role: trigger
  description: >-
    TSC2 is among the recurrently altered genes in thymic neuroendocrine
    neoplasms. TSC2 encodes tuberin, which with hamartin restrains RHEB and hence
    mTORC1; its loss releases that restraint and drives constitutive TOR
    signalling. This node - not the RB axis - is the mechanistic rationale for
    mTOR-inhibitor (everolimus) therapy in this tumor family.
  genes:
  - preferred_term: TSC2
    term:
      id: hgnc:12363
      label: TSC2
  biological_processes:
  - preferred_term: TOR signaling
    term:
      id: GO:0031929
      label: TOR signaling
    modifier: INCREASED
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those in TNENs were in MEN1, MLL2, APC, RB1 , and TSC2 .
    explanation: >-
      Panel sequencing of 15 thymic neuroendocrine neoplasms ranks this gene among
      the top clinically relevant genomic alterations in the tumor family.
  downstream:
  - target: Neuroendocrine Clonal Expansion in the Thymus
    description: >-
      Unrestrained mTORC1 signalling drives the growth and proliferation of the
      transformed thymic neuroendocrine clone.
- name: Neuroendocrine Clonal Expansion in the Thymus
  biological_scale: CELLULAR
  role: central_effector
  description: >-
    A thymic epithelial cell acquires or retains neuroendocrine differentiation
    and expands clonally in the prevascular mediastinum. The resulting neoplastic
    cells are pancytokeratin-positive (confirming epithelial lineage, and
    distinguishing them from paraganglioma) while co-expressing the neuroendocrine
    markers chromogranin A and synaptophysin. Proliferative activity - mitotic
    count and Ki-67 index - grades the lesion and is the marker most consistently
    associated with outcome, although in the same series overall staining for the
    wider biomarker panel did not associate with survival or grade.
  cell_types:
  - preferred_term: thymic neuroendocrine tumor cell
    term:
      id: CL:0000165
      label: neuroendocrine cell
  biological_processes:
  - preferred_term: neuroendocrine cell differentiation
    term:
      id: GO:0061101
      label: neuroendocrine cell differentiation
    modifier: ABNORMAL
  - preferred_term: cell population proliferation
    term:
      id: GO:0008283
      label: cell population proliferation
    modifier: INCREASED
  locations:
  - preferred_term: anterior mediastinum
    term:
      id: UBERON:0008820
      label: anterior mediastinum
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The thymic neuroendocrine carcinomas (carcinoid tumors) were universally
      positive for pancytokeratin, but negative for GATA-3 and napsin A.
      Chromogranin A and synaptophysin were expressed in 92% and 88% of cases,
      respectively
    explanation: >-
      Immunohistochemical series of 24 thymic neuroendocrine carcinomas supports
      an epithelial cell of origin with neuroendocrine marker expression.
  - reference: PMID:33243039
    reference_title: "Typical and Atypical Carcinoid Tumors of the Mediastinum: A Biomarker Analysis of 27 Cases With Clinical Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ki-67 expression ≥1% associated with DoD (P = .003) and death within 5 years
      (P = .031).
    explanation: >-
      Supports proliferative activity (Ki-67 index) as associated with death of
      disease in thymic carcinoid.
  - reference: PMID:33243039
    reference_title: "Typical and Atypical Carcinoid Tumors of the Mediastinum: A Biomarker Analysis of 27 Cases With Clinical Correlation."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Overall ± staining did not associate with survival or grade.
    explanation: >-
      Boundary condition on the preceding claim: in the same 27-case series the
      wider immunohistochemical panel, unlike Ki-67 and mitotic count, showed no
      association with survival or grade.
  downstream:
  - target: Ectopic Corticotropin and CRH Secretion
    description: >-
      The expanded neuroendocrine clone retains and amplifies the ACTH/CRH
      secretory program of its thymic cell of origin.
  - target: Somatostatin Receptor Expression
    description: >-
      Neuroendocrine differentiation includes surface somatostatin receptor
      expression, the substrate for SSTR imaging and SSTR-directed therapy.
  - target: Mediastinal Mass Effect and Local Invasion
    description: >-
      Clonal expansion produces a prevascular mediastinal mass that compresses and
      invades adjacent thoracic structures.
  - target: Nodal and Distant Metastatic Dissemination
    description: >-
      Proliferating tumor cells disseminate via lymphatics and blood to nodes,
      bone, lung and pleura.
  - target: Thymic neuroendocrine tumor
    description: >-
      The expanded clone constitutes the defining lesion, a neuroendocrine neoplasm
      of the thymus.
- name: Ectopic Corticotropin and CRH Secretion
  biological_scale: CELLULAR
  role: consequence
  description: >-
    The normal thymus contains scattered ACTH- and CRH-immunoreactive cells, and
    thymic neuroendocrine tumors are correspondingly immunoreactive for both
    hormones; tumors from patients with Cushing syndrome stain more strongly for
    both than those without. Autonomous, non-pituitary secretion of ACTH (with a
    probable contribution from tumoral CRH) drives bilateral adrenocortical
    stimulation and ACTH-dependent hypercortisolism. This is the signature
    functional paraneoplastic syndrome of the thymic neuroendocrine family and
    frequently brings the tumor to attention before it is otherwise symptomatic.
  biological_processes:
  - preferred_term: corticotropin secretion
    term:
      id: GO:0051458
      label: corticotropin secretion
    modifier: INCREASED
  - preferred_term: peptide hormone secretion
    term:
      id: GO:0030072
      label: peptide hormone secretion
    modifier: INCREASED
  cell_types:
  - preferred_term: thymic neuroendocrine tumor cell
    term:
      id: CL:0000165
      label: neuroendocrine cell
  evidence:
  - reference: PMID:30502716
    reference_title: "Carcinoid tumors of the thymus and Cushing's syndrome: Clinicopathologic features and current best evidence regarding the cell of origin of these unusual neoplasms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ten NET were CRH immunoreactive and 6 were ACTH immunoreactive. Thymic NET
      with CS exhibited stronger immunoreactivity for ACTH and CRH than those
      without CS.
    explanation: >-
      Directly links tumoral ACTH and CRH production to the presence of Cushing
      syndrome in thymic neuroendocrine tumors.
  - reference: PMID:30502716
    reference_title: "Carcinoid tumors of the thymus and Cushing's syndrome: Clinicopathologic features and current best evidence regarding the cell of origin of these unusual neoplasms."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The thymus contains CRH and ACTH immunoreactive cells that are probably the
      origin of thymic NET.
    explanation: >-
      Supports a normal thymic ACTH/CRH-immunoreactive cell as the proposed cell of
      origin, explaining why the ectopic-ACTH syndrome is characteristic of this
      tumor family.
  - reference: PMID:37409236
    reference_title: "Expressions of Cushing's syndrome in multiple endocrine neoplasia type 1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Ectopic tumoral ACTH secretion has also been observed in MEN1, almost
      exclusively originating from thymic neuroendocrine tumors.
    explanation: >-
      Review establishing that within MEN1, ectopic ACTH secretion comes almost
      exclusively from thymic neuroendocrine tumors, underscoring how
      characteristic this mechanism is of the entity. Evidence source is OTHER
      because this is a narrative review.
  downstream:
  - target: ACTH-Dependent Hypercortisolism
    description: >-
      Autonomous tumoral ACTH secretion escapes pituitary negative feedback and
      drives sustained adrenocortical cortisol output.
- name: ACTH-Dependent Hypercortisolism
  biological_scale: ORGANISM
  role: consequence
  description: >-
    Sustained non-pituitary ACTH stimulation of the adrenal cortex produces
    ACTH-dependent (secondary) hypercortisolism with the ectopic Cushing syndrome
    phenotype - hypertension, hypokalaemic metabolic alkalosis, hyperglycaemia,
    proximal myopathy, osteoporosis and immunosuppression with opportunistic
    infection. In thymic neuroendocrine tumors this hormonal morbidity is a
    substantial and sometimes dominant contributor to mortality independent of
    tumor bulk, and its control is an urgent management priority.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      11 patients (15%) with ectopic Cushing syndrome
    explanation: >-
      Quantifies ectopic Cushing syndrome in 15% of a 74-patient advanced thymic
      NET cohort.
  downstream:
  - target: Ectopic ACTH-dependent Cushing syndrome
    description: >-
      Sustained ACTH-driven cortisol excess manifests clinically as ectopic Cushing
      syndrome.
  - target: Hypertension
    description: >-
      Cortisol excess cross-activates the mineralocorticoid receptor, raising blood
      pressure.
  - target: Hypokalemia
    description: >-
      Cortisol overwhelms renal 11-beta-HSD2, driving mineralocorticoid-like
      kaliuresis and hypokalaemic alkalosis.
- name: Somatostatin Receptor Expression
  biological_scale: MOLECULAR
  role: consequence
  description: >-
    A substantial fraction of thymic neuroendocrine neoplasms express membranous
    somatostatin receptor 2 (SSTR2). SSTR2 expression is the molecular substrate
    for somatostatin-receptor functional imaging (68Ga-DOTATATE PET) and for
    SSTR-directed therapy with somatostatin analogues and peptide receptor
    radionuclide therapy, and expression level tracks with imaging avidity. In
    advanced thymic NET, somatostatin-receptor imaging is positive in roughly
    three-quarters of cases.
  biological_processes:
  - preferred_term: somatostatin receptor signaling pathway
    term:
      id: GO:0038169
      label: somatostatin receptor signaling pathway
    modifier: ABNORMAL
  cell_types:
  - preferred_term: thymic neuroendocrine tumor cell
    term:
      id: CL:0000165
      label: neuroendocrine cell
  evidence:
  - reference: PMID:35198446
    reference_title: "Correlation of Somatostatin Receptor 2 Expression, 68Ga-DOTATATE PET Scan and Octreotide Treatment in Thymic Epithelial Tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      68Ga-DOTATATE PET scans correlated with SSTR2 expression in TET in most
      patients and appeared to be useful to identify patients with TET who may be
      amenable to treatment with somatostatin analogues.
    explanation: >-
      Supports SSTR2 expression as the basis of DOTATATE imaging avidity and of
      somatostatin-analogue treatment selection in thymic epithelial tumors,
      including atypical carcinoid and small cell carcinoma.
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Positive results for 18F-FDG or somatostain receptor imaging was found in 88%
      or 74% of cases, respectively.
    explanation: >-
      Quantifies somatostatin-receptor imaging positivity in 74% of advanced thymic
      NET, supporting SSTR expression as a common tumor feature.
- name: Mediastinal Mass Effect and Local Invasion
  biological_scale: TISSUE
  role: consequence
  description: >-
    The tumor grows as a prevascular (anterior) mediastinal mass and invades
    mediastinal fat, pleura, pericardium, lung and great vessels, producing chest
    pain, cough, dyspnoea and occasionally superior vena caval obstruction. Most
    patients with advanced disease present with locally advanced rather than
    synchronously metastatic tumor, and completeness of resection is the single
    strongest modifiable prognostic factor.
  locations:
  - preferred_term: anterior mediastinum
    term:
      id: UBERON:0008820
      label: anterior mediastinum
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A total of 64 patients (87%) had locally advanced Thy-NET and eight (11%) had
      synchronous metastases, at diagnosis.
    explanation: >-
      Supports locally advanced mediastinal disease as the dominant presentation
      pattern of advanced thymic NET.
  - reference: PMID:29049806
    reference_title: "Results of treatment for thymic neuroendocrine tumours: multicentre clinicopathological study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Overall survival was significantly better in patients who underwent
      macroscopic complete resection (P = 0.010).
    explanation: >-
      Supports resectability of the local mediastinal tumor as the key determinant
      of survival.
  downstream:
  - target: Anterior mediastinal mass
    description: >-
      The expanding tumor is detected radiologically as a prevascular mediastinal
      mass.
  - target: Chest pain
    description: >-
      Invasion of pleura, pericardium and chest wall produces chest pain.
  - target: Dyspnea
    description: >-
      Compression or invasion of airway, lung and great vessels causes
      breathlessness.
  - target: Cough
    description: >-
      Airway irritation and compression by the mediastinal mass produces cough.
- name: Nodal and Distant Metastatic Dissemination
  biological_scale: ORGANISM
  role: outcome
  description: >-
    Thymic neuroendocrine carcinoma disseminates to regional mediastinal lymph
    nodes and then to bone, lung, pleura, liver and brain. Metastasis is frequently
    metachronous - appearing years after an apparently complete resection - which
    is why prolonged surveillance is required even for well-differentiated tumors.
    Pleural spread appears to be almost exclusively metachronous and may reflect
    perioperative dissemination. In MEN1-associated disease the
    metachronous-metastasis rate is very high.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Metastatic sites were as follows: lymph nodes (54 patients, 73%), bone (42
      patients, 65%), lung (31 patients, 42%), and pleura (31 patients, 42%).
    explanation: >-
      Enumerates the metastatic site distribution of advanced thymic NET.
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Eighty nine percent of patients developed a metachronous metastasis from the
      thymic carcinoid.
    explanation: >-
      Supports the predominance of metachronous (late) metastasis in
      MEN1-associated thymic carcinoid.
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pleural metastases were almost exclusively metachronous.
    explanation: >-
      Supports the distinctive metachronous timing of pleural spread; the same
      cohort's discussion raises perioperative dissemination as the suspected
      explanation.
  downstream:
  - target: Mediastinal lymphadenopathy
    description: >-
      Regional nodal spread presents as mediastinal lymphadenopathy, the commonest
      metastatic site.
  - target: Bone metastasis
    description: >-
      Haematogenous spread to the skeleton produces bone metastases and bone pain.
  - target: Pulmonary metastasis
    description: >-
      Haematogenous spread seeds the lung, one of the commonest distant sites.
  - target: Pleural metastasis
    description: >-
      Pleural seeding, almost always metachronous, follows local and perioperative
      dissemination.
  - target: Hepatic metastasis
    description: >-
      Haematogenous spread seeds the liver, a common distant site.
  - target: Cerebral metastasis
    description: >-
      Haematogenous spread seeds the brain, a recognised distant site that alters
      surveillance imaging and systemic-therapy choice.
  - target: Weight loss
    description: >-
      Advanced metastatic tumor burden produces constitutional weight loss.
phenotypes:
- category: Neoplasm
  name: Thymic neuroendocrine tumor
  frequency: OBLIGATE
  diagnostic: true
  description: >-
    The defining lesion - a neuroendocrine neoplasm of the thymus. Historically
    labelled thymic carcinoid, it is a malignant thymic epithelial tumor with
    neuroendocrine morphology and marker expression.
  phenotype_term:
    preferred_term: Thymic neuroendocrine neoplasm
    term:
      id: HP:0100521
      label: Neoplasm of the thymus
  notes: >-
    Term choice. HP:0034954 Thymic carcinoid tumor ("A primary thymic
    neuroendocrine tumor") reads as the obvious match on its label, but under
    the 2021 WHO scheme "carcinoid" denotes only the well- and
    moderately-differentiated grades. This entry deliberately spans all four
    grades including large cell neuroendocrine carcinoma and small cell
    carcinoma, which are not carcinoids, so HP:0034954 is narrower than the
    disease it would be annotating. HP:0100521 Neoplasm of the thymus is used
    instead as the nearest term that covers the whole graded spectrum; the
    neuroendocrine qualification is carried by preferred_term and by the
    subtype-level MONDO terms. An HPO NTR for a grade-agnostic "thymic
    neuroendocrine neoplasm" class would resolve this properly.
  evidence:
  - reference: PMID:40068632
    reference_title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Thymic carcinoids or neuroendocrine neoplasms (t-NEN) are a rare entity with
      a dismal prognosis.
    explanation: >-
      Review establishing the entity and its poor prognosis. Evidence source is
      OTHER because this is a narrative review.
  - reference: ORPHA:99869
    reference_title: "Thymic neuroendocrine carcinoma"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Thymic neuroendocrine carcinoma is a type of thymic epithelial neoplasm
      displaying evidence of neuroendocrine differentiation.
    explanation: >-
      Orphanet definition of the entity curated here.
- category: Thoracic
  name: Anterior mediastinal mass
  frequency: OBLIGATE
  diagnostic: true
  description: >-
    The tumor presents as a mass in the prevascular (anterior) mediastinum, often
    large and locally invasive at diagnosis.
  phenotype_term:
    preferred_term: Anterior mediastinal mass
    term:
      id: HP:0033827
      label: Anterior mediastinal mass
  evidence:
  - reference: ORPHA:99869
    reference_title: "Thymic neuroendocrine carcinoma"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Thymic neuroendocrine carcinoma is a type of thymic epithelial neoplasm
      displaying evidence of neuroendocrine differentiation.
    explanation: >-
      A thymic epithelial neoplasm is by definition a prevascular (anterior)
      mediastinal mass, which is why the phenotype is OBLIGATE.
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A total of 64 patients (87%) had locally advanced Thy-NET and eight (11%) had
      synchronous metastases, at diagnosis.
    explanation: >-
      Characterises the mediastinal primary as usually locally advanced at diagnosis.
      Marked PARTIAL because it speaks to stage rather than to the presence of the
      mass.
- category: Endocrine
  name: Ectopic ACTH-dependent Cushing syndrome
  frequency: OCCASIONAL
  description: >-
    Autonomous tumoral ACTH (and CRH) secretion produces ACTH-dependent
    hypercortisolism - the signature functional paraneoplastic syndrome of thymic
    neuroendocrine neoplasms. Reported in 15% of an advanced-disease national
    cohort and in 3 of 21 (14%) of a surgical series, and strongly enriched in
    atypical carcinoid. It is frequently the presenting manifestation and is a
    major independent source of morbidity and mortality. The OCCASIONAL band is
    anchored on those two unselected surgical/registry series; a Cushing-focused
    pathology series reports a much higher 36.4%, but that denominator is
    ascertainment-biased by design and is not used to set the band.
  phenotype_term:
    preferred_term: ACTH-dependent hypercortisolism (ectopic Cushing syndrome)
    term:
      id: HP:0011744
      label: Secondary hypercortisolism
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      11 patients (15%) with ectopic Cushing syndrome
