Salivary Gland Polymorphous Adenocarcinoma

Cancer MONDO:0000521 Pathograph 13 Show in embeddings browser salivary gland carcinoma

Polymorphous adenocarcinoma (PAC) is a low-grade malignant epithelial neoplasm of salivary gland origin with a striking predilection for the minor salivary glands of the palate. It is probably the second most common malignancy of the minor salivary glands, after adenoid cystic carcinoma (ACC). The name refers to architectural, not cytological, diversity: a single tumor displays tubular, trabecular, cribriform, papillary, solid, and single-file patterns and characteristically streams into concentric whorls around nerves, while the constituent cells remain bland and monomorphic. That combination of cytological uniformity with architectural variability is the diagnostic signature, and the basis for separating PAC from ACC and pleomorphic adenoma, which occupy the same anatomic site and overlap cytologically. Most conventional PAC is driven by a recurrent activating hotspot mutation in PRKD1 (p.Glu710Asp), while rearrangements of PRKD1, PRKD2, or PRKD3 characterize the cribriform subtype; the two lesion classes are mutually exclusive and converge on deregulated protein kinase D signaling, placing PAC among the tumors defined by a single pathway rather than a single mutation. Behavior is indolent, with frequent perineural invasion that does not carry the adverse prognostic weight it does in ACC, low rates of distant metastasis, and very low disease-specific mortality (pooled series report figures from around 3% down to none). The principal clinically actionable split within the entity is nodal risk: fusion-positive/cribriform tumors metastasize to neck nodes at a much higher rate than hotspot-mutant/classic tumors.

Ask OpenScientist

Ask a research question about Salivary Gland Polymorphous Adenocarcinoma. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

1
Mappings
6
Pathophys.
9
Histopath.
5
Phenotypes
2
Hypotheses
5
Gaps
13
Pathograph
5
Genes
3
Medical Actions
2
Subtypes
12
References
1
Deep Research
🏷

Classifications

ICD-O Morphology
Carcinoma
Harrison's Part
ONCOLOGY HEMATOLOGY
🔗

Mappings

NCIT
NCIT:C35702 Salivary Gland Polymorphous Adenocarcinoma
skos:exactMatch NCIT
NCIT is the only ontology in the dismech constrained set that codes this entity. MONDO has no polymorphous adenocarcinoma class (searched labels and exact synonyms), so disease_term is anchored to the nearest MONDO superclass, salivary gland carcinoma, and exact entity identity is carried here. The MONDO gap is recorded as an open discussion.
NCIT
NCIT:C35702 Salivary Gland Polymorphous Adenocarcinoma
skos:exactMatch NCIT
NCIT is the only ontology in the dismech constrained set that codes this entity. MONDO has no polymorphous adenocarcinoma class (searched labels and exact synonyms), so disease_term is anchored to the nearest MONDO superclass, salivary gland carcinoma, and exact entity identity is carried here. The MONDO gap is recorded as an open discussion.
◆

Subtypes

2
Conventional (classic) polymorphous adenocarcinoma NCIT:C201781
PRKD1 hgnc:9407 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in PRKD1 (hgnc:9407). hgnc:9407 is a gene from the HUGO Gene Nomenclature Committee.
The classic form, overwhelmingly palatal, showing tubular, trabecular, microcystic, solid, and papillary-cystic architecture with mucinous, myxoid, or hyalinized stroma and frequent perineural involvement. It is the subtype enriched for the PRKD1 p.Glu710Asp hotspot mutation and rarely involves regional lymph nodes.
Show evidence (1 reference)
PMID:37595638 SUPPORT Human Clinical
"While conventional PACs are most associated with PRKD1 p.E710D hotspot mutations, the cribriform subtype is often associated with gene fusions in PRKD1, PRKD2, or PRKD3."
States the genotype split between the conventional and cribriform subtypes that defines this subtype division.
Cribriform subtype (cribriform adenocarcinoma of salivary gland, CASG) NCIT:C201786
PRKD1 hgnc:9407 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in PRKD1 (hgnc:9407). hgnc:9407 is a gene from the HUGO Gene Nomenclature Committee. PRKD2 hgnc:17293 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in PRKD2 (hgnc:17293). hgnc:17293 is a gene from the HUGO Gene Nomenclature Committee. PRKD3 hgnc:9408 HUGO Gene Nomenclature Committee (hgnc) Relation: this subtype is caused by variation in this gene This subtype is caused by variation in PRKD3 (hgnc:9408). hgnc:9408 is a gene from the HUGO Gene Nomenclature Committee.
A subtype with predominantly cribriform and multinodular architecture, a predilection for the base of tongue rather than the palate, and a markedly higher rate of regional lymph node metastasis at presentation. It is enriched for PRKD1/PRKD2/PRKD3 rearrangements rather than the PRKD1 hotspot mutation. Whether it is a subtype of PAC or a separate entity remains contested; the WHO classification places it under the PAC heading.
Show evidence (1 reference)
PMID:34023291 SUPPORT Human Clinical
"PAC and CAC both show median age of diagnosis in the sixth decade of life and a female predominance. CAC occurs most frequently in the tongue and PAC in the palate."
Establishes the site difference (tongue versus palate) that distinguishes the cribriform subtype from conventional PAC.
◈

Mechanistic Hypotheses

2
Single PRKD-Driven Spectrum Model
prkd_convergent_spectrum CANONICAL
Evidence balance 1 support
Conventional PAC, cribriform adenocarcinoma, indeterminate tumors, and papillary-predominant tumors form one biological spectrum unified by alterations of the PRKD gene family, with the specific lesion (hotspot mutation versus rearrangement) explaining the morphological and nodal-risk differences rather than marking separate diseases. This is the position taken by the WHO classification, which places cribriform adenocarcinoma under the PAC heading, and is supported by the shared PRKD genotype across the spectrum and by the mutual exclusivity of the two lesion classes.
Show evidence (1 reference)
PMID:31492931 SUPPORT Human Clinical
"These findings show that polymorphous adenocarcinoma, cribriform adenocarcinoma, tumor with indeterminate features and tumor with predominant papillary pattern display marked genetic overlap, and suggest that they may represent a spectrum of lesions driven by PRKD gene alterations, rather than..."
States the single-spectrum conclusion from shared PRKD genotype across all four histologic categories.
Two-Entity (Pathogenetic Dichotomy) Model
prkd_pathogenetic_dichotomy ALTERNATIVE
Evidence balance 2 support
Classic PAC and cribriform adenocarcinoma are distinct entities that happen to involve the same gene family: the near-restriction of rearrangements to cribriform tumors and of the hotspot mutation to classic tumors, combined with their different primary sites and sharply different nodal metastasis rates, is read as a pathogenetic dichotomy rather than intra-entity variation. The original rearrangement study raised exactly this reading, and the naming change that folded cribriform adenocarcinoma into PAC was contested on the grounds of these clinical behaviour differences. The disagreement is unresolved and is not merely nomenclatural, because nodal risk drives whether neck dissection is considered.
Show evidence (2 references)
PMID:24942367 SUPPORT Human Clinical
"Controversy exists as to whether these tumors represent separate entities or variants of one spectrum, as they appear to have significant overlap, but also clinicopathologic differences."
Frames the two-entity question as genuinely open, supporting ALTERNATIVE status for this model.
PMID:29761209 SUPPORT Human Clinical
"This approach raised controversy, predominantly because of possible differences in clinical behaviour."
Documents that the WHO decision to group cribriform adenocarcinoma under PAC was contested specifically on clinical behaviour grounds.
?

Discussions and Knowledge Gaps

5
What drives the substantial minority of polymorphous adenocarcinomas that carry neither the PRKD1 hotspot mutation nor a PRKD1/2/3 rearrangement?
KNOWLEDGE GAP OPEN pac_prkd_wildtype_driver_gap
Attached to
pathophysiology#Deregulated Protein Kinase D Signaling
Roughly one fifth of tumors across the PAC spectrum have no detectable PRKD alteration, and the obvious candidate explanation has been actively excluded: kinase domain sequencing of PRKD2 and PRKD3 in PRKD1-wild-type classic tumors found no mutations. Whether these cases are driven by non-hotspot PRKD1 lesions, by cryptic rearrangements missed by break-apart FISH, by epigenetic activation of the same pathway, or by a genuinely different mechanism is unresolved. This matters for the convergence claim in this entry: if the wild-type cases are driven by something other than protein kinase D, then PAC is not a single-pathway disease.
Proposed experiments
Whole-genome and RNA sequencing of PRKD-wild-type PAC
exp_pac_wgs_rnaseq_prkd_wildtype
Apply whole-genome and RNA sequencing to tumors lacking both the PRKD1 hotspot mutation and PRKD1/2/3 rearrangements, which prior studies could not do for want of frozen material, to detect non-hotspot PRKD1 variants, cryptic fusions, and alternative drivers.
Direct protein kinase D pathway activity readout across genotypes
exp_pac_pathway_activity_readout
Measure protein kinase D substrate phosphorylation in hotspot-mutant, fusion-positive, and wild-type tumors to test whether wild-type cases nonetheless show pathway activation, which would support convergence by a non-genetic route.
Show evidence (2 references)
PMID:31492931 SUPPORT Human Clinical
"We did not identify genetic alterations in PRKD genes in 21.6% (n=7) of the cases studied."
Quantifies the PRKD-wild-type fraction that constitutes this gap.
PMID:26426580 SUPPORT Human Clinical
"Further studies are warranted to define the driver genetic events"
The study that excluded PRKD2/PRKD3 kinase domain mutations explicitly leaves the driver of these cases undefined.
Should cribriform adenocarcinoma of salivary gland be curated as a subtype of polymorphous adenocarcinoma or as a separate disease entity?
CONTROVERSY OPEN pac_casg_entity_boundary
Attached to
pathophysiology#Regional Lymph Node Metastasis
This entry follows the WHO classification and NCIT in modeling cribriform adenocarcinoma as a subtype, and records the competing reading as an ALTERNATIVE mechanistic hypothesis rather than silently resolving it. The disagreement is empirically grounded on both sides: shared PRKD genotype and a continuum of indeterminate cases favour one spectrum, while different primary site, different lesion class, and a roughly ten-fold difference in nodal metastasis rate favour two entities. It is also not purely academic, because nodal risk determines whether neck dissection is considered. Should dismech later split these into separate Disease entries, the natural structure would be two entries plus a Grouping with SHARED_PATHWAY basis.
Show evidence (3 references)
PMID:29761209 SUPPORT Human Clinical
"Previously, PAC was referred to as polymorphous low-grade adenocarcinoma (PLGA), but the new WHO classification of salivary gland tumours has also included under the PAC subheading, the so-called cribriform adenocarcinoma of minor salivary glands (CAMSG)."
Documents the WHO decision this entry follows in treating cribriform adenocarcinoma as a subtype.
PMID:34023291 SUPPORT Human Clinical
"Recently, histologic grade was removed from salivary tumor nomenclature by the WHO to include disease of higher grade."
Explains why "low-grade" was dropped from the name: the entity as now defined admits higher-grade disease, which is the same widening that brought cribriform adenocarcinoma under the PAC heading.
PMID:34023291 SUPPORT Human Clinical
"One such entity, cribriform adenocarcinoma (CAC), is an aggressive group of polymorphous adenocarcinoma (PAC), with frequent nodal metastasis and locoregional recurrence."
Characterises cribriform adenocarcinoma as an aggressive group within PAC; counted as PARTIAL because the source adopts the subtype reading rather than adjudicating between the one-entity and two-entity models.
Do PRKD alterations carry independent prognostic information, or are they only diagnostic and subtype-defining markers?
KNOWLEDGE GAP OPEN pac_prkd_prognostic_significance
Attached to
pathophysiology#Regional Lymph Node Metastasis
Fusion status correlates strongly with nodal metastasis, yet recurrence-free survival did not differ between fusion-positive and mutation-positive tumors in the cohort where that comparison was made, and the authors attribute this to limited power given how rare recurrence is. A recent systematic review concludes that the prognostic significance of PRKD alterations remains inconclusive while their diagnostic value is established. Because tumor-related death is essentially absent, any prognostic endpoint must be regional control or recurrence rather than survival, which makes adequately powered studies difficult.
Proposed experiments
Multicentre genotype-stratified outcome study with regional-control endpoints
exp_pac_multicentre_genotype_outcome
Pool genotyped PAC-spectrum cases across centres with sufficient follow-up to test whether PRKD lesion class predicts regional recurrence and nodal relapse independently of histologic subtype and papillary proportion.
Show evidence (2 references)
PMID:42438055 SUPPORT Human Clinical
"PRKD alterations serve primarily as diagnostic markers, and their prognostic significance remains inconclusive."
A systematic review states directly that the prognostic role is unresolved while the diagnostic role is established.
PMID:31492931 SUPPORT Human Clinical
"our study may have a limited statistical power to assess the prognostic significance of PRKD1 E710D hotspot mutations or PRKD1/2/3 rearrangements in predicting clinical outcomes"
The authors explicitly identify limited power as the reason the prognostic question is unresolved.
Why is there no experimental model of polymorphous adenocarcinoma, and what would one have to reproduce to be useful?
KNOWLEDGE GAP OPEN pac_no_model_systems_gap
Attached to
pathophysiology#Deregulated Protein Kinase D Signaling pathophysiology#Architecturally Polymorphous Infiltrative Growth
This entry carries no experimental_models, animal_models, or computational_models, and that is a statement about the field rather than an omission in curation: no established cell line, organoid, or genetically engineered animal model of PAC is in routine use. The consequence is visible in the pathograph itself — the step from protein kinase D activation to the tumor's characteristic multipattern architecture is INDIRECT_UNKNOWN_INTERMEDIATES precisely because there is no system in which to interrogate it. Even primary material is scarce: the study that defined the PRKD-wild-type subset could not pursue it for want of frozen tissue. A useful model would need to reproduce the defining dissociation of architectural diversity from cytological uniformity, not merely express the mutant kinase.
Proposed experiments
PRKD1 E710D knock-in salivary gland organoids
exp_pac_e710d_salivary_organoid
Introduce the E710D hotspot substitution into human salivary gland epithelial organoids and test whether activated protein kinase D alone produces multipattern architecture with retained cytological uniformity, or whether additional context is required.
Side-by-side fusion versus hotspot models of nodal propensity
exp_pac_fusion_vs_hotspot_comparison
Build matched models carrying a PRKD fusion and the PRKD1 hotspot mutation and compare invasive and lymphatic behaviour, to test whether the 50% versus 0% nodal metastasis difference is intrinsic to the lesion class rather than a correlate of tumor site.
Conditional salivary-epithelial Prkd1 E710D knock-in mouse
exp_pac_conditional_knockin_mouse
Restrict expression of the activating allele to salivary gland epithelium to test whether a whole-organism model develops an indolent, neurotropic palatal tumor resembling human PAC.
Show evidence (1 reference)
PMID:31492931 SUPPORT Human Clinical
"regrettably, representative frozen samples from these PRKD1/2/3 wild-type tumors were unavailable"
Documents that even primary tissue is limiting for mechanistic follow-up in this tumor; PARTIAL because it evidences scarcity of material rather than the absence of model systems as such, which is an absence no single publication asserts.
MONDO lacks a class for polymorphous adenocarcinoma, so what should anchor disease_term?
CURATION TODO OPEN pac_mondo_term_gap
Searching MONDO labels and exact synonyms returns no polymorphous adenocarcinoma class, and no MONDO term cross-references NCIT:C35702 or its parent NCIT:C8021 (Salivary Gland Adenocarcinoma). disease_term is therefore anchored to the nearest MONDO superclass, salivary gland carcinoma (MONDO:0000521), with exact identity carried in ncit_mappings as skos:exactMatch. This is a deliberate broadMatch-by-necessity, not an assertion of equivalence between PAC and salivary gland carcinoma. A MONDO term request for polymorphous adenocarcinoma, with the two NCIT subtypes, would let disease_term be tightened.
Show evidence (1 reference)
PMID:29266837 SUPPORT Human Clinical
"PAC demonstrates cytological overlap with 2 other salivary gland tumors frequently encountered in the same location, namely ACC and pleomorphic adenoma (PA)."
Establishes that PAC is a distinct entity requiring separation from named mimics, which is why a dedicated ontology class is warranted rather than reliance on a broad parent.
⚙

Pathophysiology

6
PRKD1 Hotspot Activating Mutation
A recurrent somatic missense mutation in PRKD1 encoding p.Glu710Asp occurs in the catalytic kinase domain of protein kinase D1 and is present in the majority of conventional polymorphous adenocarcinomas. Functional work showed the substitution is kinase-activating and behaves as a driver. The mutation is essentially absent from other salivary gland tumor types, making it both the initiating lesion and the most specific molecular diagnostic marker for this entity.
PRKD1 hgnc:9407 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves PRKD1 (hgnc:9407). hgnc:9407 is a gene from the HUGO Gene Nomenclature Committee.
protein serine/threonine kinase activity GO:0004674 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves increased protein serine/threonine kinase activity (GO:0004674). GO:0004674 is a molecular function from the Gene Ontology. ↑ INCREASED
Downstream
Deregulated Protein Kinase D Signaling The activating substitution raises protein kinase D1 catalytic output, producing constitutive signaling through the pathway.
Show evidence (2 references)
PMID:25240283 SUPPORT Human Clinical
"We identified PRKD1 hotspot mutations encoding p.Glu710Asp in 72.9% of PLGAs but not in other salivary gland tumors."
The originating study establishes both the hotspot identity and its restriction to this tumor type among salivary gland neoplasms.
PMID:25240283 SUPPORT In Vitro
"Functional studies demonstrated that this kinase-activating alteration likely constitutes a driver of PLGA."
Functional assays support the mutation being kinase-activating and a driver rather than a passenger, justifying the INCREASED modifier on kinase activity.
PRKD Family Gene Rearrangement
Rearrangements involving PRKD1, PRKD2, or PRKD3 generate fusion genes that place a PRKD kinase domain under new regulatory control. First identified as ARID1A-PRKD1 and DDX3X-PRKD1 fusions in cribriform adenocarcinoma, the partner repertoire is unusually diverse for a salivary gland malignancy, with ARID1A and ARID1B the most common partners. These rearrangements are the characteristic driver of the cribriform subtype and are mutually exclusive with the PRKD1 hotspot mutation, representing a parallel route to the same deregulated kinase output.
PRKD1 hgnc:9407 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves PRKD1 (hgnc:9407). hgnc:9407 is a gene from the HUGO Gene Nomenclature Committee. PRKD2 hgnc:17293 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves PRKD2 (hgnc:17293). hgnc:17293 is a gene from the HUGO Gene Nomenclature Committee. PRKD3 hgnc:9408 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves PRKD3 (hgnc:9408). hgnc:9408 is a gene from the HUGO Gene Nomenclature Committee. ARID1A hgnc:11110 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ARID1A (hgnc:11110). hgnc:11110 is a gene from the HUGO Gene Nomenclature Committee. ARID1B hgnc:18040 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves ARID1B (hgnc:18040). hgnc:18040 is a gene from the HUGO Gene Nomenclature Committee. DDX3X hgnc:2745 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves DDX3X (hgnc:2745). hgnc:2745 is a gene from the HUGO Gene Nomenclature Committee.
Downstream
Deregulated Protein Kinase D Signaling PRKD fusion proteins place a kinase domain under new regulatory control, converging on the same constitutive protein kinase D signaling output as the hotspot mutation.
Show evidence (4 references)
PMID:24942367 SUPPORT Human Clinical
"The RNAseq of 2 CAMSGs showed ARID1A-PRKD1 and DDX3X-PRKD1 fusions, respectively, while no fusion candidates were identified in two PLGAs."
The originating study identifies the first two PRKD1 fusion partners and the enrichment of fusions in cribriform rather than classic tumors.
PMID:24942367 SUPPORT Human Clinical
"Six additional cases each showed PRKD2 and PRKD3 rearrangements."
Extends the rearrangement spectrum from PRKD1 to the paralogues PRKD2 and PRKD3, supporting a gene-family rather than single-gene lesion.
PMID:37595638 SUPPORT Human Clinical
"The most common partners for the PRKD genes were ARID1A and ARID1B."
Next-generation sequencing of 51 cases identifies ARID1A and ARID1B as the predominant fusion partners.
+ 1 more reference
Deregulated Protein Kinase D Signaling
Both driver classes converge on deregulated protein kinase D activity in the neoplastic ductal epithelium. The PRKD kinases are diacylglycerol-activated serine/threonine kinases acting in the diacylglycerol and protein kinase C signal transduction pathway, and the shared membership of PRKD1, PRKD2, and PRKD3 in that pathway is what makes lesions in any of the three interchangeable drivers. Genetic alterations targeting PRKD genes are present in roughly four fifths of tumors across the PAC histologic spectrum, supporting a convergent phenotype driven by one pathway.
salivary gland cell CL:0009005 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves salivary gland cell (CL:0009005). CL:0009005 is a cell type from the Cell Ontology.
protein kinase C signaling GO:0070528 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased protein kinase C signaling (GO:0070528). GO:0070528 is a biological process from the Gene Ontology. ↑ INCREASED positive regulation of cell population proliferation GO:0008284 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased positive regulation of cell population proliferation (GO:0008284). GO:0008284 is a biological process from the Gene Ontology. ↑ INCREASED
Downstream
Architecturally Polymorphous Infiltrative Growth Constitutive protein kinase D signaling in ductal epithelium drives the proliferation and infiltrative growth that produce the tumor's characteristic multipattern architecture.
Show evidence (2 references)
PMID:24942367 SUPPORT Human Clinical
"As PRKD2 and PRKD3 share similar functions with PRKD1 in the diacylglycerol and protein kinase C signal transduction pathway, we expanded the investigation for these genes by FISH."
Names the shared pathway that makes PRKD1, PRKD2, and PRKD3 lesions interchangeable drivers, which is the rationale for this convergence node.
PMID:31492931 SUPPORT Human Clinical
"We identified genetic alterations targeting PRKD genes in the majority (78.4%) of tumors in the histologic spectrum of polymorphous adenocarcinoma included in this study."
Quantifies PRKD pathway involvement across the histologic spectrum, supporting convergence on this node.
Architecturally Polymorphous Infiltrative Growth
The transformed cells form a single tumor displaying multiple coexisting architectural patterns (tubular, trabecular, cribriform, papillary, solid, single-file) while remaining cytologically bland and uniform, and infiltrate surrounding tissue with an unencapsulated advancing border. The dissociation of architectural variability from cytological uniformity is the defining morphological property of the entity and the origin of the name.
salivary gland cell CL:0009005 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves salivary gland cell (CL:0009005). CL:0009005 is a cell type from the Cell Ontology.
Downstream
Perineural Invasion Infiltrative growth extends into perineural spaces, where the tumor forms characteristic concentric cuffs around nerve fascicles.
Regional Lymph Node Metastasis Invasive growth permits lymphatic spread to cervical nodes, a step strongly conditioned by which PRKD lesion class is present.
Perineural Invasion
Tumor cells stream circumferentially around small nerves in concentric, targetoid whorls. Neurotropism is frequent, yet in the largest published series it coexisted with excellent long-term outcome after surgical excision alone.
Show evidence (2 references)
PMID:10421256 SUPPORT Human Clinical
"The tumors were infiltrative and characterized by a polymorphous growth pattern, with individual tumors demonstrating multiple patterns, including solid, ductotubular, cribriform, trabecular, and single file growth. Neurotropism was identified frequently."
The largest published series reports frequent neurotropism, supporting perineural invasion as a characteristic feature.
PMID:10421256 SUPPORT Human Clinical
"At an average of 115.4 months after presentation, approximately 97.6% of all patients were either alive or had died without evidence of recurrent disease after treatment with surgical excision only."
Establishes excellent long-term outcome in the same cohort in which neurotropism was frequent. PARTIAL because the series does not analyse perineural invasion as an independent prognostic variable, so this bounds rather than proves the claim that it is not adverse here.
Regional Lymph Node Metastasis
Spread to cervical lymph nodes is the principal clinically actionable difference within the entity. Fusion-positive tumors metastasized to nodes in 50% of cases at primary resection whereas hotspot-mutation-positive tumors did so in none, and pooled review data show nodal metastasis in about half of cribriform tumors against a much lower rate across PAC as a whole. This is why subtype and genotype assignment carries surgical consequences for neck management.
Show evidence (2 references)
PMID:31492931 SUPPORT Human Clinical
"Among the 37 tested tumors, 9 (24%) were associated with nodal metastasis at the time of primary resection, including 8 of 16 (50%) fusion-positive tumors, 0 of 14 (0%) mutation-positive tumors"
Directly quantifies the genotype-conditioned difference in nodal metastasis that this node records.
PMID:34023291 SUPPORT Human Clinical
"there was an increased incidence of nodal metastasis in CAC (53%) as compared with that in PAC of all subtypes"
A systematic review independently corroborates the elevated nodal metastasis rate of the cribriform subtype.
✶