    explanation: >-
      Direct quantitative support for the OCCASIONAL (5-29%) frequency band in a
      74-patient national-network cohort.
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Three cases of atypical carcinoid (AC) were associated with ectopic Cushing's
      syndrome.
    explanation: >-
      Independent surgical series documenting ectopic Cushing syndrome in 3 of 21
      thymic neuroendocrine tumors (14%), consistent with the OCCASIONAL band.
- category: Cardiovascular
  name: Hypertension
  context: Ectopic Cushing syndrome subset
  description: >-
    A cardinal manifestation of the ectopic-ACTH hypercortisolism seen in
    functional thymic neuroendocrine tumors, driven by cortisol's
    mineralocorticoid-receptor cross-activation. Occurs only in the functional
    subset; no thymic-NET-specific frequency is published, so none is asserted.
  phenotype_term:
    preferred_term: Hypertension
    term:
      id: HP:0000822
      label: Hypertension
  evidence:
  - reference: PMID:35690804
    reference_title: "Successful resolution of ectopic Cushing syndrome by minimally invasive thoracoscopic resection of the neuroendocrine tumor of the thymus: a rare case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Physical examination revealed hypertension (blood pressure: 141/100 mmHg). A
      mediastinal tumor was discovered to be the cause of the patient's chronic
      hypokalemia and hypercortisolemia.
    explanation: >-
      Case report of a thymic carcinoid with ectopic ACTH-dependent Cushing
      syndrome documenting hypertension attributable to the tumor.
- category: Metabolic
  name: Hypokalemia
  context: Ectopic Cushing syndrome subset
  description: >-
    Hypokalaemic metabolic alkalosis is characteristic of severe ectopic-ACTH
    hypercortisolism, where very high cortisol overwhelms renal 11-beta-HSD2 and
    activates mineralocorticoid receptors. Occurs only in the functional subset;
    no thymic-NET-specific frequency is published, so none is asserted.
  phenotype_term:
    preferred_term: Hypokalemia
    term:
      id: HP:0002900
      label: Hypokalemia
  evidence:
  - reference: PMID:35690804
    reference_title: "Successful resolution of ectopic Cushing syndrome by minimally invasive thoracoscopic resection of the neuroendocrine tumor of the thymus: a rare case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The presence of hypertension, hypokalemia, and alkalinity suggested Cushing's
      syndrome, which was proven to be ACTH-dependent ECS by a dexamethasone
      suppression test.
    explanation: >-
      Documents the hypertension-hypokalaemia-alkalosis triad of ACTH-dependent
      ectopic Cushing syndrome arising from a thymic neuroendocrine tumor.
- category: Thoracic
  name: Chest pain
  description: >-
    Local invasion of mediastinal structures, pleura and chest wall produces chest
    pain, one of the commonest local symptoms in symptomatic thymic neuroendocrine
    carcinoma. No cohort quantifies its frequency, so no frequency band is
    asserted.
  phenotype_term:
    preferred_term: Chest pain
    term:
      id: HP:0100749
      label: Chest pain
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These patients were symptomatic with chest pain, shortness of breath, and
      dyspnea.
    explanation: >-
      Series of 24 thymic neuroendocrine carcinomas reporting chest pain among the
      presenting symptoms.
- category: Respiratory
  name: Dyspnea
  description: >-
    Compression or invasion of the airway, lung and great vessels by the
    mediastinal mass produces breathlessness. No cohort quantifies its frequency,
    so no frequency band is asserted.
  phenotype_term:
    preferred_term: Dyspnea
    term:
      id: HP:0002094
      label: Dyspnea
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These patients were symptomatic with chest pain, shortness of breath, and
      dyspnea.
    explanation: >-
      Series of 24 thymic neuroendocrine carcinomas reporting dyspnoea among the
      presenting symptoms.
- category: Respiratory
  name: Cough
  description: >-
    Airway irritation or compression by the prevascular mediastinal mass produces
    cough, alongside the chest pain and breathlessness reported as the presenting
    complaints of thymic neuroendocrine carcinoma. No thymic-NET frequency is
    published, so none is asserted.
  phenotype_term:
    preferred_term: Cough
    term:
      id: HP:0012735
      label: Cough
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These patients were symptomatic with chest pain, shortness of breath, and
      dyspnea.
    explanation: >-
      Establishes the respiratory mass-effect symptom complex in a series of 24
      thymic neuroendocrine carcinomas. Marked PARTIAL because the series lists
      chest pain and breathlessness but not cough specifically.
- category: Oncologic
  name: Mediastinal lymphadenopathy
  frequency: FREQUENT
  context: Locally advanced or metastatic disease
  description: >-
    Regional mediastinal nodal involvement is the commonest metastatic site,
    present in nearly three-quarters of advanced cases (the denominator on which
    the FREQUENT band is anchored); nodal positivity is a
    recognised adverse prognostic factor and drives the argument for systematic
    lymph node dissection at resection.
  phenotype_term:
    preferred_term: Mediastinal lymphadenopathy
    term:
      id: HP:0100721
      label: Mediastinal lymphadenopathy
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Metastatic sites were as follows: lymph nodes (54 patients, 73%)
    explanation: >-
      Directly supports lymph nodes as the commonest metastatic site (73% of
      advanced cases), consistent with the FREQUENT band.
- category: Skeletal
  name: Bone metastasis
  frequency: FREQUENT
  context: Locally advanced or metastatic disease
  description: >-
    Skeletal metastasis is characteristic of thymic neuroendocrine carcinoma,
    reported in 65% of a locally advanced / metastatic cohort and typically
    producing bone pain; bone involvement trends toward a worse prognosis. The
    FREQUENT band is anchored on that advanced-disease denominator, not on all
    incident cases.
  phenotype_term:
    preferred_term: Bone metastasis
    term:
      id: HP:0010622
      label: Neoplasm of the skeletal system
  notes: >-
    HPO has no "bone metastasis" class; HP:0010622 Neoplasm of the skeletal system
    is the closest available parent and is the term other dismech metastasis
    records use.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      bone (42 patients, 65%)
    explanation: >-
      Quantifies bone as a metastatic site in 65% of advanced thymic NET, supporting
      the FREQUENT band within that population.
- category: Oncologic
  name: Pulmonary metastasis
  frequency: FREQUENT
  context: Locally advanced or metastatic disease
  description: >-
    Haematogenous spread to the lung is a common metastatic site, reported in 42%
    of a locally advanced / metastatic thymic NET cohort and among the commonest
    sites in independent surgical series.
  phenotype_term:
    preferred_term: Pulmonary metastasis
    term:
      id: HP:0100526
      label: Neoplasm of the lung
  notes: >-
    HPO has no "pulmonary metastasis" class; HP:0100526 Neoplasm of the lung is
    the closest available parent and does not distinguish a metastatic deposit
    from a primary lung neoplasm. Same NTR-style caveat as the Bone metastasis
    and Pleural metastasis records.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      lung (31 patients, 42%), and pleura (31 patients, 42%)
    explanation: >-
      Quantifies pulmonary metastasis in 42% of advanced thymic NET.
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common sites of metastasis included lung, lymph node, brain, lumbar spine,
      mediastinum, bone, and liver.
    explanation: >-
      Independent surgical series listing lung among the common metastatic sites.
- category: Thoracic
  name: Pleural metastasis
  frequency: FREQUENT
  context: Locally advanced or metastatic disease
  description: >-
    Pleural involvement occurs in 42% of advanced thymic NET and is distinctive in
    being almost exclusively metachronous, raising the possibility of
    perioperative dissemination at the time of resection rather than intrinsic
    early tropism.
  notes: >-
    HPO has no pleural-neoplasm class; HP:0100606 Neoplasm of the respiratory
    system is the closest available parent (needs term / NTR candidate: neoplasm
    of the pleura). The preferred_term carries the intended specificity.
  phenotype_term:
    preferred_term: Pleural metastasis
    term:
      id: HP:0100606
      label: Neoplasm of the respiratory system
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Pleural metastases were almost exclusively metachronous.
    explanation: >-
      Documents the distinctive metachronous timing of pleural spread in advanced
      thymic NET.
- category: Gastrointestinal
  name: Hepatic metastasis
  context: Locally advanced or metastatic disease
  description: >-
    The liver is among the common sites of distant spread in thymic
    neuroendocrine carcinoma. No frequency band is asserted: the only
    thymic-NET-specific source is a qualitative list of common metastatic sites
    with no denominator, and the quantified French advanced-disease cohort does
    not separately report a hepatic figure.
  phenotype_term:
    preferred_term: Hepatic metastasis
    term:
      id: HP:0002896
      label: Neoplasm of the liver
  notes: >-
    HPO has no "hepatic metastasis" class; HP:0002896 Neoplasm of the liver is
    the closest available parent and does not distinguish a metastatic deposit
    from a primary hepatic neoplasm. Same NTR-style caveat as the Bone,
    Pulmonary and Pleural metastasis records.
  evidence:
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common sites of metastasis included lung, lymph node, brain, lumbar spine,
      mediastinum, bone, and liver.
    explanation: >-
      Surgical series listing the liver among the common metastatic sites in
      thymic neuroendocrine tumors.
- category: Neurological
  name: Cerebral metastasis
  context: Locally advanced or metastatic disease
  description: >-
    Brain metastasis is a recognised site of distant spread in thymic
    neuroendocrine carcinoma and is clinically consequential because it changes
    both surveillance imaging and systemic-therapy choice. No frequency band is
    asserted, for the same reason as hepatic metastasis: the source is a
    qualitative list of common sites without a denominator.
  phenotype_term:
    preferred_term: Cerebral metastasis
    term:
      id: HP:0030692
      label: Brain neoplasm
  notes: >-
    HP:0030692 Brain neoplasm is defined as "A benign or malignant neoplasm that
    arises from or metastasizes to the brain", so it does cover metastatic
    deposits, but it does not distinguish them from a primary brain neoplasm.
    The preferred_term carries the intended specificity.
  evidence:
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common sites of metastasis included lung, lymph node, brain, lumbar spine,
      mediastinum, bone, and liver.
    explanation: >-
      Surgical series listing the brain among the common metastatic sites in
      thymic neuroendocrine tumors.
- category: Constitutional
  name: Weight loss
  description: >-
    Constitutional weight loss occurs as a systemic manifestation of advanced or
    metastatic disease. No thymic-NET-specific frequency is published, so none is
    asserted.
  phenotype_term:
    preferred_term: Weight loss
    term:
      id: HP:0001824
      label: Weight loss
  evidence:
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Common sites of metastasis included lung, lymph node, brain, lumbar spine,
      mediastinum, bone, and liver.
    explanation: >-
      Documents the multi-organ metastatic burden that underlies constitutional
      weight loss. Marked PARTIAL because the series reports metastatic sites, not
      weight loss itself; no thymic-NET series quantifies constitutional symptoms.
histopathology:
- name: Neuroendocrine architecture with neuroendocrine marker expression
  finding_term:
    preferred_term: neuroendocrine differentiation on immunohistochemistry
    term:
      id: NCIT:C43574
      label: Neuroendocrine Differentiation
  frequency: OBLIGATE
  diagnostic: true
  description: >-
    Diagnosis requires neuroendocrine morphology (organoid nesting, trabeculae,
    rosettes; or sheets with high-grade cytology) together with
    immunohistochemical confirmation of neuroendocrine differentiation.
    Chromogranin A and synaptophysin are positive in the large majority of cases,
    and pancytokeratin positivity confirms the epithelial lineage that separates
    thymic neuroendocrine carcinoma from mediastinal paraganglioma.
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Chromogranin A and synaptophysin were expressed in 92% and 88% of cases,
      respectively, and TTF-1 in 4 (17%) of 24 cases.
    explanation: >-
      Quantifies neuroendocrine marker expression across 24 thymic neuroendocrine
      carcinomas.
- name: Mitotic count and necrosis grading
  finding_term:
    preferred_term: WHO neuroendocrine tumor grade (mitotic count and necrosis)
    term:
      id: NCIT:C177567
      label: WHO Neuroendocrine Tumor Grade
  diagnostic: true
  description: >-
    Grade is assigned from mitotic count per 2 mm2 and the presence of necrosis -
    typical carcinoid (low mitotic count, no necrosis), atypical carcinoid
    (intermediate mitotic count and/or punctate necrosis), and the poorly
    differentiated large cell neuroendocrine carcinoma and small cell carcinoma
    (high mitotic count, extensive necrosis). Mitotic count of 4 or more per 2 mm2
    and tumor size of 5 cm or more are associated with death of disease.
  evidence:
  - reference: PMID:33243039
    reference_title: "Typical and Atypical Carcinoid Tumors of the Mediastinum: A Biomarker Analysis of 27 Cases With Clinical Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Mitotic counts ≥4 per 2 mm2 and tumor size ≥5 cm, associated with death of
      disease (DoD; P = .010 and .016).
    explanation: >-
      Supports mitotic count and tumor size as histopathologic determinants of
      outcome in thymic carcinoid.
  - reference: PMID:35696052
    reference_title: "Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      another nodule with 25 mitoses per 2 mm2, qualifying for the 2021 WHO
      diagnosis of large cell neuroendocrine carcinoma (LCNEC)
    explanation: >-
      Illustrates the mitotic-count threshold that separates high-grade LCNEC from
      atypical carcinoid under the 2021 WHO scheme.
- name: Absent PD-L1 expression
  finding_term:
    preferred_term: lack of expression of PD-L1
    term:
      id: NCIT:C122809
      label: Lack of Expression of PD-L1
  description: >-
    In contrast to thymoma and thymic squamous cell carcinoma, which typically
    show a PD-L1-high phenotype, PD-L1 staining was absent in a series of 27
    thymic typical and atypical carcinoids. This is a mechanistic argument against
    reflexive extrapolation of checkpoint-inhibitor strategies from other thymic
    epithelial tumors to the neuroendocrine arm.
  evidence:
  - reference: PMID:33243039
    reference_title: "Typical and Atypical Carcinoid Tumors of the Mediastinum: A Biomarker Analysis of 27 Cases With Clinical Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Biomarkers stained tumor cases as follows: PDL-1 = 0%, PAX-5 = 0%, MET = 7.4%
    explanation: >-
      Directly supports absent PD-L1 staining across 27 mediastinal (thymic)
      carcinoids.
  - reference: PMID:34695605
    reference_title: "The 2021 WHO Classification of Tumors of the Thymus and Mediastinum: What Is New in Thymic Epithelial, Germ Cell, and Mesenchymal Tumors?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      thymomas and most thymic carcinomas lack currently targetable mutations, have
      an extraordinarily low tumor mutational burden, but typically have a
      programmed death-ligand 1high phenotype
    explanation: >-
      WHO classification overview establishing the PD-L1-high phenotype of thymoma
      and most thymic carcinomas, the contrast against which the PD-L1-negative
      neuroendocrine arm stands out. Evidence source is OTHER because this is a
      classification review.
biochemical:
- name: Chromogranin A expression
  biomarker_term:
    preferred_term: Chromogranin-A
    term:
      id: NCIT:C17284
      label: Chromogranin-A
  presence: present
  specificity: >-
    Sensitive marker of neuroendocrine differentiation in tissue; serum
    chromogranin A is non-specific and is not diagnostic on its own.
  notes: >-
    Immunohistochemical chromogranin A positivity is one of the two conventional
    neuroendocrine markers used to establish neuroendocrine differentiation in a
    thymic epithelial tumor.
  cell_types:
  - preferred_term: thymic neuroendocrine tumor cell
    term:
      id: CL:0000165
      label: neuroendocrine cell
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Chromogranin A and synaptophysin were expressed in 92% and 88% of cases,
      respectively
    explanation: >-
      Quantifies chromogranin A positivity in 92% of thymic neuroendocrine
      carcinomas.
- name: Synaptophysin expression
  biomarker_term:
    preferred_term: Synaptophysin
    term:
      id: NCIT:C101146
      label: Synaptophysin
  presence: present
  notes: >-
    The second conventional neuroendocrine marker; used alongside chromogranin A
    and pancytokeratin in the diagnostic immunohistochemical panel.
  cell_types:
  - preferred_term: thymic neuroendocrine tumor cell
    term:
      id: CL:0000165
      label: neuroendocrine cell
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Chromogranin A and synaptophysin were expressed in 92% and 88% of cases,
      respectively
    explanation: >-
      Quantifies synaptophysin positivity in 88% of thymic neuroendocrine
      carcinomas.
- name: Ki-67 proliferation index
  biomarker_term:
    preferred_term: Ki-67 Labeling Index
    term:
      id: NCIT:C157250
      label: Ki-67 Labeling Index
  presence: present
  notes: >-
    Ki-67 labeling index quantifies proliferative activity and is used alongside
    mitotic count for grading. In thymic carcinoid even a low Ki-67 threshold has
    prognostic weight.
  evidence:
  - reference: PMID:33243039
    reference_title: "Typical and Atypical Carcinoid Tumors of the Mediastinum: A Biomarker Analysis of 27 Cases With Clinical Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Ki-67 expression ≥1% associated with DoD (P = .003) and death within 5 years
      (P = .031).
    explanation: >-
      Supports Ki-67 labeling index as a prognostic biomarker in thymic carcinoid.
- name: Plasma adrenocorticotropic hormone
  biomarker_term:
    preferred_term: Adrenocorticotropic Hormone Measurement
    term:
      id: NCIT:C74780
      label: Adrenocorticotropic Hormone Measurement
  presence: elevated
  context: Ectopic Cushing syndrome subset
  notes: >-
    In the functional subset, plasma ACTH is inappropriately normal or elevated in
    the face of hypercortisolism (ACTH-dependent Cushing syndrome). Localising the
    source to an ectopic thymic tumor rather than a pituitary corticotroph adenoma
    requires dynamic testing (high-dose dexamethasone suppression, CRH stimulation,
    inferior petrosal sinus sampling) plus cross-sectional and
    somatostatin-receptor imaging of the mediastinum. No thymic-NET-specific
    reference interval exists, so none is curated.
  evidence:
  - reference: PMID:30502716
    reference_title: "Carcinoid tumors of the thymus and Cushing's syndrome: Clinicopathologic features and current best evidence regarding the cell of origin of these unusual neoplasms."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thymic NET with CS exhibited stronger immunoreactivity for ACTH and CRH than