Histopathology

9
Cytological Uniformity with Architectural Diversity
The defining feature: multiple architectural patterns coexist within one tumor while the individual cells remain bland, small to medium sized, and monomorphic. Diagnosis rests on recognising this dissociation, since no single pattern is specific.
Show evidence (1 reference)
PMID:35507302 SUPPORT Human Clinical
"Because of its architectural diversity, histological diagnosis of PAC can be difficult especially for small biopsies, and immunohistochemistry is of great help in differentiating it from its histologic mimics."
Confirms that architectural diversity is the defining and diagnostically problematic feature, and the reason immunohistochemistry is needed on small biopsies.
Cribriform Pattern
Sieve-like arrangement of tumor cells. Prominent and multinodular in the cribriform subtype, from which it takes its name, but also present focally in conventional tumors; notably, the measured proportion of cribriform area does not by itself predict the underlying PRKD lesion.
Tubular Pattern
Small ducts and tubules lined by uniform cells, a common component of conventional PAC.
Trabecular Pattern
Cords and trabeculae of tumor cells, frequently including single-file streaming, which is more characteristic of hotspot-mutant tumors than of fusion-positive ones.
Papillary Growth Pattern
Papillary and papillary-cystic architecture. Papillary growth is significantly more common in fusion-positive tumors and has been associated with worse outcome, which is the basis for recommending that the percentage of papillae be reported.
Show evidence (1 reference)
PMID:31492931 SUPPORT Human Clinical
"Such evidence suggests that the percentage of papillae may be predictive of the underlying genetic alteration in PRKD genes as well as the clinical outcome."
Links papillary proportion to both PRKD genotype and outcome, supporting the reporting recommendation.
Solid Growth Pattern
Sheets of uniform cells without duct formation, one of the coexisting patterns of conventional PAC.
Multinodular Pattern
Multiple discrete tumor nodules, a feature of the cribriform subtype.
Perineural Invasion FREQUENT
Concentric, targetoid cuffing of small nerves by tumor. Frequent enough to be a useful diagnostic clue, though it is shared with adenoid cystic carcinoma and so does not discriminate between them on its own.
Show evidence (1 reference)
PMID:10421256 SUPPORT Human Clinical
"The tumors were infiltrative and characterized by a polymorphous growth pattern, with individual tumors demonstrating multiple patterns, including solid, ductotubular, cribriform, trabecular, and single file growth. Neurotropism was identified frequently."
Supports the FREQUENT frequency band for perineural invasion in a 164-case series.
Absence of a Distinct Myoepithelial Component
PAC lacks the true dual luminal/myoepithelial population of adenoid cystic carcinoma and pleomorphic adenoma. This underpins the p63-positive but p40-negative immunophenotype, because p40 recognises a p63 isoform specific for true myoepithelial differentiation.
Show evidence (1 reference)
PMID:24969705 SUPPORT Human Clinical
"PLGAs do not harbor a myoepithelial component"
States the absence of a myoepithelial component, which is the mechanistic basis for the discriminating p63+/p40- pattern.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Salivary Gland Polymorphous Adenocarcinoma Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

5
Cardiovascular 1
Cervical Lymphadenopathy from Nodal Metastasis HP:0025289 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Cervical lymph node metastasis, annotated with Cervical lymphadenopathy (HP:0025289). HP:0025289 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29761209 SUPPORT Human Clinical
"PLGA (PAC, classical variant) only rarely metastasizes, whereas CAMSG often shows metastases to the neck lymph nodes."
Contrasts the rare metastasis of classical PAC with frequent neck nodal metastasis in the cribriform subtype, supporting the subtype restriction on this phenotype.
Other 4
Palatal Mass FREQUENT Palate neoplasm HP:0031366 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Palatal mass, annotated with Palate neoplasm (HP:0031366), qualified as course progressive. HP:0031366 is a phenotype from the Human Phenotype Ontology.
Course: PROGRESSIVE
Show evidence (3 references)
PMID:42438055 SUPPORT Human Clinical
"Clinicopathological findings show that the tumor is most common in women and on the palate."
A systematic review identifies the palate as the most common site, supporting a FREQUENT frequency band for palatal presentation.
PMID:31492931 SUPPORT Human Clinical
"mutation-positive tumors most frequently originated from the palate (10/14, 71%) and rarely occurred in base of tongue (1/14, 7%)"
Quantifies palatal origin in 71% of hotspot-mutant tumors, supporting the FREQUENT band for the conventional subtype.
PMID:10421256 SUPPORT Human Clinical
"The patients usually presented clinically with a palatal mass"
A 164-case series reports palatal mass as the usual presentation, independently supporting the FREQUENT band.
Salivary Gland Neoplasm HP:0100684 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Salivary gland neoplasm (HP:0100684). HP:0100684 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:31492931 SUPPORT Human Clinical
"The majority (95%; 35/37) of tumors originated in minor salivary glands, with the palate being the most frequent site of origin for all tumor types"
Confirms salivary gland origin with minor gland predominance.
Neoplasm of the Oral Cavity HP:0100649 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Neoplasm of the oral cavity (HP:0100649). HP:0100649 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:29266837 SUPPORT Human Clinical
"is the second most common intraoral malignant salivary gland carcinoma after adenoid cystic carcinoma (ACC) and carries an excellent prognosis."
Establishes the intraoral location and the ranking among intraoral salivary malignancies.
Neoplasm of the Tongue HP:0100648 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Base of tongue neoplasm, annotated with Neoplasm of the tongue (HP:0100648). HP:0100648 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:34023291 SUPPORT Human Clinical
"CAC occurs most frequently in the tongue and PAC in the palate."
Directly supports the tongue predilection of the cribriform subtype.
🧬

Genetic Associations

5
PRKD1
Gene: PRKD1 hgnc:9407 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is PRKD1 (hgnc:9407). hgnc:9407 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (1 reference)
PMID:31492931 SUPPORT Human Clinical
"In agreement with previous reports, PRKD1 E710D hotspot mutations were mutually exclusive with rearrangements in PRKD1/2/3"
Supports the two PRKD1 lesion classes being alternative rather than cooperating events in the same tumor.
PRKD2
Gene: PRKD2 hgnc:17293 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is PRKD2 (hgnc:17293). hgnc:17293 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (2 references)
PMID:24942367 SUPPORT Human Clinical
"Six additional cases each showed PRKD2 and PRKD3 rearrangements."
Documents PRKD2 rearrangement as a recurrent lesion in this tumor family.
PMID:26426580 SUPPORT Human Clinical
"PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements are unlikely to harbour somatic mutations in the kinase domains of PRKD2 or PRKD3."
Establishes that PRKD2 involvement is via rearrangement, not kinase domain point mutation.
PRKD3
Gene: PRKD3 hgnc:9408 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is PRKD3 (hgnc:9408). hgnc:9408 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: SOMATIC_DRIVER variant_origin: SOMATIC
Show evidence (1 reference)
PMID:24942367 SUPPORT Human Clinical
"As PRKD2 and PRKD3 share similar functions with PRKD1 in the diacylglycerol and protein kinase C signal transduction pathway, we expanded the investigation for these genes by FISH."
Gives the pathway rationale for PRKD3 being an interchangeable driver.
ARID1A
Gene: ARID1A hgnc:11110 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is ARID1A (hgnc:11110). hgnc:11110 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: COOPERATING variant_origin: SOMATIC
Show evidence (1 reference)
PMID:37595638 SUPPORT Human Clinical
"The most common partners for the PRKD genes were ARID1A and ARID1B."
Identifies ARID1A among the two most common PRKD fusion partners.
DDX3X
Gene: DDX3X hgnc:2745 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is DDX3X (hgnc:2745). hgnc:2745 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: COOPERATING variant_origin: SOMATIC
Show evidence (1 reference)
PMID:24942367 SUPPORT Human Clinical
"The RNAseq of 2 CAMSGs showed ARID1A-PRKD1 and DDX3X-PRKD1 fusions, respectively, while no fusion candidates were identified in two PLGAs."
Documents DDX3X-PRKD1 as one of the two founding fusions of this entity.
💊

Medical Actions

3
Wide Surgical Excision
Action: surgical procedureNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is surgical procedure (NCIT:C15329). NCIT:C15329 is a clinical intervention from the NCI Thesaurus. Ontology label: Surgical Procedure NCIT:C15329
Complete surgical excision with clear margins is the mainstay of treatment and is usually definitive: in the largest series, treatment with excision alone left about 97.6% of patients alive or dead without disease at an average of 115 months. Sources differ on how wide is wide enough — one review specifies wide excision, while the 164-case series recommends conservative but complete excision — so the shared commitment is completeness of removal rather than a particular margin width.
Mechanism Target:
INHIBITS Architecturally Polymorphous Infiltrative Growth — Resection with clear margins removes the infiltrative tumor mass; the unencapsulated advancing border is the reason wide rather than enucleating excision is required.
Show evidence (3 references)
PMID:29761209 SUPPORT Human Clinical
"The optimal treatment comprises wide surgical excision, often with adjuvant radiotherapy. In general, PAC has a good prognosis."
Establishes wide surgical excision as the optimal primary treatment and the generally good prognosis.
PMID:10421256 SUPPORT Human Clinical
"Conservative but complete surgical excision is the treatment of choice for these slow-growing tumors with a low proliferation index; adjuvant therapy does not appear to alter the prognosis."
The largest series names complete surgical excision as the treatment of choice, and is the source of the conservative-versus-wide tension noted in the description.
PMID:10421256 SUPPORT Human Clinical
"At an average of 115.4 months after presentation, approximately 97.6% of all patients were either alive or had died without evidence of recurrent disease after treatment with surgical excision only."
Quantifies the durability of excision alone, supporting surgery as usually definitive.
Adjuvant Radiotherapy
Action: radiation therapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is radiation therapy (NCIT:C15313). NCIT:C15313 is a clinical intervention from the NCI Thesaurus. Ontology label: Radiation Therapy NCIT:C15313
Radiotherapy is used adjunctively, conventionally for adverse features such as positive or close margins or recurrent disease. Its benefit is not established: one systematic review reports resection with adjuvant radiotherapy as conventional and effective with no documented tumor-related deaths, but the 164-case series states directly that adjuvant therapy does not appear to alter the prognosis, and reports about 97.6% freedom from disease after excision alone. Against so high a surgical cure rate there is little room for an adjuvant effect to show, so this entry records radiotherapy as conventionally used rather than as demonstrated to improve outcome.
Show evidence (2 references)
PMID:42438055 SUPPORT Human Clinical
"Resection and adjuvant radiotherapy are the conventional and effective treatments, with no documented tumor-related deaths."
Supports resection plus adjuvant radiotherapy as the conventional effective approach and documents the absence of tumor-related deaths.
PMID:10421256 REFUTE Human Clinical
"Conservative but complete surgical excision is the treatment of choice for these slow-growing tumors with a low proliferation index; adjuvant therapy does not appear to alter the prognosis."
The largest series finds no prognostic benefit from adjuvant therapy, directly opposing the claim that adjuvant radiotherapy improves outcome; recorded as REFUTE so the disagreement is machine-visible rather than averaged away in prose.
Neck Dissection for Fusion-Positive or Cribriform Disease
Action: neck dissectionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is neck dissection (NCIT:C15643). NCIT:C15643 is a clinical intervention from the NCI Thesaurus. Ontology label: Neck Dissection NCIT:C15643
Regional lymph node dissection is considered when nodal risk is high, that is for cribriform-subtype or fusion-positive tumors, in which nodal metastasis is present in roughly half of cases at primary resection. This is the one place where subtype and genotype assignment changes surgical management, and it is the practical reason the one-entity versus two-entity question matters. Conventional hotspot-mutant palatal tumors do not warrant elective neck treatment on current evidence.
Mechanism Target:
INHIBITS Regional Lymph Node Metastasis — Neck dissection addresses established or high-risk regional nodal disease in the fusion-positive/cribriform group.
Show evidence (2 references)
PMID:31492931 SUPPORT Human Clinical
"Fusion-positive tumors, however, appear to be more aggressive clinically and may require additional treatments (e.g. neck dissection)."
Directly supports considering neck dissection specifically for fusion-positive tumors.
PMID:34023291 SUPPORT Human Clinical
"these tumors likely comprise a significant portion of the cases of PAC with poor outcomes and are deserving of attention and consideration for escalation in oncologic treatment."
Supports treatment escalation for the cribriform subgroup on the basis of its worse regional behaviour.
🔬

Biochemical Markers

5
PRKD1 E710D Hotspot Mutation Testing
Show evidence (2 references)
PMID:29266837 SUPPORT Human Clinical
"The specificity of the PRKD1 hotspot mutation for identifying PAC among ACC and PA cases was 100% whereas the sensitivity was 50%."
Quantifies both the perfect specificity and the limited sensitivity that govern how this test is used.
PMID:29266837 SUPPORT Human Clinical
"Alternative PRKD1 mutations exclude PAC, and are more suggestive of ACC."
Supports the requirement that interpretation be restricted to the hotspot rather than any PRKD1 variant.
PRKD1/2/3 Rearrangement Testing
Show evidence (2 references)
PMID:37595638 SUPPORT Human Clinical
"The wide variety of involved genes is unlike in other salivary gland malignancies and warrants a broader strategy of sequencing for molecular confirmation for particularly challenging cases, as our NGS study shows."
Supports preferring broad sequencing over break-apart FISH because of the unusually diverse partner repertoire.
PMID:31492931 SUPPORT Human Clinical
"molecular testing for PRKD1/2/3 fusion may be of clinical relevance pre-operatively to risk-stratify patients"
Supports the proposed preoperative use of fusion testing for nodal risk stratification.
p63-Positive, p40-Negative Immunophenotype
Show evidence (3 references)
PMID:24969705 SUPPORT Human Clinical
"All 11 PLGAs (100 %) were positive for p63 but completely negative for p40."
Documents the consistent discordant staining pattern in all PAC cases tested.
PMID:24969705 SUPPORT Human Clinical
"PLGA consistently exhibits a p63+/p40- immunophenotype that can help distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma"
States the diagnostic utility of the pattern against the two principal mimics.
PMID:35507302 SUPPORT Human Clinical
"Overall, > 90% positivity was observed for pan-cytokeratin (CK) (97.3%), CK7 (96.8%), CK7/8 (97.4%), E-cadherin (90.0%), Vimentin (92.5%), S100 (97.0%), p63 (91.7%), and SOX10 (100%), while little to no positivity was observed for CK20 (0.0%), p40 (0.0%), and GFAP (5.0%)."
A meta-analysis of 409 cases quantifies the discordant pattern at scale, with p63 positive in 91.7% and p40 positive in 0.0%, far exceeding the 11-case series above.
S100, CK7, and SOX10 Expression
Show evidence (2 references)
PMID:35507302 SUPPORT Human Clinical
"The results of this systematic review indicate that CK7+/CK20-, p63+/p40-, S100+, Vimentin+, and GFAP- immunophenotype have diagnostic value for PAC."
States the composite immunophenotype of diagnostic value, pooled across 32 studies and 409 cases.
PMID:42438055 SUPPORT Human Clinical
"CK7 and S100 IHC markers consistently test positive."
An independent systematic review corroborates consistent CK7 and S100 positivity.
Low Ki-67 (MIB-1) Proliferation Index
Show evidence (1 reference)
PMID:35507302 SUPPORT Human Clinical
"The average MIB-1 labeling index was 3.78%."
Quantifies the low proliferation index pooled across the meta-analysis cohort.
🔬

Diagnosis

4
Incisional biopsy
Diagnosis is established primarily on incisional biopsy of the lesion, ahead of definitive resection.
incisional biopsy NCIT:C15386 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:29761209 SUPPORT Human Clinical
"The diagnosis is mainly based on an incisional biopsy."
Identifies incisional biopsy as the principal diagnostic procedure.
Immunohistochemical panel
Immunohistochemistry is the main adjunct to morphology, and is most valuable on small biopsies where architectural diversity cannot be appreciated. The discriminating result is the discordant p63-positive/p40-negative pattern; the supporting profile is CK7-positive, CK20-negative, S100-positive, vimentin-positive, SOX10-positive, GFAP-negative, with a low Ki-67 index.
immunohistochemistry NCIT:C23020 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:35507302 SUPPORT Human Clinical
"Because of its architectural diversity, histological diagnosis of PAC can be difficult especially for small biopsies, and immunohistochemistry is of great help in differentiating it from its histologic mimics."
Establishes immunohistochemistry as the adjunct that resolves the small-biopsy problem created by architectural diversity.
PRKD1 hotspot sequencing
Targeted sequencing of the PRKD1 exon 15 hotspot can be run on fine-needle aspiration material as well as resection specimens. It is perfectly specific but only moderately sensitive, so it confirms rather than excludes, and only the hotspot substitution counts.
dideoxy chain termination DNA sequencing NCIT:C19641 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:29266837 SUPPORT Human Clinical
"The specificity of the PRKD1 hotspot mutation for identifying PAC among ACC and PA cases was 100% whereas the sensitivity was 50%."
Quantifies the confirm-but-do-not-exclude character of hotspot sequencing as a diagnostic test.
PRKD1/2/3 rearrangement testing
Break-apart FISH detects the fusion class but leaves partners unidentified and misses some fusions; RNA-based next-generation sequencing is preferable in difficult cases because the partner repertoire is unusually wide. Relevant beyond diagnosis because fusion status tracks nodal risk.
next generation sequencing NCIT:C101293 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:37595638 SUPPORT Human Clinical
"The wide variety of involved genes is unlike in other salivary gland malignancies and warrants a broader strategy of sequencing for molecular confirmation for particularly challenging cases, as our NGS study shows."
Supports preferring broad sequencing over break-apart FISH for molecular confirmation in challenging cases.
📈

Progression

2
Long-term outcome after treatment
Behavior is indolent. Pooled systematic-review data give recurrence of 12.5% for cribriform adenocarcinoma versus 17.8% for PAC overall, distant metastasis of 4.1% versus 5.5%, and death from disease of 3% versus 2.7% — that is, comparable between the two, with the difference concentrated in regional nodal spread rather than in distant spread or mortality. Note the disagreement between sources on mortality: one systematic review reports around 3% death from disease while another reports no documented tumor-related deaths, so disease-specific mortality should be treated as very low but not established as zero.
Show evidence (2 references)
PMID:34023291 SUPPORT Human Clinical
"The 2 groups show a similar biologic behavior in regards to incidence of distant metastasis (4.1 vs 5.5%), recurrence (12.5 vs 17.8%), and death from disease (3 vs 2.7%)."
Quantifies recurrence, distant metastasis, and disease-specific mortality and shows they are comparable between the cribriform subtype and PAC overall, isolating nodal spread as the real difference.
PMID:42438055 SUPPORT Human Clinical
"Resection and adjuvant radiotherapy are the conventional and effective treatments, with no documented tumor-related deaths."
A second systematic review reports no tumor-related deaths, which conflicts with the roughly 3% disease-specific mortality above; recorded as PARTIAL because the two pooled estimates disagree on this endpoint.
Follow-up in a genotyped PAC-spectrum cohort
In a centrally reviewed cohort followed for a median of 70 months, only three patients recurred and none died of disease, and recurrence-free survival did not differ between fusion-positive and hotspot-mutant tumors.
Show evidence (1 reference)
PMID:31492931 SUPPORT Human Clinical
"No death of disease was found during the follow-up period"
Documents absence of disease-specific death over extended follow-up in a genotyped cohort, consistent with indolent behaviour.
📊