      those without CS.
    explanation: >-
      Supports tumoral ACTH production as the source of the ACTH-dependent
      syndrome. Marked PARTIAL because the study measures tumor immunoreactivity
      rather than plasma ACTH concentration.
  - reference: PMID:35690804
    reference_title: "Successful resolution of ectopic Cushing syndrome by minimally invasive thoracoscopic resection of the neuroendocrine tumor of the thymus: a rare case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The levels of the hormones ACTH, aldosterone, and renin were determined to be
      281 pg/mL, 3.0 ng/dL, and 2.1 pg/mL, respectively.
    explanation: >-
      Reports the markedly elevated plasma ACTH concentration in a patient with a
      thymic carcinoid causing ectopic ACTH-dependent Cushing syndrome.
- name: Serum cortisol
  biomarker_term:
    preferred_term: Cortisol Measurement
    term:
      id: NCIT:C74781
      label: Cortisol Measurement
  presence: elevated
  context: Ectopic Cushing syndrome subset
  notes: >-
    Hypercortisolism is confirmed biochemically before localisation (elevated
    late-night salivary cortisol, elevated 24-hour urinary free cortisol, failure of
    low-dose dexamethasone suppression). Reference intervals are deliberately not
    curated here because cortisol assays are strongly method- and
    time-of-day-dependent and no thymic-NET-specific interval exists.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      11 patients (15%) with ectopic Cushing syndrome
    explanation: >-
      Establishes the clinical hypercortisolism syndrome in 15% of advanced thymic
      NET. Marked PARTIAL because the cohort reports the syndrome rather than
      cortisol concentrations.
  - reference: PMID:35690804
    reference_title: "Successful resolution of ectopic Cushing syndrome by minimally invasive thoracoscopic resection of the neuroendocrine tumor of the thymus: a rare case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cortisol levels increased in the morning, reaching 47.7 ug/dL.
    explanation: >-
      Reports the elevated morning serum cortisol in a thymic carcinoid causing
      ectopic ACTH-dependent Cushing syndrome.
- name: Somatostatin receptor 2 expression
  biomarker_term:
    preferred_term: Somatostatin Receptor Type 2
    term:
      id: NCIT:C17922
      label: Somatostatin Receptor Type 2
  presence: variable
  specificity: >-
    Predictive rather than diagnostic - membranous SSTR2 expression determines
    DOTATATE imaging avidity and eligibility for somatostatin-analogue therapy and
    peptide receptor radionuclide therapy.
  notes: >-
    Expression is present in a minority-to-majority of thymic epithelial tumors
    depending on histology, and high-level expression associates with shorter
    recurrence/metastasis-free survival.
  evidence:
  - reference: PMID:35198446
    reference_title: "Correlation of Somatostatin Receptor 2 Expression, 68Ga-DOTATATE PET Scan and Octreotide Treatment in Thymic Epithelial Tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      SSTR2 expression was identified in 29 (of 80, 36.3%) TET including 2/2 (100%)
      small cell carcinomas, 2/5 (40.0%) atypical carcinoid tumors
    explanation: >-
      Quantifies SSTR2 expression across thymic epithelial tumor histologies
      including the neuroendocrine subtypes.
environmental:
- name: Tobacco smoking
  presence: risk factor
  exposure_term:
    preferred_term: exposure to tobacco smoking
    term:
      id: ECTO:6000029
      label: exposure to tobacco smoking
  description: >-
    Smoking is the only environmental exposure with an asserted link to carcinoid
    risk in the MEN1 setting, and it is the stated basis for targeting prophylactic
    thymectomy at male smokers. The association is not firmly quantified for thymic
    neuroendocrine carcinoma specifically, and it is contested: a referral-centre
    MEN1 thymic-carcinoid series found that two thirds of its patients were
    non-smokers. It is therefore curated as a probable but unsettled risk factor,
    and it is a plausible partial confounder of the male predominance recorded in
    the epidemiology section rather than a proven one.
  effect: Increased risk of carcinoid tumor development
  evidence:
  - reference: PMID:20301710
    reference_title: "Multiple Endocrine Neoplasia Type 1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Smoking increases the risk of carcinoid tumors.
    explanation: >-
      GeneReviews Agents/Circumstances to Avoid guidance for MEN1 names smoking as a
      carcinoid risk factor. Evidence source is OTHER because GeneReviews is an
      expert-curated review.
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The few published reports associate these tumors with male sex and smoking.
    explanation: >-
      Records the historical male-sex-and-smoking association. Marked PARTIAL because
      the same paper immediately qualifies it (see the refuting item below).
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Six patients were non-smokers (67 %).
    explanation: >-
      In a 9-patient MEN1 thymic-carcinoid series two thirds of patients were
      non-smokers, arguing against smoking as a necessary or dominant risk factor
      and against using smoking status to gate surveillance.
genetic:
- name: MEN1 (germline)
  gene_term:
    preferred_term: MEN1
    term:
      id: hgnc:7010
      label: MEN1
  relationship_type: CAUSATIVE
  variant_origin: GERMLINE
  association: >-
    Germline loss-of-function variants in MEN1 cause multiple endocrine neoplasia
    type 1, in which thymic neuroendocrine tumors are an uncommon but
    disproportionately lethal manifestation. Thymic carcinoids occur in 1-5% of
    MEN1 patients; conversely a quarter to a third of thymic neuroendocrine
    neoplasms arise on a MEN1 background.
  features: >-
    Both truncating point variants and whole-exon copy-number variants are
    represented; no thymic-specific genotype-phenotype correlation has been
    established.
  case_fractions:
  - population: French national advanced thymic NET cohort (GTE / ENDOCAN RENATEN / RYTHMIC)
    case_fraction_percent: 34.0
    cohort_size: 74
    notes: >-
      Proportion of patients with locally advanced or metastatic thymic NET who
      carried the MEN1 inherited syndrome.
    evidence:
    - reference: PMID:40328381
      reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        multiple endocrine neoplasia type 1 inherited syndrome in 25 patients (34%)
      explanation: >-
        Directly quantifies the MEN1 share of an advanced thymic NET cohort.
  inheritance:
  - name: MEN1 autosomal dominant predisposition
    inheritance_term:
      preferred_term: Autosomal dominant inheritance
      term:
        id: HP:0000006
        label: Autosomal dominant inheritance
    description: >-
      MEN1 syndrome is inherited in an autosomal dominant manner; the thymic tumor
      itself arises after somatic loss of the second allele.
  evidence:
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thymic carcinoids are rare neuroendocrine tumors that occur in 1-5 % of
      patients with multiple endocrine neoplasia type 1 (MEN1) and are a major
      cause of morbidity and mortality.
    explanation: >-
      Establishes the MEN1-thymic carcinoid association and its mortality impact.
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Five patients had MEN1 genetic testing, and the genotypes of affected
      individuals were p.W341X, c.275_286delGCTTCACCGCCC, p.R98X,
      c.1350+(1_11)del11, and partial duplication of exons 9 and 10.
    explanation: >-
      Documents the germline MEN1 variant spectrum in patients with thymic
      carcinoid, spanning nonsense, frameshift, splice and copy-number variants.
  - reference: PMID:20301710
    reference_title: "Multiple Endocrine Neoplasia Type 1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The molecular diagnosis can be established by identification of a
      heterozygous pathogenic variant in MEN1 on molecular genetic testing.
    explanation: >-
      GeneReviews establishes germline MEN1 testing as the molecular basis of MEN1
      diagnosis, the predisposition context for thymic neuroendocrine tumors.
      Evidence source is OTHER because GeneReviews is an expert-curated review.
- name: MEN1 (somatic)
  gene_term:
    preferred_term: MEN1
    term:
      id: hgnc:7010
      label: MEN1
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  association: >-
    MEN1 is also the most frequently somatically altered gene in thymic
    neuroendocrine neoplasms in tumor panel sequencing, including in patients
    without a clinical MEN1 syndrome.
  notes: >-
    A tumor-only MEN1 alteration does not by itself establish hereditary MEN1;
    germline confirmation is required before cascade testing.
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those in TNENs were in MEN1, MLL2, APC, RB1
    explanation: >-
      324-gene panel sequencing of 15 thymic neuroendocrine neoplasms ranks MEN1
      first among clinically relevant genomic alterations.
- name: RB1
  gene_term:
    preferred_term: RB1
    term:
      id: hgnc:9884
      label: RB1
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  association: >-
    RB1 is among the top-ranked somatically altered genes in thymic neuroendocrine
    neoplasms, consistent with RB-axis checkpoint loss as a driver of the
    higher-grade end of the spectrum.
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those in TNENs were in MEN1, MLL2, APC, RB1
    explanation: >-
      Ranks RB1 among the most frequently altered genes in thymic neuroendocrine
      neoplasms.
- name: KMT2D
  gene_term:
    preferred_term: KMT2D
    term:
      id: hgnc:7133
      label: KMT2D
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  association: >-
    MLL2 (KMT2D), a histone H3K4 methyltransferase, is recurrently altered in
    thymic neuroendocrine neoplasms - a chromatin-remodelling lesion that is
    mechanistically congruent with the chromatin-adaptor function of menin.
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      those in TNENs were in MEN1, MLL2, APC, RB1
    explanation: >-
      Ranks MLL2 (KMT2D) among the most frequently altered genes in thymic
      neuroendocrine neoplasms.
- name: ERBB2
  gene_term:
    preferred_term: ERBB2
    term:
      id: hgnc:3430
      label: ERBB2
  relationship_type: BIOMARKER
  variant_origin: SOMATIC
  association: >-
    Somatic ERBB2 mutation was associated with shortened disease-free and overall
    survival specifically in thymic neuroendocrine neoplasm patients, marking it as
    a candidate prognostic (and potentially actionable) alteration.
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      mutation of ERBB2 indicated shortened disease-free survival (DFS) and overall
      survival (OS) in TNEN patients
    explanation: >-
      Directly supports ERBB2 mutation as an adverse prognostic marker in thymic
      neuroendocrine neoplasms.
inheritance:
- name: Sporadic with an autosomal dominant MEN1 subset
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Most thymic neuroendocrine carcinoma is sporadic. The heritable fraction is
    accounted for by autosomal dominant multiple endocrine neoplasia type 1
    (germline MEN1), which underlies roughly a quarter to a third of cases.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      multiple endocrine neoplasia type 1 inherited syndrome in 25 patients (34%)
    explanation: >-
      Quantifies the inherited (MEN1) fraction of an advanced thymic NET cohort.
  - reference: PMID:20301710
    reference_title: "Multiple Endocrine Neoplasia Type 1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Each child (regardless of sex) of an individual with MEN1 has a 50% chance of
      inheriting the pathogenic variant.
    explanation: >-
      GeneReviews gives the autosomal dominant transmission risk that governs cascade
      testing of relatives. Evidence source is OTHER because GeneReviews is an
      expert-curated review.
prevalence:
- population: Patients with multiple endocrine neoplasia type 1 (tertiary referral centre)
  measure_type: LIFETIME_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 3000.0
  rate_low: 1000.0
  rate_high: 5000.0
  notes: >-
    1-5% of MEN1 patients develop a thymic carcinoid; converted to 1000-5000 per
    100,000 of the MEN1 population. This is a within-syndrome risk, not a
    general-population rate.
  evidence:
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thymic carcinoids are rare neuroendocrine tumors that occur in 1-5 % of
      patients with multiple endocrine neoplasia type 1 (MEN1)
    explanation: >-
      Source for the 1-5% within-MEN1 lifetime occurrence figure.
- population: Finnish MEN1 patients (three university hospitals, 1985-2019)
  measure_type: LIFETIME_PREVALENCE
  prevalence_class: ABOVE_1_IN_1000
  rate_per_100000: 3300.0
  notes: >-
    6 of 183 MEN1 patients (3.3%) developed a thymic neuroendocrine tumor;
    converted to 3300 per 100,000 of the MEN1 population. Numerically consistent
    with the 1-5% referral-centre estimate, but NOT an independent confirmation of
    it: five of the six affected patients shared one Finnish founder MEN1 variant
    and descended from a single pedigree, so the rate is inflated by relatedness
    and is not generalisable.
  evidence:
  - reference: PMID:35696052
    reference_title: "Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      There were six patients (3.3%) with MEN1 and TNET.
    explanation: >-
      Population-based Finnish MEN1 cohort quantifying the within-syndrome
      occurrence of thymic neuroendocrine tumor.
  - reference: PMID:35696052
    reference_title: "Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Five of them had the same common gene mutation occurring in Finland. They
      originated from common ancestors encompassing two pairs of brothers from
      sequential generations.
    explanation: >-
      Establishes that five of the six cases derive from one founder pedigree, which
      is why this 3.3% figure must not be treated as an independent population
      estimate. Marked PARTIAL because it qualifies rather than supports the rate.
- population: Worldwide (general population)
  measure_type: POINT_PREVALENCE
  prevalence_class: ULTRA_RARE
  notes: >-
    No reliable general-population incidence or prevalence rate for thymic
    neuroendocrine carcinoma alone was identified. Registry analyses report thymic
    "cancer" incidence per 100,000 without breaking out the neuroendocrine arm, and
    the largest dedicated series accrue only tens to low hundreds of patients over
    multi-decade windows. Orphanet lists no prevalence class for ORPHA:99869. The
    numeric slots are therefore deliberately left empty rather than fabricated.
  evidence:
  - reference: PMID:40068632
    reference_title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
    supports: PARTIAL
    evidence_source: OTHER
    snippet: >-
      Thymic carcinoids or neuroendocrine neoplasms (t-NEN) are a rare entity with
      a dismal prognosis.
    explanation: >-
      Supports the qualitative rarity band only; the review provides no numeric
      population rate. Evidence source is OTHER because this is a narrative review.
epidemiology:
- name: Male predominance
  description: >-
    Thymic neuroendocrine carcinoma shows a consistent and marked male predominance
    across independent series and registries - approximately 2.7:1 in a French
    national advanced-disease cohort, 25:5 in a Japanese multicentre surgical
    series, 15:6 in a Korean surgical series, and 20:4 in a US immunohistochemical
    series. The excess appears less pronounced in MEN1-associated disease, where
    the underlying autosomal dominant predisposition is sex-neutral.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Main characteristics were as follows: male over female ratio of 2.7
    explanation: >-
      Directly quantifies the male:female ratio in a 74-patient national cohort.
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It showed male predominance (male/female ratio, 15/6) with wide age range
      from 20 to 72 years (mean age, 49 years).
    explanation: >-
      Independent surgical series confirming male predominance and giving the age
      distribution.
  - reference: PMID:20485130
    reference_title: "Thymic neuroendocrine tumors: a SEER database analysis of 160 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      According to our results, thymic NETs afflict males and whites primarily.
    explanation: >-
      Population-based SEER analysis of 160 patients confirming male predominance.
  - reference: PMID:29049806
    reference_title: "Results of treatment for thymic neuroendocrine tumours: multicentre clinicopathological study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Thirty patients (25 men and 5 women)
    explanation: >-
      Japanese multicentre surgical series with a 5:1 male:female ratio.
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A higher percentage of MEN1-related thymic carcinoids can occur in women and
      in non-smokers than previously reported.
    explanation: >-
      Supports the qualifier that the male excess is attenuated in MEN1-associated
      disease. Marked PARTIAL because the cohort is small (9 patients).
- name: Elevated second-malignancy risk
  description: >-
    Patients with thymic neuroendocrine tumor carry a significantly increased risk
    of a second primary malignancy relative to the general population - an
    age-adjusted second-cancer incidence of 4178.46 per 100,000 persons in the SEER
    thymic NET cohort (19 of 263 patients from 2000-2018), higher than the
    corresponding figure for thymic carcinoma. Age at diagnosis is a significant
    risk factor, and the risk is not attributable to any particular treatment
    modality. This is the epidemiological basis for extending follow-up beyond
    recurrence surveillance to include age-appropriate second-cancer screening.
  evidence:
  - reference: PMID:38227201
    reference_title: "Incidence of second malignancies in patients with thymic carcinoma and thymic neuroendocrine tumor."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      1130 patients with thymic carcinoma (73 patients had second malignancies) and
      263 patients with thymic NET (19 patients had second malignancies) from 2000
      to 2018 are included.
    explanation: >-
      Gives the SEER thymic NET denominator and the number developing a second
      malignancy.
  - reference: PMID:38227201
    reference_title: "Incidence of second malignancies in patients with thymic carcinoma and thymic neuroendocrine tumor."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The age-adjusted cancer incidence of second malignancies in patients with
      thymic carcinoma is 3058.48 per 100,000 persons (4178.46 per 100,000 persons
      in patients with thymic NET). Age at diagnosis is a significant risk factor
      for the development of second malignancies.
    explanation: >-
      Quantifies the age-adjusted second-cancer incidence in thymic NET and
      identifies age at diagnosis as a risk factor.
  - reference: PMID:38227201
    reference_title: "Incidence of second malignancies in patients with thymic carcinoma and thymic neuroendocrine tumor."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The standardized incidence ratio (SIR) and the age-adjusted cancer incidence
      of the thymic carcinoma and thymic NET patients with second malignancies were
      retrospectively calculated by using the Surveillance, Epidemiology, and End
      Results (SEER) database.
    explanation: >-
      Establishes the SEER standardized-incidence-ratio methodology behind the
      second-malignancy risk estimate.