Prevalence

2
Worldwide
Unknown Rare
PAC is consistently described as a rare tumor that is nonetheless the second most common malignancy of the minor salivary glands, after adenoid cystic carcinoma. The sources reviewed state rarity and rank qualitatively rather than reporting a quotable population rate, so only the coarse class is recorded. A registry-derived numeric incidence remains a curation gap.
Show evidence (2 references)
PMID:29761209 SUPPORT Human Clinical
"Although relatively rare, polymorphous adenocarcinoma (PAC) is likely the second most common malignancy of the minor salivary glands (MiSG)."
A dedicated review characterises PAC as relatively rare while ranking it second among minor salivary gland malignancies, supporting the qualitative RARE class without asserting a numeric rate.
PMID:25240283 SUPPORT Human Clinical
"Polymorphous low-grade adenocarcinoma (PLGA) is the second most frequent type of malignant tumor of the minor salivary glands."
Independently corroborates the second-most-frequent ranking among minor salivary gland malignancies under the former PLGA name.
Minor salivary gland PAC-spectrum cohort (37 tumors, central histopathologic review)
Unknown Unknown
Site and demographic distribution rather than an occurrence rate: 95% of PAC-spectrum tumors arose in minor salivary glands, the palate was the most frequent site for every histologic subtype, median age was 61 years, and there was a roughly 2:1 female predominance.
Show evidence (2 references)
PMID:31492931 SUPPORT Human Clinical
"The majority (95%; 35/37) of tumors originated in minor salivary glands, with the palate being the most frequent site of origin for all tumor types"
Quantifies the minor salivary gland and palatal predominance of the PAC spectrum in a centrally reviewed cohort.
PMID:31492931 SUPPORT Human Clinical
"The tumors affected 12 males (32%) and 25 (68%) females"
Documents the female predominance of the PAC spectrum in the same cohort.
{ }