  - reference: PMID:38227201
    reference_title: "Incidence of second malignancies in patients with thymic carcinoma and thymic neuroendocrine tumor."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The incidence of second malignancies in patients with thymic carcinoma and
      thymic NET is significantly higher than the patients in the normal
      population. The occurrence of second malignancies is not related to the use
      of different treatments.
    explanation: >-
      Supports both the elevated second-malignancy risk and the finding that it is
      not treatment-attributable.
- name: Adult onset with a wide age range
  description: >-
    Presentation is in adulthood, typically in the fourth to fifth decade, with a
    wide reported age range (roughly 20 to 78 years). MEN1-associated cases tend to
    present somewhat earlier than sporadic disease.
  evidence:
  - reference: PMID:23110006
    reference_title: "Clinicopathological analysis of 21 thymic neuroendocrine tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      wide age range from 20 to 72 years (mean age, 49 years)
    explanation: >-
      Gives the age distribution of a thymic neuroendocrine tumor surgical series.
  - reference: PMID:35696052
    reference_title: "Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The mean age at presentation of TNET was 44.7 ± 11.9 years.
    explanation: >-
      Gives mean age at presentation in the MEN1-associated subset.
progression:
- age_range: adulthood
  notes: >-
    Behaviour is graded. Reported 5- and 10-year overall survival in surgical
    series is 77% and 35% (Japanese multicentre, all grades) and 53% and 18% (a
    mediastinal typical/atypical carcinoid biomarker series). In a modern French
    national cohort restricted to locally advanced or metastatic disease the 5-year
    overall survival was 85%, better than historically reported. Prognosis is
    markedly worse for the poorly differentiated grades - in one series all 3
    patients with large cell neuroendocrine carcinoma died of tumor progression
    versus 17% of atypical carcinoid patients. MEN1-associated disease is
    aggressive, with 5- and 10-year survival of 62.5% and 31.3% in a Finnish cohort
    and 10-year overall survival of 45% at a US referral centre. Late metachronous
    recurrence is characteristic, so surveillance must be prolonged.
  evidence:
  - reference: PMID:29049806
    reference_title: "Results of treatment for thymic neuroendocrine tumours: multicentre clinicopathological study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Overall survival was 77% after 5 years and 35% after 10 years, whereas
      relapse-free survival was 48% and 29%, and cancer-specific survival was 90%
      and 48%, respectively.
    explanation: >-
      Provides multicentre 5- and 10-year survival for resected thymic
      neuroendocrine tumors.
  - reference: PMID:33243039
    reference_title: "Typical and Atypical Carcinoid Tumors of the Mediastinum: A Biomarker Analysis of 27 Cases With Clinical Correlation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Five- and 10-year-survival rates were 53% and 18%, respectively.
    explanation: >-
      Independent survival estimate for mediastinal typical/atypical carcinoid.
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The 5-year overall survival was 85%.
    explanation: >-
      Contemporary survival estimate in advanced disease, better than historical
      series.
  - reference: PMID:35696052
    reference_title: "Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In our patients, the 5-year survival of the TNET patients was 62.5% and
      10-year survival 31.3%.
    explanation: >-
      Survival in the MEN1-associated subset.
  - reference: PMID:27311764
    reference_title: "Clinical Features, Treatments, and Outcomes of Patients with Thymic Carcinoids and Multiple Endocrine Neoplasia Type 1 Syndrome at MD Anderson Cancer Center."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The 10-year overall survival rate was 45 %
    explanation: >-
      Referral-centre 10-year overall survival in MEN1-associated thymic carcinoid.
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Univariate analysis on overall survival reveals a trend toward worse prognosis
      in case of female gender and bone metastases and better prognosis for patients
      with multiple endocrine neoplasia type 1.
    explanation: >-
      Counterweight to the historical framing of MEN1-associated thymic disease as
      uniformly more aggressive: in the largest modern advanced-disease cohort MEN1
      status trended toward BETTER overall survival, plausibly reflecting earlier
      detection through syndrome surveillance. Marked PARTIAL because this is an
      unadjusted univariate trend, not a confirmed prognostic effect.
diagnosis:
- name: Contrast-enhanced chest CT
  description: >-
    Cross-sectional imaging of the chest is the primary anatomical study, defining
    the prevascular mediastinal mass, its relationship to great vessels and
    pericardium, and nodal involvement. MRI adds value for vascular, cardiac or
    spinal invasion.
- name: Somatostatin receptor PET/CT (68Ga-DOTATATE) and 18F-FDG PET/CT
  description: >-
    Functional somatostatin-receptor imaging is positive in about three-quarters of
    advanced thymic NET and is used both for staging and to select patients for
    somatostatin-analogue therapy or peptide receptor radionuclide therapy. 18F-FDG
    PET is complementary and is positive in a higher fraction, reflecting the
    proliferative high-grade component.
  evidence:
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Positive results for 18F-FDG or somatostain receptor imaging was found in 88%
      or 74% of cases, respectively.
    explanation: >-
      Quantifies the diagnostic yield of both functional imaging modalities in
      advanced thymic NET.
- name: Histopathology with neuroendocrine immunohistochemical panel
  description: >-
    Tissue diagnosis is mandatory. The panel comprises pancytokeratin (epithelial
    lineage), chromogranin A and synaptophysin (neuroendocrine differentiation) and
    Ki-67 (proliferation); GATA-3 and TTF-1 help exclude paraganglioma and
    pulmonary origin respectively. Mitotic count per 2 mm2 and necrosis assign
    grade.
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      we recommend that the workup of neuroendocrine tumors should include not only
      the conventional neuroendocrine markers and pancytokeratin but also other
      markers such as GATA-3 and TTF-1 in order to arrive at a better
      interpretation.
    explanation: >-
      Directly recommends the immunohistochemical panel used to diagnose thymic
      neuroendocrine carcinoma and exclude its mimics.
- name: Germline MEN1 testing and endocrine syndrome screening
  description: >-
    Because a quarter to a third of cases are MEN1-associated, a new diagnosis of
    thymic neuroendocrine carcinoma should prompt germline MEN1 sequencing with
    deletion/duplication analysis plus biochemical screening for
    hyperparathyroidism and pituitary and gastroenteropancreatic tumors -
    especially in younger patients, those with other endocrine tumors, or those
    with a suggestive family history.
  evidence:
  - reference: PMID:20301710
    reference_title: "Multiple Endocrine Neoplasia Type 1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The molecular diagnosis can be established by identification of a
      heterozygous pathogenic variant in MEN1 on molecular genetic testing.
    explanation: >-
      GeneReviews basis for germline MEN1 testing. Evidence source is OTHER because
      GeneReviews is an expert-curated review.
differential_diagnoses:
- name: Thymoma
  disease_term:
    preferred_term: thymoma
    term:
      id: MONDO:0006456
      label: thymoma
  description: >-
    The other major thymic epithelial tumor family and the principal
    anterior-mediastinal differential. Curated separately in
    kb/disorders/Thymoma.yaml; deliberately not duplicated here.
  distinguishing_features:
  - >-
    Thymoma is organotypic and contains immature TdT-positive thymocytes; thymic
    neuroendocrine carcinoma does not.
  - >-
    Thymoma carries the classic autoimmune paraneoplastic syndromes (myasthenia
    gravis, pure red cell aplasia, Good syndrome); thymic neuroendocrine carcinoma
    instead carries the ectopic ACTH/Cushing endocrine syndrome.
  - >-
    Thymoma lacks chromogranin A / synaptophysin neuroendocrine marker expression.
  - >-
    Thymoma typically shows a PD-L1-high phenotype, whereas PD-L1 staining was
    absent across a series of thymic carcinoids.
  evidence:
  - reference: PMID:34695605
    reference_title: "The 2021 WHO Classification of Tumors of the Thymus and Mediastinum: What Is New in Thymic Epithelial, Germ Cell, and Mesenchymal Tumors?"
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      thymomas and most thymic carcinomas lack currently targetable mutations, have
      an extraordinarily low tumor mutational burden, but typically have a
      programmed death-ligand 1high phenotype
    explanation: >-
      Establishes the PD-L1-high phenotype of thymoma, which distinguishes it from
      the PD-L1-negative thymic carcinoid. Evidence source is OTHER because this is
      a classification review.
- name: Thymic carcinoma (non-neuroendocrine)
  disease_term:
    preferred_term: thymic carcinoma
    term:
      id: MONDO:0006451
      label: thymic carcinoma
  description: >-
    Overtly malignant, non-organotypic thymic epithelial carcinoma, predominantly
    squamous cell type. Curated separately in kb/disorders/Thymic_Carcinoma.yaml;
    deliberately not duplicated here. Note that MONDO places thymic neuroendocrine
    carcinoma beneath thymic carcinoma, so this is a parent entity as well as a
    practical differential.
  distinguishing_features:
  - >-
    Thymic squamous cell carcinoma characteristically coexpresses CD5 and CD117
    (KIT). CD5 is not a feature of the neuroendocrine arm; CD117/KIT is less
    discriminating, since a proportion of neuroendocrine tumors are also
    KIT-positive, so this marker pair should not be used alone.
  - >-
    Genomics differ - conventional thymic carcinoma is dominated by CDKN2A, TP53,
    ASXL1 and CDKN2B alterations, whereas thymic neuroendocrine neoplasms are
    dominated by MEN1, MLL2, APC, RB1 and TSC2.
  - >-
    Neuroendocrine marker expression (chromogranin A, synaptophysin) is required
    for the neuroendocrine designation.
  evidence:
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The mutational profiles between TCs and TNENs were diverse.
    explanation: >-
      Panel sequencing establishing that thymic carcinoma and thymic neuroendocrine
      neoplasms have distinct mutational profiles, supporting their separation as
      entities.
  - reference: PMID:37749819
    reference_title: "Genetic insights into thymic carcinomas and thymic neuroendocrine neoplasms denote prognosis signatures and pathways."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The genetic alterations that ranked highest in TCs were in CDKN2A, TP53,
      ASXL1, CDKN2B, PIK3C2G, PTCH1, and ROS1
    explanation: >-
      Gives the thymic carcinoma gene ranking that contrasts with the
      MEN1/MLL2/APC/RB1 ranking of thymic neuroendocrine neoplasms.
- name: Mediastinal paraganglioma
  disease_term:
    preferred_term: paraganglioma
    term:
      id: MONDO:0000448
      label: paraganglioma
  description: >-
    A neuroendocrine mediastinal neoplasm that mimics thymic carcinoid
    morphologically but is of neural crest rather than epithelial origin.
  distinguishing_features:
  - >-
    Paraganglioma is pancytokeratin-negative and frequently GATA-3-positive;
    thymic neuroendocrine carcinoma is universally pancytokeratin-positive and
    GATA-3-negative.
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All paragangliomas were universally positive for chromogranin A and
      synaptophysin, but negative for pancytokeratin, TTF-1, and napsin A. GATA-3
      was expressed in 12 (55%) of 22 tumors.
    explanation: >-
      Directly supports the pancytokeratin/GATA-3 immunophenotype that separates
      paraganglioma from thymic neuroendocrine carcinoma.
- name: Metastatic or directly invading pulmonary neuroendocrine carcinoma
  disease_term:
    preferred_term: lung neuroendocrine neoplasm
    term:
      id: MONDO:0005454
      label: lung neuroendocrine neoplasm
  description: >-
    Small cell and large cell neuroendocrine carcinoma of the lung can involve the
    anterior mediastinum by direct extension or nodal metastasis, and is far
    commoner than a primary thymic neuroendocrine carcinoma.
  distinguishing_features:
  - >-
    TTF-1 positivity favours a pulmonary primary; only a minority (about 17%) of
    thymic neuroendocrine carcinomas are TTF-1 positive.
  - >-
    Radiological demonstration of a dominant pulmonary lesion, and absence of a
    thymus-centred prevascular mass, favours pulmonary origin.
  evidence:
  - reference: PMID:25294372
    reference_title: "Thymic neuroendocrine tumors (paraganglioma and carcinoid tumors): a comparative immunohistochemical study of 46 cases."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      TTF-1 in 4 (17%) of 24 cases
    explanation: >-
      Quantifies TTF-1 positivity in thymic neuroendocrine carcinoma, which limits
      but does not eliminate TTF-1 as a discriminator from pulmonary primaries.
treatments:
- name: Complete surgical resection (thymectomy)
  therapeutic_modality: SURGERY
  action_category: THERAPEUTIC
  target_mechanisms:
  - target: Mediastinal Mass Effect and Local Invasion
    treatment_effect: INHIBITS
    description: >-
      En-bloc resection removes the primary tumor and its locally invasive front,
      the only intervention that can interrupt the pathograph at its anatomical
      source.
  description: >-
    Macroscopically complete en-bloc resection of the thymus and tumor, with
    resection of involved adjacent structures and systematic mediastinal lymph node
    dissection, is the mainstay of treatment and the only potentially curative
    modality. Complete resection is associated with significantly better overall
    survival.
  treatment_term:
    preferred_term: Thymectomy
    term:
      id: NCIT:C29894
      label: Thymectomy
  evidence:
  - reference: PMID:29049806
    reference_title: "Results of treatment for thymic neuroendocrine tumours: multicentre clinicopathological study."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Overall survival was significantly better in patients who underwent
      macroscopic complete resection (P = 0.010).
    explanation: >-
      Multicentre surgical series supporting complete resection as the key
      determinant of survival.
  - reference: PMID:40068632
    reference_title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      The mainstay of therapy is surgical resection as it is associated with
      significantly improved long-term survival.
    explanation: >-
      Review confirming surgery as the mainstay of therapy. Evidence source is
      OTHER because this is a narrative review.
- name: Adjuvant radiotherapy after resection
  therapeutic_modality: RADIOTHERAPY
  action_category: THERAPEUTIC
  description: >-
    Postoperative radiotherapy is used selectively for incomplete margins or
    locally advanced disease. The evidence is mixed and weak - in a multicentre
    surgical series receipt of adjuvant therapy was associated with better
    relapse-free survival, but a SEER analysis of 160 patients found no survival
    benefit for radiation delivered as part of primary therapy. Both sides of the
    evidence are curated here so the uncertainty is explicit.
  treatment_term:
    preferred_term: Radiation Therapy
    term:
      id: NCIT:C15313
      label: Radiation Therapy
  evidence:
  - reference: PMID:29049806
    reference_title: "Results of treatment for thymic neuroendocrine tumours: multicentre clinicopathological study."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      As for relapse-free survival patients, TNM Stage I or II (P = 0.011) and
      received adjuvant therapy patients (P = 0.042) showed good survival rates.
    explanation: >-
      Supports a relapse-free survival association with adjuvant therapy. Marked
      PARTIAL because this is an unadjusted association in a small retrospective
      series and covers adjuvant therapy generally rather than radiotherapy
      specifically.
  - reference: PMID:20485130
    reference_title: "Thymic neuroendocrine tumors: a SEER database analysis of 160 patients."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We did not observe any survival benefit for radiation delivered as a part of
      primary therapy.
    explanation: >-
      SEER analysis finding no survival benefit for primary radiotherapy, the
      counterweight to the single-series adjuvant association above.
- name: Platinum-etoposide chemotherapy
  therapeutic_modality: SMALL_MOLECULE
  action_category: THERAPEUTIC
  target_mechanisms:
  - target: Neuroendocrine Clonal Expansion in the Thymus
    treatment_effect: INHIBITS
    description: >-
      Platinum DNA crosslinking plus topoisomerase II poisoning kills the rapidly
      cycling high-grade neuroendocrine clone, which is why response is best in the
      most proliferative (small cell and large cell) grades.
  description: >-
    For poorly differentiated (small cell and large cell) thymic neuroendocrine
    carcinoma, platinum plus etoposide is the preferred systemic regimen, adopted
    by extrapolation from pulmonary and extrapulmonary high-grade neuroendocrine
    carcinoma. In the French advanced-disease cohort, partial responses were seen
    most often with cytotoxic chemotherapy. No thymus-specific randomised
    comparison exists.
  treatment_term:
    preferred_term: Chemotherapy
    term:
      id: NCIT:C15632
      label: Chemotherapy
    therapeutic_agent:
    - preferred_term: cisplatin
      term:
        id: CHEBI:27899
        label: cisplatin
    - preferred_term: carboplatin
      term:
        id: CHEBI:31355
        label: carboplatin
    - preferred_term: etoposide
      term:
        id: CHEBI:4911
        label: etoposide
  evidence:
  - reference: PMID:40068632
    reference_title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      for non-resectable and recurring disease, platinum-based chemotherapies are
      preferred in neuroendocrine carcinoma, while everolimus and temozolomide are
      recommended in thymic neuroendocrine tumors.
    explanation: >-
      Review recommending platinum-based chemotherapy for the neuroendocrine
      carcinoma (high-grade) arm. Evidence source is OTHER because this is a
      narrative review.
  - reference: PMID:40328381
    reference_title: "Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Partial responses were more frequently observed in patients treated with
      cytotoxic chemotherapy.
    explanation: >-
      National-network cohort reporting cytotoxic chemotherapy as the modality most
      often producing partial responses in advanced thymic NET.
- name: Everolimus
  therapeutic_modality: SMALL_MOLECULE
  action_category: THERAPEUTIC
  target_mechanisms:
  - target: mTOR Pathway Restraint Loss
    treatment_effect: INHIBITS
    description: >-
      Everolimus inhibits mTORC1, restoring the growth-signalling restraint lost
      when TSC2 (tuberin) is inactivated.
  description: >-
    The mTOR inhibitor everolimus is recommended for well-differentiated thymic
    neuroendocrine tumors (as opposed to high-grade neuroendocrine carcinoma), by
    extrapolation from randomised evidence in lung and gastroenteropancreatic NET.
    The recurrent TSC2 alterations found in thymic neuroendocrine neoplasms provide
    a mechanistic rationale for mTOR-pathway targeting in this tumor family.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: everolimus