Source YAML

click to show 
name: Salivary Gland Polymorphous Adenocarcinoma
creation_date: "2026-08-05T00:00:00Z"
category: Cancer
categories:
- Salivary Gland Cancer
- Rare Cancer
parents:
- salivary gland carcinoma
disease_term:
  preferred_term: polymorphous adenocarcinoma of salivary gland
  term:
    id: MONDO:0000521
    label: salivary gland carcinoma
mappings:
  ncit_mappings:
  - term:
      id: NCIT:C35702
      label: Salivary Gland Polymorphous Adenocarcinoma
    mapping_predicate: skos:exactMatch
    mapping_source: NCIT
    mapping_justification: >-
      NCIT is the only ontology in the dismech constrained set that codes this
      entity. MONDO has no polymorphous adenocarcinoma class (searched labels and
      exact synonyms), so disease_term is anchored to the nearest MONDO
      superclass, salivary gland carcinoma, and exact entity identity is carried
      here. The MONDO gap is recorded as an open discussion.
description: >-
  Polymorphous adenocarcinoma (PAC) is a low-grade malignant epithelial neoplasm
  of salivary gland origin with a striking predilection for the minor salivary
  glands of the palate. It is probably the second most common malignancy of the
  minor salivary glands, after adenoid cystic carcinoma (ACC). The name refers to
  architectural, not cytological, diversity: a single tumor displays tubular,
  trabecular, cribriform, papillary, solid, and single-file patterns and
  characteristically streams into concentric whorls around nerves, while the
  constituent cells remain bland and monomorphic. That combination of cytological
  uniformity with architectural variability is the diagnostic signature, and the
  basis for separating PAC from ACC and pleomorphic adenoma, which occupy the same
  anatomic site and overlap cytologically. Most conventional PAC is driven by a
  recurrent activating hotspot mutation in PRKD1 (p.Glu710Asp), while
  rearrangements of PRKD1, PRKD2, or PRKD3 characterize the cribriform subtype;
  the two lesion classes are mutually exclusive and converge on deregulated
  protein kinase D signaling, placing PAC among the tumors defined by a single
  pathway rather than a single mutation. Behavior is indolent, with frequent
  perineural invasion that does not carry the adverse prognostic weight it does in
  ACC, low rates of distant metastasis, and very low disease-specific mortality
  (pooled series report figures from around 3% down to none). The principal
  clinically actionable split within the entity is
  nodal risk: fusion-positive/cribriform tumors metastasize to neck nodes at a
  much higher rate than hotspot-mutant/classic tumors.
synonyms:
- PAC
- polymorphous adenocarcinoma
- polymorphous low-grade adenocarcinoma
- PLGA
- terminal duct adenocarcinoma
- PmA
classifications:
  icdo_morphology:
    classification_value: Carcinoma
  harrisons_chapter:
  - classification_value: ONCOLOGY_HEMATOLOGY
prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: RARE
  notes: >-
    PAC is consistently described as a rare tumor that is nonetheless the second
    most common malignancy of the minor salivary glands, after adenoid cystic
    carcinoma. The sources reviewed state rarity and rank qualitatively rather
    than reporting a quotable population rate, so only the coarse class is
    recorded. A registry-derived numeric incidence remains a curation gap.
  evidence:
  - reference: PMID:29761209
    reference_title: "Polymorphous adenocarcinoma of the salivary glands: reappraisal and update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Although relatively rare, polymorphous adenocarcinoma (PAC) is likely the
      second most common malignancy of the minor salivary glands (MiSG).
    explanation: >-
      A dedicated review characterises PAC as relatively rare while ranking it
      second among minor salivary gland malignancies, supporting the qualitative
      RARE class without asserting a numeric rate.
  - reference: PMID:25240283
    reference_title: "Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Polymorphous low-grade adenocarcinoma (PLGA) is the second most frequent
      type of malignant tumor of the minor salivary glands.
    explanation: >-
      Independently corroborates the second-most-frequent ranking among minor
      salivary gland malignancies under the former PLGA name.
- population: Minor salivary gland PAC-spectrum cohort (37 tumors, central histopathologic review)
  measure_type: UNKNOWN
  prevalence_class: UNKNOWN
  notes: >-
    Site and demographic distribution rather than an occurrence rate: 95% of
    PAC-spectrum tumors arose in minor salivary glands, the palate was the most
    frequent site for every histologic subtype, median age was 61 years, and there
    was a roughly 2:1 female predominance.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The majority (95%; 35/37) of tumors originated in minor salivary glands,
      with the palate being the most frequent site of origin for all tumor types
    explanation: >-
      Quantifies the minor salivary gland and palatal predominance of the
      PAC spectrum in a centrally reviewed cohort.
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The tumors affected 12 males (32%) and 25 (68%) females
    explanation: >-
      Documents the female predominance of the PAC spectrum in the same cohort.
progression:
- phase: Long-term outcome after treatment
  notes: >-
    Behavior is indolent. Pooled systematic-review data give recurrence of 12.5%
    for cribriform adenocarcinoma versus 17.8% for PAC overall, distant
    metastasis of 4.1% versus 5.5%, and death from disease of 3% versus 2.7% —
    that is, comparable between the two, with the difference concentrated in
    regional nodal spread rather than in distant spread or mortality. Note the
    disagreement between sources on mortality: one systematic review reports
    around 3% death from disease while another reports no documented
    tumor-related deaths, so disease-specific mortality should be treated as very
    low but not established as zero.
  evidence:
  - reference: PMID:34023291
    reference_title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The 2 groups show a similar biologic behavior in regards to incidence of
      distant metastasis (4.1 vs 5.5%), recurrence (12.5 vs 17.8%), and death
      from disease (3 vs 2.7%).
    explanation: >-
      Quantifies recurrence, distant metastasis, and disease-specific mortality
      and shows they are comparable between the cribriform subtype and PAC
      overall, isolating nodal spread as the real difference.
  - reference: PMID:42438055
    reference_title: "Polymorphous Adenocarcinoma and Cribriform Adenocarcinoma of Salivary Glands (Cribriform Subtype of PAC): PRKD Mutation, Diagnosis, and Prognosis-A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Resection and adjuvant radiotherapy are the conventional and effective
      treatments, with no documented tumor-related deaths.
    explanation: >-
      A second systematic review reports no tumor-related deaths, which conflicts
      with the roughly 3% disease-specific mortality above; recorded as PARTIAL
      because the two pooled estimates disagree on this endpoint.
- phase: Follow-up in a genotyped PAC-spectrum cohort
  notes: >-
    In a centrally reviewed cohort followed for a median of 70 months, only three
    patients recurred and none died of disease, and recurrence-free survival did
    not differ between fusion-positive and hotspot-mutant tumors.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      No death of disease was found during the follow-up period
    explanation: >-
      Documents absence of disease-specific death over extended follow-up in a
      genotyped cohort, consistent with indolent behaviour.
has_subtypes:
- name: Conventional
  display_name: Conventional (classic) polymorphous adenocarcinoma
  subtype_term:
    preferred_term: Salivary Gland Polymorphous Adenocarcinoma, Conventional Subtype
    term:
      id: NCIT:C201781
      label: Salivary Gland Polymorphous Adenocarcinoma, Conventional Subtype
  description: >-
    The classic form, overwhelmingly palatal, showing tubular, trabecular,
    microcystic, solid, and papillary-cystic architecture with mucinous, myxoid,
    or hyalinized stroma and frequent perineural involvement. It is the subtype
    enriched for the PRKD1 p.Glu710Asp hotspot mutation and rarely involves
    regional lymph nodes.
  genes:
  - preferred_term: PRKD1
    term:
      id: hgnc:9407
      label: PRKD1
  evidence:
  - reference: PMID:37595638
    reference_title: "Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      While conventional PACs are most associated with PRKD1 p.E710D hotspot
      mutations, the cribriform subtype is often associated with gene fusions in
      PRKD1, PRKD2, or PRKD3.
    explanation: >-
      States the genotype split between the conventional and cribriform subtypes
      that defines this subtype division.
- name: Cribriform
  display_name: Cribriform subtype (cribriform adenocarcinoma of salivary gland, CASG)
  subtype_term:
    preferred_term: Salivary Gland Polymorphous Adenocarcinoma, Cribriform Subtype
    term:
      id: NCIT:C201786
      label: Salivary Gland Polymorphous Adenocarcinoma, Cribriform Subtype
  description: >-
    A subtype with predominantly cribriform and multinodular architecture, a
    predilection for the base of tongue rather than the palate, and a markedly
    higher rate of regional lymph node metastasis at presentation. It is enriched
    for PRKD1/PRKD2/PRKD3 rearrangements rather than the PRKD1 hotspot mutation.
    Whether it is a subtype of PAC or a separate entity remains contested; the WHO
    classification places it under the PAC heading.
  genes:
  - preferred_term: PRKD1
    term:
      id: hgnc:9407
      label: PRKD1
  - preferred_term: PRKD2
    term:
      id: hgnc:17293
      label: PRKD2
  - preferred_term: PRKD3
    term:
      id: hgnc:9408
      label: PRKD3
  evidence:
  - reference: PMID:34023291
    reference_title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PAC and CAC both show median age of diagnosis in the sixth decade of life
      and a female predominance. CAC occurs most frequently in the tongue and PAC
      in the palate.
    explanation: >-
      Establishes the site difference (tongue versus palate) that distinguishes
      the cribriform subtype from conventional PAC.
pathophysiology:
- name: PRKD1 Hotspot Activating Mutation
  biological_scale: MOLECULAR
  description: >-
    A recurrent somatic missense mutation in PRKD1 encoding p.Glu710Asp occurs in
    the catalytic kinase domain of protein kinase D1 and is present in the
    majority of conventional polymorphous adenocarcinomas. Functional work showed
    the substitution is kinase-activating and behaves as a driver. The mutation is
    essentially absent from other salivary gland tumor types, making it both the
    initiating lesion and the most specific molecular diagnostic marker for this
    entity.
  genes:
  - preferred_term: PRKD1
    term:
      id: hgnc:9407
      label: PRKD1
  molecular_functions:
  - preferred_term: protein serine/threonine kinase activity
    term:
      id: GO:0004674
      label: protein serine/threonine kinase activity
    modifier: INCREASED
  evidence:
  - reference: PMID:25240283
    reference_title: "Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified PRKD1 hotspot mutations encoding p.Glu710Asp in 72.9% of PLGAs
      but not in other salivary gland tumors.
    explanation: >-
      The originating study establishes both the hotspot identity and its
      restriction to this tumor type among salivary gland neoplasms.
  - reference: PMID:25240283
    reference_title: "Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Functional studies demonstrated that this kinase-activating alteration
      likely constitutes a driver of PLGA.
    explanation: >-
      Functional assays support the mutation being kinase-activating and a driver
      rather than a passenger, justifying the INCREASED modifier on kinase
      activity.
  downstream:
  - target: Deregulated Protein Kinase D Signaling
    description: >-
      The activating substitution raises protein kinase D1 catalytic output,
      producing constitutive signaling through the pathway.
    causal_link_type: DIRECT
- name: PRKD Family Gene Rearrangement
  biological_scale: MOLECULAR
  description: >-
    Rearrangements involving PRKD1, PRKD2, or PRKD3 generate fusion genes that
    place a PRKD kinase domain under new regulatory control. First identified as
    ARID1A-PRKD1 and DDX3X-PRKD1 fusions in cribriform adenocarcinoma, the
    partner repertoire is unusually diverse for a salivary gland malignancy, with
    ARID1A and ARID1B the most common partners. These rearrangements are the
    characteristic driver of the cribriform subtype and are mutually exclusive
    with the PRKD1 hotspot mutation, representing a parallel route to the same
    deregulated kinase output.
  genes:
  - preferred_term: PRKD1
    term:
      id: hgnc:9407
      label: PRKD1
  - preferred_term: PRKD2
    term:
      id: hgnc:17293
      label: PRKD2
  - preferred_term: PRKD3
    term:
      id: hgnc:9408
      label: PRKD3
  - preferred_term: ARID1A
    term:
      id: hgnc:11110
      label: ARID1A
  - preferred_term: ARID1B
    term:
      id: hgnc:18040
      label: ARID1B
  - preferred_term: DDX3X
    term:
      id: hgnc:2745
      label: DDX3X
  evidence:
  - reference: PMID:24942367
    reference_title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The RNAseq of 2 CAMSGs showed ARID1A-PRKD1 and DDX3X-PRKD1 fusions,
      respectively, while no fusion candidates were identified in two PLGAs.
    explanation: >-
      The originating study identifies the first two PRKD1 fusion partners and
      the enrichment of fusions in cribriform rather than classic tumors.
  - reference: PMID:24942367
    reference_title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Six additional cases each showed PRKD2 and PRKD3 rearrangements.
    explanation: >-
      Extends the rearrangement spectrum from PRKD1 to the paralogues PRKD2 and
      PRKD3, supporting a gene-family rather than single-gene lesion.
  - reference: PMID:37595638
    reference_title: "Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common partners for the PRKD genes were ARID1A and ARID1B.
    explanation: >-
      Next-generation sequencing of 51 cases identifies ARID1A and ARID1B as the
      predominant fusion partners.
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In agreement with previous reports, PRKD1 E710D hotspot mutations were
      mutually exclusive with rearrangements in PRKD1/2/3
    explanation: >-
      Establishes mutual exclusivity of the two driver classes, supporting them as
      parallel routes to one pathway rather than cooperating lesions.
  downstream:
  - target: Deregulated Protein Kinase D Signaling
    description: >-
      PRKD fusion proteins place a kinase domain under new regulatory control,
      converging on the same constitutive protein kinase D signaling output as the
      hotspot mutation.
    causal_link_type: DIRECT
- name: Deregulated Protein Kinase D Signaling
  biological_scale: CELLULAR
  description: >-
    Both driver classes converge on deregulated protein kinase D activity in the
    neoplastic ductal epithelium. The PRKD kinases are diacylglycerol-activated
    serine/threonine kinases acting in the diacylglycerol and protein kinase C
    signal transduction pathway, and the shared membership of PRKD1, PRKD2, and
    PRKD3 in that pathway is what makes lesions in any of the three
    interchangeable drivers. Genetic alterations targeting PRKD genes are present
    in roughly four fifths of tumors across the PAC histologic spectrum,
    supporting a convergent phenotype driven by one pathway.
  cell_types:
  - preferred_term: salivary gland cell
    term:
      id: CL:0009005
      label: salivary gland cell
  biological_processes:
  - preferred_term: protein kinase C signaling
    term:
      id: GO:0070528
      label: protein kinase C signaling
    modifier: INCREASED
  - preferred_term: positive regulation of cell population proliferation
    term:
      id: GO:0008284
      label: positive regulation of cell population proliferation
    modifier: INCREASED
  evidence:
  - reference: PMID:24942367