      term:
        id: CHEBI:68478
        label: everolimus
  evidence:
  - reference: PMID:40068632
    reference_title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      everolimus and temozolomide are recommended in thymic neuroendocrine tumors.
    explanation: >-
      Review recommending everolimus for the well-differentiated arm. Evidence
      source is OTHER because this is a narrative review and no thymus-specific
      randomised trial exists.
- name: Temozolomide-based chemotherapy
  therapeutic_modality: SMALL_MOLECULE
  action_category: THERAPEUTIC
  description: >-
    Temozolomide, usually combined with capecitabine (CAPTEM), is recommended for
    advanced well-differentiated thymic neuroendocrine tumors. As with everolimus,
    the recommendation rests on extrapolation from lung and gastroenteropancreatic
    NET plus published case series; there is no randomised thymus-specific
    evidence.
  treatment_term:
    preferred_term: Chemotherapy
    term:
      id: NCIT:C15632
      label: Chemotherapy
    therapeutic_agent:
    - preferred_term: temozolomide
      term:
        id: CHEBI:72564
        label: temozolomide
    - preferred_term: capecitabine
      term:
        id: CHEBI:31348
        label: capecitabine
  evidence:
  - reference: PMID:40068632
    reference_title: "A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      everolimus and temozolomide are recommended in thymic neuroendocrine tumors.
    explanation: >-
      Review recommending temozolomide for the well-differentiated arm. Evidence
      source is OTHER because this is a narrative review.
- name: Somatostatin analogue therapy
  therapeutic_modality: PEPTIDE
  action_category: THERAPEUTIC
  target_mechanisms:
  - target: Somatostatin Receptor Expression
    treatment_effect: ACTIVATES
    description: >-
      Octreotide and lanreotide are SSTR2 agonists: they engage the receptor the
      tumor expresses, suppressing hormone secretion and exerting an
      antiproliferative effect.
  - target: Ectopic Corticotropin and CRH Secretion
    treatment_effect: INHIBITS
    description: >-
      SSTR2 agonism suppresses the autonomous peptide-hormone secretion driving the
      paraneoplastic syndrome.
  description: >-
    Long-acting somatostatin analogues (octreotide LAR, lanreotide) are used in
    SSTR2-expressing, DOTATATE-avid thymic neuroendocrine tumors both to control
    hormone hypersecretion and for antiproliferative effect. Patient selection is
    driven by SSTR2 immunohistochemistry and somatostatin-receptor PET, which
    correlate well with one another in thymic epithelial tumors.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: octreotide
      term:
        id: CHEBI:7726
        label: octreotide
    - preferred_term: lanreotide
      term:
        id: CHEBI:135901
        label: lanreotide
  evidence:
  - reference: PMID:35198446
    reference_title: "Correlation of Somatostatin Receptor 2 Expression, 68Ga-DOTATATE PET Scan and Octreotide Treatment in Thymic Epithelial Tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      68Ga-DOTATATE PET scans correlated with SSTR2 expression in TET in most
      patients and appeared to be useful to identify patients with TET who may be
      amenable to treatment with somatostatin analogues.
    explanation: >-
      Supports SSTR2/DOTATATE-guided selection of thymic epithelial tumor patients
      for somatostatin-analogue therapy.
- name: Peptide receptor radionuclide therapy (177Lu-DOTATATE)
  therapeutic_modality: RADIOTHERAPY
  action_category: THERAPEUTIC
  target_mechanisms:
  - target: Somatostatin Receptor Expression
    treatment_effect: INHIBITS
    description: >-
      177Lu-DOTATATE exploits tumoral SSTR2 as a delivery route, internalising a
      beta-emitter that kills the receptor-expressing cell. Receptor expression is
      both the eligibility criterion and the mechanism.
  description: >-
    177Lu-DOTATATE delivers targeted beta radiation to somatostatin-receptor
    expressing tumor cells and is a rational option for progressive, strongly
    SSTR-positive thymic neuroendocrine tumors. Thymic NET is an unlicensed
    indication for Lutathera and is being studied prospectively; use outside a
    trial is off-label and driven by receptor imaging.
  treatment_term:
    preferred_term: Peptide Receptor Radionuclide Therapy
    term:
      id: NCIT:C162449
      label: Peptide Receptor Radionuclide Therapy
    therapeutic_agent:
    - preferred_term: lutetium Lu 177 dotatate
      term:
        id: NCIT:C95020
        label: Lutetium Lu 177 Dotatate
  evidence:
  - reference: clinicaltrials:NCT06121271
    reference_title: "Trial of Lu-177 DOTATATE (Lutathera®) in Unlicensed Indications Including Bronchial and Thymic Neuroendocrine Tumour, Paraganglioma/Phaeochromocytoma, Medullary Thyroid Carcinoma, and Repeat Peptide Receptor Radionuclide Therapy"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The primary objective of this study is to prospectively evaluate the safety
      and efficacy in participants treated with Lu-177 DOTATATE (Lutathera) in
      unresectable or metastatic, somatostatin receptor-expressing neuroendocrine
      tumours (NET) in currently unlicensed indications (eg, bronchial and thymic
      NET
    explanation: >-
      Registered phase 2 trial establishing thymic NET as a target indication for
      177Lu-DOTATATE PRRT and confirming its currently unlicensed status.
- name: Control of hypercortisolism
  therapeutic_modality: OTHER
  action_category: THERAPEUTIC
  context: Ectopic Cushing syndrome subset
  target_mechanisms:
  - target: ACTH-Dependent Hypercortisolism
    treatment_effect: INHIBITS
    description: >-
      Steroidogenesis inhibition, glucocorticoid-receptor blockade or bilateral
      adrenalectomy interrupts the cortisol arm downstream of tumoral ACTH, and
      resection of the primary removes the ACTH source itself.
  description: >-
    In the functional (ectopic-ACTH) subset, urgent control of hypercortisolism is
    a management priority independent of tumor-directed therapy, because severe
    hypercortisolism causes hypokalaemia, hyperglycaemia, thromboembolism and
    life-threatening opportunistic infection. Options include steroidogenesis
    inhibitors, glucocorticoid-receptor blockade and, where the tumor is not
    controllable, bilateral adrenalectomy. Resection of the thymic primary resolves
    the syndrome when the tumor is resectable.
  treatment_term:
    preferred_term: Supportive Care
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:30502716
    reference_title: "Carcinoid tumors of the thymus and Cushing's syndrome: Clinicopathologic features and current best evidence regarding the cell of origin of these unusual neoplasms."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Four (36.4%) of the 11 patients had CS.
    explanation: >-
      Establishes the frequency of the Cushing syndrome that this supportive
      management addresses. Marked PARTIAL because the source characterises the
      syndrome rather than evaluating its treatment.
  - reference: PMID:35690804
    reference_title: "Successful resolution of ectopic Cushing syndrome by minimally invasive thoracoscopic resection of the neuroendocrine tumor of the thymus: a rare case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      following surgery, her blood pressure returned to normal, and the
      hypernatremia/hypopotassemia resolved
    explanation: >-
      Documents resolution of the hypercortisolism-driven hypertension and
      hypokalaemia after resection of the thymic neuroendocrine primary, supporting
      tumor removal as the definitive control of the hormonal syndrome.
- name: Genetic counseling and MEN1 surveillance
  therapeutic_modality: BEHAVIORAL
  action_category: COUNSELING_INFORMATIONAL
  description: >-
    A new diagnosis warrants genetic counseling and germline MEN1 testing, with
    cascade testing of at-risk relatives when a pathogenic variant is found.
    Confirmed MEN1 carriers enter syndrome-directed surveillance including periodic
    thoracic imaging, since thymic tumors in MEN1 are aggressive and systematic
    screening improves prognosis.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:35696052
    reference_title: "Thymic neuroendocrine tumors in patients with multiple endocrine neoplasia type 1."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      TNET in MEN1 patients is an aggressive disease. The prognosis can be better by
      systematic screening.
    explanation: >-
      Supports systematic surveillance of MEN1 patients for thymic neuroendocrine
      tumor.
  - reference: PMID:20301710
    reference_title: "Multiple Endocrine Neoplasia Type 1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      consider chest CT, MRI, or somatostatin receptor scintigraphy octreotide scan
      annually from age 15 years
    explanation: >-
      GeneReviews gives the concrete thoracic surveillance modality and schedule for
      MEN1 carriers, the operational content of this recommendation. Evidence source
      is OTHER because GeneReviews is an expert-curated review.
- name: Prophylactic transcervical thymectomy in MEN1
  therapeutic_modality: SURGERY
  action_category: THERAPEUTIC
  description: >-
    Routine transcervical thymectomy performed at the time of parathyroidectomy has
    been proposed as prophylaxis against thymic carcinoid in MEN1. It is plausible
    and low-cost when the neck is already open, but the supporting evidence
    consists only of observational studies and case reports and does not establish
    that the procedure prevents thymic carcinoid - transcervical thymectomy often
    leaves residual mediastinal thymic tissue. Curated as a syndrome-specific
    expert strategy, not proven prevention.
  treatment_term:
    preferred_term: Thymectomy
    term:
      id: NCIT:C29894
      label: Thymectomy
  evidence:
  - reference: clinicaltrials:NCT05061784
    reference_title: "Revisiting the Evidence for Routine Transcervical Thymectomy for the Prevention of Thymic Carcinoid Tumours in MEN-1 Patients a Case Series"
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A case series was built after review of available literature by searching four
      databases (PubMed, Embase, Medline and Cochrane Library) for observational
      studies or case reports on routine prophylactic TCT for MEN-1 and the
      development of thymic carcinoids.
    explanation: >-
      Documents that the evidence base for prophylactic transcervical thymectomy
      consists of observational studies and case reports. Marked PARTIAL because the
      registry record establishes the study design rather than an efficacy result.
  - reference: PMID:20301710
    reference_title: "Multiple Endocrine Neoplasia Type 1."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Thymectomy may prevent thymic carcinoid in males, particularly in smokers.
    explanation: >-
      GeneReviews states the preventive rationale and its risk-group targeting
      (male sex, smoking) for thymectomy in MEN1. Evidence source is OTHER because
      GeneReviews is an expert-curated review, and the wording ("may prevent") is
      itself the measure of how provisional the recommendation is.
clinical_trials:
- name: NCT06121271
  phase: PHASE_II
  status: RECRUITING
  description: >-
    Open, single-site phase 2 trial of 177Lu-DOTATATE (Lutathera) in unresectable
    or metastatic somatostatin-receptor-expressing neuroendocrine tumours in
    currently unlicensed indications, explicitly including thymic NET. Target
    accrual 75-110 participants receiving four cycles at 8-12 week intervals, with
    two years of follow-up. This is the main prospective study directly relevant to
    PRRT in thymic neuroendocrine carcinoma.
  evidence:
  - reference: clinicaltrials:NCT06121271
    reference_title: "Trial of Lu-177 DOTATATE (Lutathera®) in Unlicensed Indications Including Bronchial and Thymic Neuroendocrine Tumour, Paraganglioma/Phaeochromocytoma, Medullary Thyroid Carcinoma, and Repeat Peptide Receptor Radionuclide Therapy"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This study is a phase 2, open, single-site trial. The primary objective of
      this study is to prospectively evaluate the safety and efficacy in
      participants treated with Lu-177 DOTATATE (Lutathera) in unresectable or
      metastatic, somatostatin receptor-expressing neuroendocrine tumours (NET) in
      currently unlicensed indications (eg, bronchial and thymic NET
    explanation: >-
      Registry record establishing the design, phase and thymic-NET relevance of the
      trial.
- name: NCT05061784
  phase: NOT_APPLICABLE
  status: COMPLETED
  description: >-
    Completed observational case series revisiting the evidence for routine
    transcervical thymectomy as prophylaxis against thymic carcinoid in MEN1
    patients, built on a four-database literature review. Relevant to the
    prevention question rather than to treatment of established disease.
  evidence:
  - reference: clinicaltrials:NCT05061784
    reference_title: "Revisiting the Evidence for Routine Transcervical Thymectomy for the Prevention of Thymic Carcinoid Tumours in MEN-1 Patients a Case Series"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A case series was built after review of available literature by searching four
      databases (PubMed, Embase, Medline and Cochrane Library) for observational
      studies or case reports on routine prophylactic TCT for MEN-1 and the
      development of thymic carcinoids.
    explanation: >-
      Registry record establishing the design and scope of the study.
discussions:
- discussion_id: gap_tnec_population_incidence_by_grade
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What is the actual population incidence of thymic neuroendocrine carcinoma,
    separated from thymoma and conventional thymic carcinoma and stratified by WHO
    grade?
  rationale: >-
    Registry analyses report thymic "cancer" incidence per 100,000 but do not break
    out the neuroendocrine arm, and the largest dedicated series accrue only tens to
    low hundreds of patients across multi-decade windows. Without a grade-stratified
    denominator the prevalence block cannot carry a defensible general-population
    rate, and survival estimates that pool typical carcinoid with high-grade
    neuroendocrine carcinoma are systematically misleading - the published 5-year
    figures in this entry range from 53% to 85% largely because of differing grade
    mixes.
  attaches_to:
  - pathophysiology#Neuroendocrine Clonal Expansion in the Thymus
  proposed_experiments:
  - experiment_id: exp_tnec_multiregistry_incidence
    name: Pooled multi-registry grade-stratified incidence analysis
    description: >-
      Pool SEER with national thymic/NET networks (RYTHMIC, ENDOCAN-RENATEN and
      equivalents) under central pathology review, reporting age-standardised
      incidence separately for typical carcinoid, atypical carcinoid, large cell
      neuroendocrine carcinoma and small cell carcinoma of the thymus.
    would_support:
    - >-
      A grade-stratified per-100,000 incidence that can populate the
      general-population prevalence record with numeric bounds.
    decision_criterion: >-
      Sufficient centrally reviewed cases per grade to estimate incidence with
      confidence intervals excluding zero.
- discussion_id: gap_tnec_cell_of_origin_and_menin_sufficiency
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Does the thymic neuroendocrine cell of origin proposed on immunohistochemical
    grounds - a normal thymic ACTH/CRH-immunoreactive cell - actually give rise to
    thymic neuroendocrine carcinoma, and is menin loss in that cell sufficient for
    transformation?
  rationale: >-
    The cell-of-origin claim currently rests on the observation that non-neoplastic
    thymus contains scattered ACTH- and CRH-immunoreactive cells and that tumors
    from Cushing patients stain more strongly for both. That is a correlational
    immunohistochemical inference, not lineage tracing. No validated mouse model,
    organoid, patient-derived xenograft or canonical cell line for thymic
    neuroendocrine carcinoma was identified in the deep-research sweep, so neither
    the cell of origin nor the sufficiency of menin loss has been tested
    experimentally.
  attaches_to:
  - pathophysiology#Menin Tumor Suppressor Loss
  - pathophysiology#Ectopic Corticotropin and CRH Secretion
  evidence:
  - reference: PMID:30502716
    reference_title: "Carcinoid tumors of the thymus and Cushing's syndrome: Clinicopathologic features and current best evidence regarding the cell of origin of these unusual neoplasms."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The thymus contains CRH and ACTH immunoreactive cells that are probably the
      origin of thymic NET.
    explanation: >-
      The hedged wording ("probably the origin") is itself the evidence that the
      cell of origin remains an inference rather than an established fact.
  proposed_experiments:
  - experiment_id: exp_tnec_thymic_ne_precursor_atlas
    name: Single-cell and spatial atlas of the putative thymic neuroendocrine precursor
    description: >-
      Profile non-neoplastic human thymus by single-cell and spatial transcriptomics
      to define the putative neuroendocrine precursor population, and match its
      signature against thymic neuroendocrine carcinoma tumor transcriptomes.
    would_support:
    - >-
      A transcriptional lineage relationship between a defined normal thymic
      neuroendocrine population and the tumor.
  - experiment_id: exp_tnec_conditional_men1_mouse
    name: Thymic-epithelial-restricted conditional Men1 inactivation
    description: >-
      Conditionally inactivate Men1 in a thymic-epithelial-lineage-restricted mouse
      model to test whether menin loss alone is sufficient to generate thymic
      neuroendocrine tumors.
    would_support:
    - >-
      Menin loss as a sufficient initiating lesion in the thymic epithelial lineage.
    would_refute:
    - >-
      Absence of thymic tumors would indicate that additional cooperating lesions
      (for example RB-axis loss) are required.
- discussion_id: gap_tnec_systemic_therapy_extrapolation
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Is any systemic therapy for advanced thymic neuroendocrine carcinoma supported
    by thymus-specific prospective evidence rather than extrapolation from pulmonary
    and gastroenteropancreatic neuroendocrine neoplasms?
  rationale: >-
    Every systemic option curated in this entry - platinum-etoposide, everolimus,
    temozolomide/CAPTEM, somatostatin analogues, PRRT - is recommended by
    extrapolation. The one prospective study identified (NCT06121271) enrols thymic
    NET only as one of several unlicensed indications. Because thymic neuroendocrine
    neoplasms carry a mutational profile distinct from both thymic carcinoma and
    pulmonary NET (MEN1/MLL2/APC/RB1/TSC2 rather than CDKN2A/TP53), and because they
    are PD-L1-negative unlike the rest of the thymic epithelial family, the
    assumption that efficacy transfers is not safe.
  attaches_to:
  - pathophysiology#RB-Axis Tumor Suppressor Loss
  - pathophysiology#Somatostatin Receptor Expression
  proposed_experiments:
  - experiment_id: exp_tnec_registry_embedded_prospective_cohorts
    name: Registry-embedded prospective systemic-therapy cohorts
    description: >-
      Basket or registry-embedded prospective cohorts within national thymic/NET
      networks reporting objective response and progression-free survival separately
      by WHO grade for platinum-etoposide, everolimus, CAPTEM, somatostatin
      analogues and PRRT.
    would_support:
    - >-
      Grade-specific thymus-native efficacy estimates that would replace the current
      extrapolated recommendations.

📚

References & Deep Research

References

4

PMID:20301710

Multiple Endocrine Neoplasia Type 1.

No top-level findings curated for this source.

PMID:34695605

The 2021 WHO Classification of Tumors of the Thymus and Mediastinum: What Is New in Thymic Epithelial, Germ Cell, and Mesenchymal Tumors?

No top-level findings curated for this source.

PMID:40068632

A Review for the Clinician: Classifications, Genetics, and Treatment for Neuroendocrine Neoplasms of the Thymus (Thymic Carcinoids).

No top-level findings curated for this source.

ORPHA:99869

Thymic neuroendocrine carcinoma

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Thymic Neuroendocrine Carcinoma: Disease-Characteristics Report

Edison Scientific Literature 5 citations 2026-07-31T23:40:01.545166

Thymic Neuroendocrine Carcinoma: Disease-Characteristics Report

Scope and evidence note. “Thymic neuroendocrine carcinoma” is used inconsistently. Some literature uses it broadly for all thymic neuroendocrine neoplasms (Th-NENs), including typical and atypical carcinoids; modern usage usually reserves neuroendocrine carcinoma (NEC) for poorly differentiated small-cell or large-cell carcinoma. This distinction is essential because biology, tempo, imaging phenotype, and treatment differ. Thymus-specific prospective evidence is extremely sparse; therefore, statements extrapolated from pulmonary/extrapulmonary NENs are labeled accordingly.

The following table summarizes ontology-ready findings and the principal uncertainty boundaries.

domain	evidence-based finding	suggested ontology identifiers/terms	evidence limitations
Nomenclature / disease scope	Thymic neuroendocrine neoplasms are rare thymic epithelial tumors; available evidence groups them into well-differentiated carcinoid tumors and high-grade neuroendocrine carcinomas (small-cell and large-cell types). The exact label “thymic neuroendocrine carcinoma” is used inconsistently across sources, so knowledge-base entries should preserve both the broad thymic NEN umbrella and the high-grade NEC subset (OpenTargets Search: thymic neuroendocrine carcinoma, nicoli2023epigeneticsofthymic pages 2-3).	MONDO: MONDO_0020516 thymic neuroendocrine carcinoma; MONDO: thymic large cell neuroendocrine carcinoma MONDO_0003047; MONDO: thymus small cell carcinoma MONDO_0004122; NCIT/MeSH IDs: unavailable here	WHO-class wording is partly inferred from review-level summaries; no directly retrieved WHO monograph text or full thymus-specific pathology paper in context.
Resource level	Most facts here are aggregated disease-level literature/guideline/trial-registry findings rather than individual EHR-derived observations (OpenTargets Search: thymic neuroendocrine carcinoma, NCT05061784 chunk 1).	Evidence type tag: aggregated literature / registry / trial registry	Not a patient-level dataset.
Anatomy	Primary site is the thymus in the anterior mediastinum; thymic NETs are described as aggressive mediastinal tumors (nicoli2023epigeneticsofthymic pages 2-3).	UBERON: thymus UBERON:0002370; UBERON: mediastinum UBERON:0003406; anatomy qualifier: anterior mediastinum ID unavailable here	“Anterior mediastinum” ontology accession not verified in retrieved context.
Principal phenotype: mass effect / thoracic presentation	Approximate/extrapolated: anterior mediastinal tumors commonly present with local mass-effect symptoms such as cough, chest pain, dyspnea, or may be incidentally detected; this is consistent with thymic epithelial tumor guidance but not directly quantified for thymic NEC in retrieved context (OpenTargets Search: thymic neuroendocrine carcinoma).	HPO suggestions: Chest pain HP:0100749; Cough HP:0012735; Dyspnea HP:0002094; Mediastinal mass ID unavailable here	Largely extrapolated from thymic epithelial tumor practice and thoracic oncology, not directly enumerated in retrieved thymic NEC abstracts.
Principal phenotype: endocrine syndromes	About 50% of thymic NET manifestations were reported in one review summary as associated with endocrinopathies, including Cushing syndrome and acromegaly; endocrine secretion can strongly affect quality of life (nicoli2023epigeneticsofthymic pages 2-3).	HPO: Cushing syndrome HP:0002664; Hypercortisolism HP:0000846; Ectopic ACTH secretion ID unavailable here	Figure comes from a narrative review summary and may reflect pooled historical literature; not necessarily specific to only high-grade NEC.
Principal phenotype: hereditary association	Thymic NETs/carcinoids are associated with MEN1; available sources note this association and describe prophylactic thymectomy/surveillance questions in MEN1 populations (nicoli2023epigeneticsofthymic pages 2-3, NCT05061784 chunk 1).	MONDO: multiple endocrine neoplasia type 1 ID unavailable here; OMIM MEN1 syndrome ID not verified here; gene MEN1 (HGNC:7010)	MEN1 association is strongest for thymic carcinoid / thymic NET broadly, not proven for every thymic NEC subtype.
Pathology / neuroendocrine differentiation markers	Neuroendocrine tumors are typically confirmed by neuroendocrine-marker expression; practical markers for ontology-ready annotation include synaptophysin, chromogranin A, and INSM1; cytokeratin supports epithelial nature; Ki-67 helps grading/proliferation assessment. General NEN reviews also note chromogranin A and synaptophysin as diagnostic markers (nicoli2023epigeneticsofthymic pages 2-3).	Proteins/genes: SYP, CHGA, INSM1, broad-spectrum keratins (KRT8/KRT18/KRT19 approximate), MKI67; NCIT marker terms: unavailable here	Synaptophysin/chromogranin use is strongly standard but not directly enumerated in a thymus-specific primary study in retrieved context; INSM1 is included as current practice but extrapolated.
Pathology / SSTR biology	Somatostatin receptor subtypes are expressed in neuroendocrine neoplasms, with SSTR2A particularly prominent; a study across NENs concluded NECs may be candidates for somatostatin-analogue targeting and that SSTR2A can serve as a biomarker of neuroendocrine differentiation (OpenTargets Search: thymic neuroendocrine carcinoma).	Gene/protein: SSTR2; IHC marker: SSTR2A; CHEBI class: somatostatin analogues	Not thymus-specific; based on mixed-site NENs/NECs.
Molecular distinction	Current understanding supports a biologic split: MEN1-associated / carcinoid-like disease for well-differentiated thymic NETs versus TP53/RB1-altered high-grade NEC-like biology for poorly differentiated NECs. Open Targets currently shows no direct curated target evidence rows for MONDO_0020516, so TP53/RB1 annotation should be flagged as approximate/extrapolated from large-cell NEC and general NEC biology (OpenTargets Search: thymic neuroendocrine carcinoma, nicoli2023epigeneticsofthymic pages 2-3).	Gene terms: MEN1, TP53, RB1, possibly CDKN2A; GO: regulation of cell cycle GO:0051726, apoptotic process GO:0006915	Strong caveat: TP53/RB1 evidence in context is not thymus-specific primary sequencing for MONDO_0020516; direct molecular data remain sparse.
Metastatic pattern	Thymic NETs are described as aggressive and capable of metastasizing to liver, lymph nodes, bone, lung, and brain (nicoli2023epigeneticsofthymic pages 2-3).	HPO suggestions: Hepatic metastases HP:0007340; Lymph node metastases HP:0005276; Bone metastases ID unavailable here; Brain metastases ID unavailable here	Review-level statement; site-specific frequencies not available in retrieved context.
Epidemiology / rarity	Thymic neuroendocrine tumors are ultra-rare. In SEER-based analysis of 2000-2018, 263 thymic NET patients were identified; another recent epidemiology paper confirms thymic NETs are part of the rare TET spectrum (OpenTargets Search: thymic neuroendocrine carcinoma).	MONDO rarity annotation applicable; Orphanet ID unavailable here	No precise population incidence per 100,000 for thymic NET alone in retrieved context.
Second malignancy risk	In SEER analysis, thymic NET patients had increased risk of second malignancies with SIR 1.73 (95% CI 1.13-2.54); 19/263 thymic NET patients developed second malignancies and age at diagnosis was a significant risk factor (OpenTargets Search: thymic neuroendocrine carcinoma).	HPO/NCIT terms for second primary malignancy: ID unavailable here	Applies to thymic NET broadly, not only high-grade NEC.
Diagnostics / imaging	Approximate/current practice: diagnosis relies on thoracic imaging plus tissue biopsy; functional imaging may include somatostatin-receptor imaging when SSTR-positive disease is suspected, especially for therapeutic selection (OpenTargets Search: thymic neuroendocrine carcinoma).	Rad/biomarker suggestions: CT chest; MRI as needed; SSTR PET/CT (e.g., Ga-68 DOTATATE, CHEBI/NCIT IDs unavailable here)	Imaging workflow is partly extrapolated from general NET and thymic epithelial tumor practice; no thymus-specific imaging trial in retrieved context.
Diagnostics / histology	Histologic confirmation should record neuroendocrine morphology, epithelial differentiation, and proliferative index. For ontology curation, capture tumor type (carcinoid vs small-cell NEC vs large-cell NEC), marker panel, necrosis, and Ki-67/mitotic activity (OpenTargets Search: thymic neuroendocrine carcinoma, nicoli2023epigeneticsofthymic pages 2-3).	NCIT disease classes unavailable here; genes/proteins: MKI67, SYP, CHGA, INSM1, keratins	Detailed cutoff values and consensus thymus-specific grading text were not present in retrieved context.
Treatment classes	Surgery remains the principal treatment for resectable thymic epithelial tumors; systemic options across thymic NET/NEN practice may include chemotherapy, somatostatin analogues, everolimus, temozolomide-based regimens/CAPTEM, PRRT, and occasionally immunotherapy, but much of this is extrapolated from non-thymic or mixed thoracic NET literature (OpenTargets Search: thymic neuroendocrine carcinoma).	NCIT intervention suggestions: Surgical Resection; Chemotherapy; Somatostatin Analog Therapy; Everolimus Therapy; Temozolomide Regimen; Capecitabine/Temozolomide Regimen; Peptide Receptor Radionuclide Therapy; Immune Checkpoint Inhibitor Therapy	Direct thymus-specific comparative efficacy data were not retrieved; several treatment labels are extrapolated/current-practice rather than proven in thymic NEC.
Current real-world / trial implementations	Ongoing or recent studies relevant to thymic NET include NCT06121271 (phase II Lu-177 DOTATATE in unlicensed indications; planned enrollment 110), NCT07429851 (observational comparison of thymic/pulmonary/pancreatic well-differentiated high-grade NETs; enrollment 34), and NCT05061784 (routine transcervical thymectomy in MEN1; completed, n=7) (NCT05061784 chunk 1).	ClinicalTrials.gov: NCT06121271, NCT07429851, NCT05061784	Trials are not specific to thymic neuroendocrine carcinoma alone; some focus on NETs or MEN1 prevention rather than established NEC treatment.
Prevention / MEN1 surveillance	In MEN1, prophylactic or routine transcervical thymectomy at time of parathyroid surgery has been used to reduce thymic carcinoid risk, but efficacy data are described as scarce; surveillance remains important (NCT05061784 chunk 1).	Preventive intervention: transcervical thymectomy; genetic counseling; MEN1 surveillance protocol IDs unavailable here	Evidence base is limited, observational, and focused on MEN1-associated thymic carcinoid risk rather than sporadic thymic NEC.
Prognosis / natural history	Available sources characterize thymic NETs as aggressive with metastatic potential and relatively limited chemotherapy responsiveness (nicoli2023epigeneticsofthymic pages 2-3).	HPO suggestions: Neoplasm metastasis HP:0002664 approximate broad cancer term unavailable; progressive disease term unavailable here	No robust retrieved survival percentages specific to MONDO_0020516.
Cell/tissue ontology suggestions	Tumor likely arises from thymic epithelial/neuroendocrine differentiated cells within thymic tissue; annotate epithelial tumor with neuroendocrine differentiation (nicoli2023epigeneticsofthymic pages 2-3).	CL: neuroendocrine cell term approximate CL:0000165; thymic epithelial cell term ID unavailable here; GO CC: nucleus/cytoplasm markers not specific	Precise thymic cell-of-origin remains uncertain; CL terms not fully verified in retrieved context.
Model systems	No disease-specific validated model organisms or cell-line resources were identified in retrieved context for thymic neuroendocrine carcinoma; use “not established / not retrieved” in the knowledge base.	Model organism/resource IDs unavailable	Important knowledge gap.

Table: This table provides an ontology-ready summary of thymic neuroendocrine carcinoma/neoplasms, emphasizing what is directly supported in the retrieved evidence versus what is approximate or extrapolated. It is designed to help populate structured disease knowledge-base fields while preserving uncertainty.

1. Disease information

Th-NENs are malignant epithelial neoplasms arising in the thymus and showing neuroendocrine morphology and marker expression. The family comprises well-differentiated typical/atypical carcinoids and poorly differentiated small-cell/large-cell NECs. They are among the rarest thymic epithelial tumors and account for approximately 0.4% of carcinoid tumors in one recent review synthesis. They typically occupy the anterior mediastinum and may invade adjacent mediastinal structures or metastasize to lymph nodes, liver, bone, lung, and brain. (nicoli2023epigeneticsofthymic pages 2-3)

Identifiers and synonyms

MONDO: MONDO:0020516, thymic neuroendocrine carcinoma.
Subclasses include MONDO:0003047, thymic large-cell neuroendocrine carcinoma, and MONDO:0004122, thymus small-cell carcinoma. Open Targets returned no directly curated target associations for either thymic-specific entity. (OpenTargets Search: thymic neuroendocrine carcinoma)
Synonyms: thymic neuroendocrine neoplasm/tumor, neuroendocrine tumor of thymus, thymic carcinoid, thymic typical carcinoid, thymic atypical carcinoid, thymic small-cell carcinoma, thymic large-cell neuroendocrine carcinoma.
ICD-10 generally requires a site-plus-morphology approach; C37 denotes malignant neoplasm of thymus but does not encode neuroendocrine histology. A specific ICD-11/OMIM/Orphanet identifier was not verified in the retrieved evidence.
The evidence is aggregated disease-level literature, registry research, and trial-registry information—not individual-patient EHR data.

2. Etiology and risk factors

Most cases are sporadic, and no established environmental, infectious, dietary, smoking, occupational, or radiation cause is known. Consequently, no validated lifestyle-based protective factor or gene–environment interaction has been demonstrated.

The best-established inherited predisposition is multiple endocrine neoplasia type 1 (MEN1), caused by pathogenic germline loss-of-function variants in MEN1 and inherited autosomal dominantly. The association applies most clearly to thymic carcinoids/well-differentiated Th-NETs, not necessarily to every poorly differentiated NEC. Menin participates in transcriptional and chromatin-regulatory networks, providing a plausible tumor-suppressor mechanism. Thymic NETs are clinically important causes of mortality in MEN1. (nicoli2023epigeneticsofthymic pages 2-3)

For a patient with Th-NEN—particularly a young patient, multifocal endocrine disease, hyperparathyroidism, pituitary or pancreatic NET, or suggestive family history—genetic counseling and germline MEN1 testing are appropriate. No reproducible protective allele, modifier gene, founder effect, carrier frequency, anticipation, or germline-mosaicism estimate specific to Th-NEN was identified.

3. Phenotypes

Presentation is heterogeneous and often insidious.

Local mass effects: cough (HP:0012735), dyspnea (HP:0002094), chest pain (HP:0100749), superior vena cava obstruction, or an incidentally detected anterior mediastinal mass. These manifestations may progress as the lesion enlarges; thymus-specific frequencies were unavailable.
Endocrine/paraneoplastic manifestations: ectopic ACTH secretion can cause hypercortisolism (HP:0000846) and Cushing syndrome (HP:0002664), including hypertension, diabetes, hypokalemia, infections, muscle weakness, and osteoporosis. Acromegaly and other secretory syndromes are reported but less characteristic. One review summarized endocrinopathy associations in approximately 50% of thymic NET manifestations, although this historical pooled estimate should not be interpreted as the frequency in high-grade NEC alone. (nicoli2023epigeneticsofthymic pages 2-3)
Metastatic disease: lymph-node, liver, skeletal, pulmonary, or cerebral metastases may produce pain, neurologic impairment, respiratory compromise, or organ dysfunction. (nicoli2023epigeneticsofthymic pages 2-3)
Quality of life: thoracic symptoms, hormone excess, treatment toxicity, anxiety about recurrence, and MEN1-related multiple tumors can substantially impair physical and psychosocial functioning. No validated Th-NEN-specific EQ-5D, SF-36, or PROMIS dataset was retrieved.

4. Genetic and molecular information

There is no single somatic variant that defines all Th-NENs.

MEN1: germline pathogenic variants cause MEN1 syndrome; tumorigenesis usually follows biallelic tumor-suppressor inactivation. Sporadic well-differentiated NETs may also acquire somatic MEN1-pathway alterations. Exact thymus-specific variant spectra and allele frequencies were not available.
High-grade NEC framework: loss of TP53 and RB1 function is a central model for poorly differentiated NEC, causing checkpoint failure, genomic instability, and rapid proliferation. However, Open Targets found zero direct target-association rows for MONDO:0020516; TP53/RB1 evidence in the retrieved database pertains to large-cell NEC across sites and must not be represented as proven universal thymic causation. Other cross-site LCNEC-associated genes include IDH2, SMARCA4, CDKN2A, BRAF, STK11, and KEAP1. (OpenTargets Search: thymic neuroendocrine carcinoma)
Variant interpretation: tumor-panel variants should be classified as somatic oncogenic alterations using AMP/ASCO/CAP criteria, while suspected germline variants require ACMG/AMP interpretation. Tumor-only detection of a MEN1 alteration does not establish hereditary MEN1.
Epigenetics/omics: thymic epithelial tumors show methylation, histone, and noncoding-RNA dysregulation, but neuroendocrine-subtype-specific epigenomic, transcriptomic, proteomic, metabolomic, lipidomic, single-cell, spatial, and CRISPR-screen datasets remain inadequate. (nicoli2023epigeneticsofthymic pages 2-3)
No recurrent thymus-specific translocation, aneuploidy, pathogenic structural variant, or validated modifier gene was established.

5. Environmental information

No infectious agent or transmissible process is implicated. Evidence does not support smoking, alcohol, diet, exercise, pollution, or occupational toxins as established causal factors. Apparent associations from pulmonary small-cell/large-cell NEC should not be transferred to a primary thymic tumor without site confirmation. Environmental primary prevention is therefore unavailable beyond general cancer-health recommendations.

6. Mechanism and pathophysiology

A cautious causal model is:

Upstream initiation: inherited or somatic tumor-suppressor disruption—MEN1/menin biology particularly in well-differentiated thymic NET, or TP53–RB1 checkpoint loss in the extrapolated high-grade NEC model.
Cellular transformation: altered chromatin/transcription, defective G1/S control, resistance to apoptosis, genomic instability, and clonal expansion of a thymic epithelial cell with neuroendocrine differentiation.
Tumor phenotype: expression of synaptophysin, chromogranin A, INSM1, and sometimes somatostatin receptors; increasing mitoses, Ki-67 labeling, and necrosis accompany aggressive disease.
Local/systemic consequences: mediastinal invasion causes compression; lymphatic/hematogenous spread causes distant disease; secretion of ACTH or other peptides produces endocrine syndromes.

Suggested ontology annotations include regulation of cell cycle (GO:0051726), apoptotic process (GO:0006915), DNA-damage response, chromosome segregation, hormone secretion, epithelial-cell proliferation, and neuroendocrine cell differentiation. Candidate cell terms are neuroendocrine cell (CL:0000165) and thymic epithelial cell; precise cell of origin remains unresolved. SSTR2 expression offers a mechanistic link to somatostatin-receptor imaging, somatostatin analogues, and peptide-receptor radionuclide therapy, although retrieved receptor evidence was derived from mixed-site NENs rather than a thymus-specific cohort.

7. Anatomical structures affected

The primary organ is the thymus (UBERON:0002370), usually in the anterior mediastinum; mediastinum may be annotated UBERON:0003406. Disease can extend into mediastinal fat, pleura, pericardium, lung, great vessels, or chest wall and spread to regional lymph nodes. Common distant sites include liver, bone, lung, and brain. (nicoli2023epigeneticsofthymic pages 2-3)

At tissue level, this is an epithelial malignancy with neuroendocrine differentiation. Relevant subcellular compartments include the nucleus for menin, p53, RB, and Ki-67; cytoplasm/secretory vesicles for chromogranin and synaptophysin; and plasma membrane for SSTR2. Lateralization is not meaningful.

8. Temporal development

Typical onset is in adulthood, although pediatric and young-adult MEN1-associated cases occur. The onset is generally chronic and occult rather than acute; hormone secretion may bring earlier recognition.

Course depends strongly on differentiation and stage. Typical carcinoid is usually more indolent, atypical carcinoid intermediate, and small-/large-cell NEC rapidly progressive. Nevertheless, even well-differentiated thymic carcinoids can recur late. Disease is staged anatomically using contemporary thymic-tumor TNM practice, while older studies often use Masaoka-Koga categories; these systems should not be conflated. Complete resection offers the principal chance of durable remission, but prolonged surveillance is justified because late local or distant recurrence occurs. No spontaneous-remission pattern or validated critical developmental window is known.

9. Inheritance, epidemiology, and population

This is an ultra-rare cancer. A SEER analysis identified 263 thymic NET patients from 2000–2018; a reliable standalone population incidence per 100,000 was not available in the retrieved evidence. In that cohort, 19/263 developed a second malignancy. The standardized incidence ratio was 1.73 (95% CI 1.13–2.54), and the reported age-adjusted second-cancer incidence was 4,178.46 per 100,000 persons. Older age at diagnosis was a significant risk factor. These values apply to thymic NET broadly, not exclusively poorly differentiated NEC. (OpenTargets Search: thymic neuroendocrine carcinoma)

MEN1 predisposition is autosomal dominant, with age-dependent and variable expression of the syndrome; Th-NEN itself is not inherited as an isolated Mendelian cancer in most patients. Reliable disease-specific penetrance, ethnic prevalence, geographic gradients, founder variants, and sex ratio were not established in the retrieved evidence.

10. Diagnostics

Imaging. Contrast-enhanced chest CT is the primary anatomical study; MRI helps assess vascular, cardiac, or spinal involvement. FDG-PET/CT can support staging of aggressive NEC. Somatostatin-receptor PET/CT—such as gallium-68 DOTATATE—is useful when well-differentiated or SSTR-positive disease is suspected and for selecting somatostatin-analogue or PRRT strategies. Brain and bone imaging are symptom/stage directed.

Pathology. Diagnosis requires tissue. Record architecture, cytology, mitotic activity, necrosis, Ki-67 index, lymphovascular invasion, and neuroendocrine differentiation. A practical panel includes pancytokeratin, synaptophysin, chromogranin A, and INSM1, with Ki-67 for proliferation. Additional markers help exclude mimics and determine origin; a mediastinal neuroendocrine carcinoma must be distinguished from pulmonary metastasis/direct extension, lymphoma, thymoma, thymic squamous carcinoma, paraganglioma, germ-cell tumor, and metastatic NET from another organ. Serum chromogranin A is nonspecific; ACTH/cortisol and other hormones should be tested when clinically indicated.

Genetics. Germline MEN1 sequencing plus deletion/duplication analysis is appropriate when hereditary disease is suspected. Broad tumor NGS may identify actionable alterations in advanced disease, but WES/WGS, RNA-seq, methylation testing, CMA, karyotyping, FISH, mitochondrial, and repeat-expansion tests are not routine diagnostic requirements. No population screening is recommended. MEN1 carriers require syndrome-directed surveillance.

11. Outcome and prognosis

Th-NENs are characterized as aggressive, metastasis-prone neoplasms with limited chemotherapy responsiveness, although this generalization spans biologically different subtypes. (nicoli2023epigeneticsofthymic pages 2-3) Major adverse prognostic factors are poorly differentiated/small-cell or large-cell histology, advanced stage, incomplete resection, lymph-node or distant metastasis, high proliferative activity, tumor necrosis, hormone-mediated morbidity, and progression despite systemic therapy.

No sufficiently robust, subtype-specific 5- or 10-year survival estimate was recovered for MONDO:0020516; reporting a pooled percentage would risk mixing carcinoid and NEC. Important complications include mediastinal compression, endocrine crises, metastatic organ dysfunction, recurrence, treatment toxicity, and second primary malignancies. The elevated second-cancer risk supports long-term, individualized follow-up. (OpenTargets Search: thymic neuroendocrine carcinoma)

12. Treatment and current applications

Management should occur in a multidisciplinary thymic/NET center.

Localized/resectable disease: complete en-bloc surgical resection, generally with appropriate regional lymph-node assessment, is the preferred curative strategy. Consider postoperative radiotherapy for incomplete margins, locally advanced disease, or selected high-risk pathology. NCIt suggestions: Surgical Resection; Thymectomy; Lymph-Node Dissection; Adjuvant Radiation Therapy.
High-grade NEC: platinum plus etoposide is commonly used by extrapolation from pulmonary/extrapulmonary NEC, including neoadjuvant, adjuvant, or metastatic settings. Toxicities include myelosuppression, infection, nausea, renal/neurologic toxicity, and alopecia. Direct thymus-specific comparative trials are lacking.
Well-differentiated/SSTR-positive disease: somatostatin analogues can control hormone secretion and may stabilize disease; everolimus is used by extrapolation from lung/GEP NET evidence. Temozolomide-based treatment, often CAPTEM, is increasingly reported in advanced thymic NET, but robust randomized thymus-specific response estimates are unavailable.
PRRT: lutetium-177–labeled somatostatin analogues are a rational option for progressive, strongly SSTR-positive disease. Relevant current studies include NCT06121271, a planned phase II study of Lu-177 DOTATATE in unlicensed indications, including thymic NET (planned n=110). A thymus-inclusive Lu-177 DOTATOC study, NCT04276597, was withdrawn with no enrollment.
Immunotherapy/targeted therapy: checkpoint blockade may be considered selectively in refractory high-grade disease, but efficacy is uncertain and thymic-tumor immune toxicities warrant caution. Molecularly matched therapy should depend on a validated actionable alteration rather than histology alone.
Hormonal/supportive care: control hypercortisolism urgently when present; manage pain, nutrition, infection, thrombosis, cardiopulmonary compromise, and treatment-related disability. Rehabilitation should be individualized.

Other relevant studies include NCT07429851, an observational comparison of thymic, pulmonary, and pancreatic well-differentiated high-grade NETs (planned n=34), and NCT06141369, an individualized mRNA-neoantigen-vaccine study enrolling advanced endocrine tumors. These are not dedicated randomized Th-NEC trials.

No CPIC or PharmGKB genotype-guided regimen is established for this disease, and gene, cell, or RNA therapies are not standard.

13. Prevention

There is no proven primary prevention for sporadic disease, no applicable vaccine, and no population screening program. In MEN1, genetic counseling, cascade testing, and periodic thoracic imaging represent secondary prevention/early detection.

Routine transcervical thymectomy performed during MEN1 parathyroid surgery has been proposed as prophylaxis against thymic carcinoid. NCT05061784 was a completed seven-person observational study of this approach with follow-up up to 100 months; its registry summary emphasizes that efficacy evidence remains scarce. Thus, prophylactic thymectomy should be represented as a syndrome-specific expert strategy, not proven universal prevention. (NCT05061784 chunk 1)

Tertiary prevention comprises complete initial staging/resection, endocrine control, recurrence surveillance, and age-appropriate screening for second primary cancers. The observed SIR of 1.73 supports prolonged follow-up but does not by itself define a special screening schedule. (OpenTargets Search: thymic neuroendocrine carcinoma)

14. Other species and natural disease

No well-characterized naturally occurring homolog of human thymic NEC in a companion animal or wildlife species was identified. Sporadic thymic and neuroendocrine tumors occur in animals, but comparative equivalence is unproven. The disease is noninfectious, nontransmissible, and nonzoonotic. MEN1, TP53, RB1, and core cell-cycle pathways are evolutionarily conserved, but this alone does not establish an animal disease model. NCBI Taxon 9606 applies to the human disease.

15. Model organisms and experimental systems

No validated, widely adopted Th-NEN-specific mouse model, patient-derived xenograft, organoid, iPSC model, or canonical cell line was identified in the retrieved evidence. Generic MEN1-deficient endocrine-tumor models can interrogate menin biology, and TP53/RB1-deficient pulmonary NEC models can study high-grade neuroendocrine transformation, but neither fully reproduces the thymic microenvironment or complete histologic spectrum. This is a major research gap affecting biomarker validation, drug screening, and mechanistic inference.

Recent developments and authoritative interpretation

The most important 2023–2024 developments are improved separation of well-differentiated NET from poorly differentiated NEC, increasing use of molecular profiling and SSTR imaging to select systemic therapy, prospective investigation of PRRT in non-GEP sites, and registry-based quantification of second-malignancy risk. The January 2024 SEER analysis concluded that thymic NET patients have a significantly increased second-cancer risk; its abstract reported 263 patients, 19 second malignancies, and SIR 1.73. (OpenTargets Search: thymic neuroendocrine carcinoma)

The principal expert conclusion is that precision begins with correct classification. Combining carcinoid and high-grade NEC creates misleading survival, molecular, and treatment estimates. Current evidence supports surgery for resectable disease, MEN1 assessment where indicated, SSTR-directed approaches for receptor-positive well-differentiated tumors, and platinum-based therapy for poorly differentiated NEC. For many other decisions, referral-center consensus and cross-site extrapolation remain necessary.

Selected sources and dates

Nicolì V, Coppedè F. Epigenetics of Thymic Epithelial Tumors. Cancers. Published January 2023. DOI: https://doi.org/10.3390/cancers15020360. The review states that the neuroendocrine forms are the “rarest and aggressive” thymic epithelial tumors and emphasizes the need for integrated genetic, epigenetic, and expression studies. (nicoli2023epigeneticsofthymic pages 2-3)
Qiu G, Wang F, Wang Y. Incidence of second malignancies in patients with thymic carcinoma and thymic neuroendocrine tumor. Journal of Cancer Research and Clinical Oncology. Published January 2024. DOI: https://doi.org/10.1007/s00432-023-05522-3. Its abstract concludes: “The incidence of second malignancies in patients with thymic carcinoma and thymic NET is significantly higher than the patients in the normal population.” (OpenTargets Search: thymic neuroendocrine carcinoma)
ClinicalTrials.gov. Routine Transcervical Thymectomy in MEN-1 Patients. Completed August 2021. NCT05061784: https://clinicaltrials.gov/study/NCT05061784. (NCT05061784 chunk 1)
Open Targets disease record, MONDO:0020516, accessed through the current database search; no direct target associations were returned for thymic neuroendocrine carcinoma. (OpenTargets Search: thymic neuroendocrine carcinoma)

Evidence limitation: PMID values were not present in the retrieved full-text evidence for the principal recent papers, so DOI and registry identifiers are supplied rather than inferred. Exact survival rates, phenotype frequencies, somatic-variant frequencies, and treatment response rates should remain null/unknown in a knowledge base unless tied to a clearly defined histologic subtype and source cohort.

References

(OpenTargets Search: thymic neuroendocrine carcinoma): Open Targets Query (thymic neuroendocrine carcinoma, 18 results). Buniello, A. et al. (2025). Open Targets Platform: facilitating therapeutic hypotheses building in drug discovery. Nucleic Acids Research.
(nicoli2023epigeneticsofthymic pages 2-3): Vanessa Nicolì and Fabio Coppedè. Epigenetics of thymic epithelial tumors. Jan 2023. URL: https://doi.org/10.3390/cancers15020360, doi:10.3390/cancers15020360. This article has 12 citations.
(NCT05061784 chunk 1): Rajeev Parameswaran. Routine Transcervical Thymectomy in MEN-1 Patients. National University Health System, Singapore. 2021. ClinicalTrials.gov Identifier: NCT05061784

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Thymic Neuroendocrine Carcinoma: Disease-Characteristics Report

1. Disease information

2. Etiology and risk factors

3. Phenotypes

4. Genetic and molecular information

5. Environmental information

6. Mechanism and pathophysiology

7. Anatomical structures affected

8. Temporal development

9. Inheritance, epidemiology, and population

10. Diagnostics

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12. Treatment and current applications

13. Prevention

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Recent developments and authoritative interpretation

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