    reference_title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      As PRKD2 and PRKD3 share similar functions with PRKD1 in the diacylglycerol
      and protein kinase C signal transduction pathway, we expanded the
      investigation for these genes by FISH.
    explanation: >-
      Names the shared pathway that makes PRKD1, PRKD2, and PRKD3 lesions
      interchangeable drivers, which is the rationale for this convergence node.
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We identified genetic alterations targeting PRKD genes in the majority
      (78.4%) of tumors in the histologic spectrum of polymorphous adenocarcinoma
      included in this study.
    explanation: >-
      Quantifies PRKD pathway involvement across the histologic spectrum,
      supporting convergence on this node.
  downstream:
  - target: Architecturally Polymorphous Infiltrative Growth
    description: >-
      Constitutive protein kinase D signaling in ductal epithelium drives the
      proliferation and infiltrative growth that produce the tumor's
      characteristic multipattern architecture.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - >-
      The transcriptional and cytoskeletal effectors linking protein kinase D
      activation to the specific multipattern architecture of this tumor have not
      been defined.
- name: Architecturally Polymorphous Infiltrative Growth
  biological_scale: TISSUE
  description: >-
    The transformed cells form a single tumor displaying multiple coexisting
    architectural patterns (tubular, trabecular, cribriform, papillary, solid,
    single-file) while remaining cytologically bland and uniform, and infiltrate
    surrounding tissue with an unencapsulated advancing border. The dissociation
    of architectural variability from cytological uniformity is the defining
    morphological property of the entity and the origin of the name.
  cell_types:
  - preferred_term: salivary gland cell
    term:
      id: CL:0009005
      label: salivary gland cell
  downstream:
  - target: Perineural Invasion
    description: >-
      Infiltrative growth extends into perineural spaces, where the tumor forms
      characteristic concentric cuffs around nerve fascicles.
    causal_link_type: DIRECT
  - target: Regional Lymph Node Metastasis
    description: >-
      Invasive growth permits lymphatic spread to cervical nodes, a step strongly
      conditioned by which PRKD lesion class is present.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - >-
      Lymphatic invasion and nodal colonisation steps have not been characterised
      specifically in this tumor type.
- name: Perineural Invasion
  biological_scale: TISSUE
  description: >-
    Tumor cells stream circumferentially around small nerves in concentric,
    targetoid whorls. Neurotropism is frequent, yet in the largest published
    series it coexisted with excellent long-term outcome after surgical excision
    alone.
  notes: >-
    The often-repeated contrast with adenoid cystic carcinoma — that perineural
    invasion is not an adverse prognostic factor here as it is there — is placed
    in notes rather than asserted as a curated claim, because no source cited in
    this entry tests perineural invasion as a prognostic variable within PAC. What
    the evidence supports is weaker and indirect: neurotropism is frequent, and
    the same series reports about 97.6% of patients alive or dead without disease
    at an average of 115 months, so frequent neurotropism plainly does not carry
    the outcome that ACC's does. The 164-case series does state that PAC must be
    separated from adenoid cystic carcinoma for prognostic reasons, but attributes
    that to the entity, not specifically to perineural invasion.
  evidence:
  - reference: PMID:10421256
    reference_title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The tumors were infiltrative and characterized by a polymorphous growth
      pattern, with individual tumors demonstrating multiple patterns, including
      solid, ductotubular, cribriform, trabecular, and single file growth.
      Neurotropism was identified frequently.
    explanation: >-
      The largest published series reports frequent neurotropism, supporting
      perineural invasion as a characteristic feature.
  - reference: PMID:10421256
    reference_title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At an average of 115.4 months after presentation, approximately 97.6% of all
      patients were either alive or had died without evidence of recurrent disease
      after treatment with surgical excision only.
    explanation: >-
      Establishes excellent long-term outcome in the same cohort in which
      neurotropism was frequent. PARTIAL because the series does not analyse
      perineural invasion as an independent prognostic variable, so this bounds
      rather than proves the claim that it is not adverse here.
- name: Regional Lymph Node Metastasis
  biological_scale: ORGANISM
  description: >-
    Spread to cervical lymph nodes is the principal clinically actionable
    difference within the entity. Fusion-positive tumors metastasized to nodes in
    50% of cases at primary resection whereas hotspot-mutation-positive tumors did
    so in none, and pooled review data show nodal metastasis in about half of
    cribriform tumors against a much lower rate across PAC as a whole. This is why
    subtype and genotype assignment carries surgical consequences for neck
    management.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Among the 37 tested tumors, 9 (24%) were associated with nodal metastasis at
      the time of primary resection, including 8 of 16 (50%) fusion-positive
      tumors, 0 of 14 (0%) mutation-positive tumors
    explanation: >-
      Directly quantifies the genotype-conditioned difference in nodal metastasis
      that this node records.
  - reference: PMID:34023291
    reference_title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      there was an increased incidence of nodal metastasis in CAC (53%) as
      compared with that in PAC of all subtypes
    explanation: >-
      A systematic review independently corroborates the elevated nodal metastasis
      rate of the cribriform subtype.
mechanistic_hypotheses:
- hypothesis_group_id: prkd_convergent_spectrum
  hypothesis_label: Single PRKD-Driven Spectrum Model
  status: CANONICAL
  description: >-
    Conventional PAC, cribriform adenocarcinoma, indeterminate tumors, and
    papillary-predominant tumors form one biological spectrum unified by
    alterations of the PRKD gene family, with the specific lesion (hotspot
    mutation versus rearrangement) explaining the morphological and nodal-risk
    differences rather than marking separate diseases. This is the position taken
    by the WHO classification, which places cribriform adenocarcinoma under the
    PAC heading, and is supported by the shared PRKD genotype across the spectrum
    and by the mutual exclusivity of the two lesion classes.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These findings show that polymorphous adenocarcinoma, cribriform
      adenocarcinoma, tumor with indeterminate features and tumor with predominant
      papillary pattern display marked genetic overlap, and suggest that they may
      represent a spectrum of lesions driven by PRKD gene alterations, rather than
      separate entities.
    explanation: >-
      States the single-spectrum conclusion from shared PRKD genotype across all
      four histologic categories.
- hypothesis_group_id: prkd_pathogenetic_dichotomy
  hypothesis_label: Two-Entity (Pathogenetic Dichotomy) Model
  status: ALTERNATIVE
  description: >-
    Classic PAC and cribriform adenocarcinoma are distinct entities that happen to
    involve the same gene family: the near-restriction of rearrangements to
    cribriform tumors and of the hotspot mutation to classic tumors, combined with
    their different primary sites and sharply different nodal metastasis rates,
    is read as a pathogenetic dichotomy rather than intra-entity variation. The
    original rearrangement study raised exactly this reading, and the naming
    change that folded cribriform adenocarcinoma into PAC was contested on the
    grounds of these clinical behaviour differences. The disagreement is
    unresolved and is not merely nomenclatural, because nodal risk drives whether
    neck dissection is considered.
  evidence:
  - reference: PMID:24942367
    reference_title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Controversy exists as to whether these tumors represent separate entities or
      variants of one spectrum, as they appear to have significant overlap, but
      also clinicopathologic differences.
    explanation: >-
      Frames the two-entity question as genuinely open, supporting ALTERNATIVE
      status for this model.
  - reference: PMID:29761209
    reference_title: "Polymorphous adenocarcinoma of the salivary glands: reappraisal and update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      This approach raised controversy, predominantly because of possible
      differences in clinical behaviour.
    explanation: >-
      Documents that the WHO decision to group cribriform adenocarcinoma under PAC
      was contested specifically on clinical behaviour grounds.
histopathology:
- name: Cytological Uniformity with Architectural Diversity
  diagnostic: true
  description: >-
    The defining feature: multiple architectural patterns coexist within one
    tumor while the individual cells remain bland, small to medium sized, and
    monomorphic. Diagnosis rests on recognising this dissociation, since no single
    pattern is specific.
  evidence:
  - reference: PMID:35507302
    reference_title: "Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Because of its architectural diversity, histological diagnosis of PAC can be
      difficult especially for small biopsies, and immunohistochemistry is of
      great help in differentiating it from its histologic mimics.
    explanation: >-
      Confirms that architectural diversity is the defining and diagnostically
      problematic feature, and the reason immunohistochemistry is needed on small
      biopsies.
- name: Cribriform Pattern
  finding_term:
    preferred_term: Cribriform Pattern
    term:
      id: NCIT:C35920
      label: Cribriform Pattern
  description: >-
    Sieve-like arrangement of tumor cells. Prominent and multinodular in the
    cribriform subtype, from which it takes its name, but also present focally in
    conventional tumors; notably, the measured proportion of cribriform area does
    not by itself predict the underlying PRKD lesion.
- name: Tubular Pattern
  finding_term:
    preferred_term: Tubular Pattern
    term:
      id: NCIT:C35925
      label: Tubular Pattern
  description: >-
    Small ducts and tubules lined by uniform cells, a common component of
    conventional PAC.
- name: Trabecular Pattern
  finding_term:
    preferred_term: Trabecular Pattern
    term:
      id: NCIT:C35913
      label: Trabecular Pattern
  description: >-
    Cords and trabeculae of tumor cells, frequently including single-file
    streaming, which is more characteristic of hotspot-mutant tumors than of
    fusion-positive ones.
- name: Papillary Growth Pattern
  finding_term:
    preferred_term: Papillary Growth Pattern
    term:
      id: NCIT:C35911
      label: Papillary Growth Pattern
  description: >-
    Papillary and papillary-cystic architecture. Papillary growth is
    significantly more common in fusion-positive tumors and has been associated
    with worse outcome, which is the basis for recommending that the percentage of
    papillae be reported.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Such evidence suggests that the percentage of papillae may be predictive of
      the underlying genetic alteration in PRKD genes as well as the clinical
      outcome.
    explanation: >-
      Links papillary proportion to both PRKD genotype and outcome, supporting the
      reporting recommendation.
- name: Solid Growth Pattern
  finding_term:
    preferred_term: Solid Growth Pattern
    term:
      id: NCIT:C36182
      label: Solid Growth Pattern
  description: >-
    Sheets of uniform cells without duct formation, one of the coexisting patterns
    of conventional PAC.
- name: Multinodular Pattern
  finding_term:
    preferred_term: Multinodular Pattern
    term:
      id: NCIT:C35900
      label: Multinodular Pattern
  description: >-
    Multiple discrete tumor nodules, a feature of the cribriform subtype.
- name: Perineural Invasion
  finding_term:
    preferred_term: Perineural Invasion
    term:
      id: NCIT:C48260
      label: Perineural Invasion
  frequency: FREQUENT
  diagnostic: true
  description: >-
    Concentric, targetoid cuffing of small nerves by tumor. Frequent enough to be
    a useful diagnostic clue, though it is shared with adenoid cystic carcinoma
    and so does not discriminate between them on its own.
  notes: >-
    See the Perineural Invasion pathophysiology node for why this entry does not
    curate the common claim that perineural invasion is prognostically benign in
    PAC: no cited source analyses it as an independent prognostic variable within
    this entity.
  evidence:
  - reference: PMID:10421256
    reference_title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The tumors were infiltrative and characterized by a polymorphous growth
      pattern, with individual tumors demonstrating multiple patterns, including
      solid, ductotubular, cribriform, trabecular, and single file growth.
      Neurotropism was identified frequently.
    explanation: >-
      Supports the FREQUENT frequency band for perineural invasion in a 164-case
      series.
- name: Absence of a Distinct Myoepithelial Component
  diagnostic: true
  description: >-
    PAC lacks the true dual luminal/myoepithelial population of adenoid cystic
    carcinoma and pleomorphic adenoma. This underpins the p63-positive but
    p40-negative immunophenotype, because p40 recognises a p63 isoform specific
    for true myoepithelial differentiation.
  evidence:
  - reference: PMID:24969705
    reference_title: "Polymorphous low grade adenocarcinoma has a consistent p63+/p40- immunophenotype that helps distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PLGAs do not harbor a myoepithelial component
    explanation: >-
      States the absence of a myoepithelial component, which is the mechanistic
      basis for the discriminating p63+/p40- pattern.
phenotypes:
- name: Palatal Mass
  category: Clinical
  description: >-
    The characteristic presentation is a slowly enlarging, usually painless
    submucosal swelling of the palate, the single most common site of origin for
    conventional PAC.
  phenotype_term:
    preferred_term: Palatal mass
    term:
      id: HP:0031366
      label: Palate neoplasm
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
  evidence:
  - reference: PMID:42438055
    reference_title: "Polymorphous Adenocarcinoma and Cribriform Adenocarcinoma of Salivary Glands (Cribriform Subtype of PAC): PRKD Mutation, Diagnosis, and Prognosis-A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clinicopathological findings show that the tumor is most common in women and
      on the palate.
    explanation: >-
      A systematic review identifies the palate as the most common site,
      supporting a FREQUENT frequency band for palatal presentation.
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      mutation-positive tumors most frequently originated from the palate (10/14,
      71%) and rarely occurred in base of tongue (1/14, 7%)
    explanation: >-
      Quantifies palatal origin in 71% of hotspot-mutant tumors, supporting the
      FREQUENT band for the conventional subtype.
  - reference: PMID:10421256
    reference_title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The patients usually presented clinically with a palatal mass
    explanation: >-
      A 164-case series reports palatal mass as the usual presentation,
      independently supporting the FREQUENT band.
- name: Salivary Gland Neoplasm
  category: Clinical
  description: >-
    PAC is a neoplasm of salivary gland tissue, overwhelmingly of the minor
    salivary glands; major salivary gland (parotid) primaries occur but are
    uncommon and in reported cases have been fusion-positive.
  phenotype_term:
    preferred_term: Salivary gland neoplasm
    term:
      id: HP:0100684
      label: Salivary gland neoplasm
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The majority (95%; 35/37) of tumors originated in minor salivary glands,
      with the palate being the most frequent site of origin for all tumor types
    explanation: >-
      Confirms salivary gland origin with minor gland predominance.
- name: Neoplasm of the Oral Cavity
  category: Clinical
  description: >-
    Because the minor salivary glands are distributed through the oral mucosa, PAC
    presents as an intraoral malignancy, and is the second most common intraoral
    malignant salivary gland carcinoma after adenoid cystic carcinoma.
  phenotype_term:
    preferred_term: Neoplasm of the oral cavity
    term:
      id: HP:0100649
      label: Neoplasm of the oral cavity
  evidence:
  - reference: PMID:29266837
    reference_title: "The PRKD1 E710D hotspot mutation is highly specific in separating polymorphous adenocarcinoma of the palate from adenoid cystic carcinoma and pleomorphic adenoma on FNA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      is the second most common intraoral malignant salivary gland carcinoma after
      adenoid cystic carcinoma (ACC) and carries an excellent prognosis.
    explanation: >-
      Establishes the intraoral location and the ranking among intraoral salivary
      malignancies.
- name: Neoplasm of the Tongue
  category: Clinical
  description: >-
    The cribriform subtype arises preferentially at the base of tongue rather than
    the palate, a site difference that is one of the strongest arguments for
    treating it as distinct from conventional PAC.
  phenotype_term:
    preferred_term: Base of tongue neoplasm
    term:
      id: HP:0100648
      label: Neoplasm of the tongue
  subtype: Cribriform
  evidence:
  - reference: PMID:34023291
    reference_title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      CAC occurs most frequently in the tongue and PAC in the palate.
    explanation: >-
      Directly supports the tongue predilection of the cribriform subtype.
- name: Cervical Lymphadenopathy from Nodal Metastasis
  category: Clinical
  description: >-
    Regional neck node metastasis, uncommon in conventional PAC but present in
    roughly half of cribriform/fusion-positive tumors at primary resection.
  phenotype_term:
    preferred_term: Cervical lymph node metastasis
    term:
      id: HP:0025289
      label: Cervical lymphadenopathy
  subtype: Cribriform
  evidence:
  - reference: PMID:29761209
    reference_title: "Polymorphous adenocarcinoma of the salivary glands: reappraisal and update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PLGA (PAC, classical variant) only rarely metastasizes, whereas CAMSG often
      shows metastases to the neck lymph nodes.
    explanation: >-
      Contrasts the rare metastasis of classical PAC with frequent neck nodal
      metastasis in the cribriform subtype, supporting the subtype restriction on
      this phenotype.
biochemical:
- name: PRKD1 E710D Hotspot Mutation Testing
  biomarker_term:
    preferred_term: PRKD1 p.E710D hotspot variant
    term:
      id: NCIT:C202963
      label: PRKD1 NP_002733.2:p.E710D
  notes: >-
    Sanger sequencing of the PRKD1 hotspot is the most specific molecular test for
    PAC and works on fine-needle aspiration material, but its sensitivity is only
    moderate, so a negative result does not exclude the diagnosis. Interpretation
    must be hotspot-specific: PRKD1 mutations outside the hotspot argue against
    PAC and towards adenoid cystic carcinoma.
  evidence:
  - reference: PMID:29266837
    reference_title: "The PRKD1 E710D hotspot mutation is highly specific in separating polymorphous adenocarcinoma of the palate from adenoid cystic carcinoma and pleomorphic adenoma on FNA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The specificity of the PRKD1 hotspot mutation for identifying PAC among ACC
      and PA cases was 100% whereas the sensitivity was 50%.
    explanation: >-
      Quantifies both the perfect specificity and the limited sensitivity that
      govern how this test is used.
  - reference: PMID:29266837
    reference_title: "The PRKD1 E710D hotspot mutation is highly specific in separating polymorphous adenocarcinoma of the palate from adenoid cystic carcinoma and pleomorphic adenoma on FNA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Alternative PRKD1 mutations exclude PAC, and are more suggestive of ACC.
    explanation: >-
      Supports the requirement that interpretation be restricted to the hotspot
      rather than any PRKD1 variant.
- name: PRKD1/2/3 Rearrangement Testing
  biomarker_term:
    preferred_term: PRKD1 gene rearrangement
    term:
      id: NCIT:C201783
      label: PRKD1 Gene Rearrangement
  notes: >-
    Break-apart FISH for PRKD1, PRKD2, and PRKD3 detects the fusion class, but
    leaves partners unknown and misses some fusions, so next-generation sequencing
    is preferable in difficult cases given the unusually wide partner repertoire.
    Because fusion status tracks nodal risk, preoperative testing has been
    proposed to inform neck management.
  evidence:
  - reference: PMID:37595638
    reference_title: "Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The wide variety of involved genes is unlike in other salivary gland
      malignancies and warrants a broader strategy of sequencing for molecular
      confirmation for particularly challenging cases, as our NGS study shows.
    explanation: >-
      Supports preferring broad sequencing over break-apart FISH because of the
      unusually diverse partner repertoire.
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      molecular testing for PRKD1/2/3 fusion may be of clinical relevance
      pre-operatively to risk-stratify patients
    explanation: >-
      Supports the proposed preoperative use of fusion testing for nodal risk
      stratification.
- name: p63-Positive, p40-Negative Immunophenotype
  biomarker_term:
    preferred_term: TP63 Gene Product
    term:
      id: NCIT:C128297
      label: TP63 Gene Product
  notes: >-
    The discordant p63-positive/p40-negative pattern is the most useful routine
    immunohistochemical discriminator from adenoid cystic carcinoma and cellular
    pleomorphic adenoma, which show concordant p63/p40 staining. p63 alone is not
    discriminating because all three tumors are frequently p63-positive.
  evidence:
  - reference: PMID:24969705
    reference_title: "Polymorphous low grade adenocarcinoma has a consistent p63+/p40- immunophenotype that helps distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      All 11 PLGAs (100 %) were positive for p63 but completely negative for p40.
    explanation: >-
      Documents the consistent discordant staining pattern in all PAC cases
      tested.
  - reference: PMID:24969705
    reference_title: "Polymorphous low grade adenocarcinoma has a consistent p63+/p40- immunophenotype that helps distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PLGA consistently exhibits a p63+/p40- immunophenotype that can help
      distinguish it from adenoid cystic carcinoma and cellular pleomorphic
      adenoma
    explanation: >-
      States the diagnostic utility of the pattern against the two principal
      mimics.
  - reference: PMID:35507302
    reference_title: "Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Overall, > 90% positivity was observed for pan-cytokeratin (CK) (97.3%),
      CK7 (96.8%), CK7/8 (97.4%), E-cadherin (90.0%), Vimentin (92.5%), S100
      (97.0%), p63 (91.7%), and SOX10 (100%), while little to no positivity was
      observed for CK20 (0.0%), p40 (0.0%), and GFAP (5.0%).
    explanation: >-
      A meta-analysis of 409 cases quantifies the discordant pattern at scale,
      with p63 positive in 91.7% and p40 positive in 0.0%, far exceeding the
      11-case series above.
- name: S100, CK7, and SOX10 Expression
  biomarker_term:
    preferred_term: S100 Calcium Binding Protein
    term:
      id: NCIT:C29924
      label: S100 Calcium Binding Protein
  notes: >-
    The supportive positive profile is CK7-positive, CK20-negative,
    S100-positive, vimentin-positive, SOX10-positive, and GFAP-negative. SOX10
    was positive in every case assessed and S100 in 97.0%, but none of these is
    specific on its own, so they support the diagnosis in combination rather than
    individually. GFAP negativity helps exclude pleomorphic adenoma.
  evidence:
  - reference: PMID:35507302
    reference_title: "Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The results of this systematic review indicate that CK7+/CK20-, p63+/p40-,
      S100+, Vimentin+, and GFAP- immunophenotype have diagnostic value for PAC.
    explanation: >-
      States the composite immunophenotype of diagnostic value, pooled across 32
      studies and 409 cases.
  - reference: PMID:42438055
    reference_title: "Polymorphous Adenocarcinoma and Cribriform Adenocarcinoma of Salivary Glands (Cribriform Subtype of PAC): PRKD Mutation, Diagnosis, and Prognosis-A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      CK7 and S100 IHC markers consistently test positive.
    explanation: >-
      An independent systematic review corroborates consistent CK7 and S100
      positivity.
- name: Low Ki-67 (MIB-1) Proliferation Index
  biomarker_term:
    preferred_term: Ki-67 Labeling Index
    term:
      id: NCIT:C157250
      label: Ki-67 Labeling Index
  notes: >-
    Proliferative activity is low, with a pooled average MIB-1 labeling index
    under 4%. This is the quantitative correlate of the tumor's indolent
    behaviour and supports the diagnosis against higher-grade mimics, though it
    does not by itself separate PAC from other low-grade salivary carcinomas.
  evidence:
  - reference: PMID:35507302
    reference_title: "Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The average MIB-1 labeling index was 3.78%.
    explanation: >-
      Quantifies the low proliferation index pooled across the meta-analysis
      cohort.
diagnosis:
- name: Incisional biopsy
  description: >-
    Diagnosis is established primarily on incisional biopsy of the lesion, ahead
    of definitive resection.
  diagnosis_term:
    preferred_term: incisional biopsy
    term:
      id: NCIT:C15386
      label: Incisional Biopsy
  evidence:
  - reference: PMID:29761209
    reference_title: "Polymorphous adenocarcinoma of the salivary glands: reappraisal and update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The diagnosis is mainly based on an incisional biopsy.
    explanation: >-
      Identifies incisional biopsy as the principal diagnostic procedure.
- name: Immunohistochemical panel
  description: >-
    Immunohistochemistry is the main adjunct to morphology, and is most valuable
    on small biopsies where architectural diversity cannot be appreciated. The
    discriminating result is the discordant p63-positive/p40-negative pattern; the
    supporting profile is CK7-positive, CK20-negative, S100-positive,
    vimentin-positive, SOX10-positive, GFAP-negative, with a low Ki-67 index.
  diagnosis_term:
    preferred_term: immunohistochemistry
    term:
      id: NCIT:C23020
      label: Immunohistochemistry Staining Method
  evidence:
  - reference: PMID:35507302
    reference_title: "Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Because of its architectural diversity, histological diagnosis of PAC can be
      difficult especially for small biopsies, and immunohistochemistry is of
      great help in differentiating it from its histologic mimics.
    explanation: >-
      Establishes immunohistochemistry as the adjunct that resolves the
      small-biopsy problem created by architectural diversity.
- name: PRKD1 hotspot sequencing
  description: >-
    Targeted sequencing of the PRKD1 exon 15 hotspot can be run on fine-needle
    aspiration material as well as resection specimens. It is perfectly specific
    but only moderately sensitive, so it confirms rather than excludes, and only
    the hotspot substitution counts.
  diagnosis_term:
    preferred_term: dideoxy chain termination DNA sequencing
    term:
      id: NCIT:C19641
      label: Dideoxy Chain Termination DNA Sequencing
  evidence:
  - reference: PMID:29266837
    reference_title: "The PRKD1 E710D hotspot mutation is highly specific in separating polymorphous adenocarcinoma of the palate from adenoid cystic carcinoma and pleomorphic adenoma on FNA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The specificity of the PRKD1 hotspot mutation for identifying PAC among ACC
      and PA cases was 100% whereas the sensitivity was 50%.
    explanation: >-
      Quantifies the confirm-but-do-not-exclude character of hotspot sequencing as
      a diagnostic test.
- name: PRKD1/2/3 rearrangement testing
  description: >-
    Break-apart FISH detects the fusion class but leaves partners unidentified and
    misses some fusions; RNA-based next-generation sequencing is preferable in
    difficult cases because the partner repertoire is unusually wide. Relevant
    beyond diagnosis because fusion status tracks nodal risk.
  diagnosis_term:
    preferred_term: next generation sequencing
    term:
      id: NCIT:C101293
      label: Next Generation Sequencing
  evidence:
  - reference: PMID:37595638
    reference_title: "Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The wide variety of involved genes is unlike in other salivary gland
      malignancies and warrants a broader strategy of sequencing for molecular
      confirmation for particularly challenging cases, as our NGS study shows.
    explanation: >-
      Supports preferring broad sequencing over break-apart FISH for molecular
      confirmation in challenging cases.
genetic:
- name: PRKD1
  gene_term:
    preferred_term: PRKD1
    term:
      id: hgnc:9407
      label: PRKD1
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  notes: >-
    Somatic PRKD1 alterations are the principal driver. The p.Glu710Asp kinase
    domain hotspot mutation dominates conventional PAC; PRKD1 rearrangement is an
    alternative, mutually exclusive lesion enriched in the cribriform subtype.
    These are somatic events in a sporadic tumor, not germline predisposition.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      In agreement with previous reports, PRKD1 E710D hotspot mutations were
      mutually exclusive with rearrangements in PRKD1/2/3
    explanation: >-
      Supports the two PRKD1 lesion classes being alternative rather than
      cooperating events in the same tumor.
  case_fractions:
  - population: Polymorphous low-grade adenocarcinoma (original discovery cohort)
    case_fraction_percent: 72.9
    notes: >-
      PRKD1 p.Glu710Asp hotspot mutation frequency in the study that identified
      the lesion.
    evidence:
    - reference: PMID:25240283
      reference_title: "Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        We identified PRKD1 hotspot mutations encoding p.Glu710Asp in 72.9% of
        PLGAs but not in other salivary gland tumors.
      explanation: >-
        Directly reports the 72.9% hotspot mutation share in PLGA.
  - population: Conventional polymorphous adenocarcinoma, centrally reviewed cohort
    case_fraction_percent: 56.0
    cohort_size: 9
    notes: >-
      PRKD1 E710D frequency in histologically classic polymorphous adenocarcinoma
      (5/9), against 20% (2/10) in cribriform adenocarcinoma in the same cohort.
    evidence:
    - reference: PMID:31492931
      reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        polymorphous adenocarcinoma, cribriform adenocarcinoma, and tumor with
        indeterminate features harbored PRKD1 E710D hotspot mutations in 56%
        (5/9), 20% (2/10) and 43% (6/14) of cases, respectively
      explanation: >-
        Reports the per-subtype hotspot mutation shares including the 56% figure
        for conventional PAC.
- name: PRKD2
  gene_term:
    preferred_term: PRKD2
    term:
      id: hgnc:17293
      label: PRKD2
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  notes: >-
    PRKD2 rearrangement is an alternative driver lesion within the same pathway,
    detected in cribriform and indeterminate tumors and rarely in classic PAC.
    Somatic mutations in the PRKD2 kinase domain, by contrast, were not found in
    PRKD1-wild-type classic tumors, so PRKD2 contributes through rearrangement
    rather than point mutation.
  evidence:
  - reference: PMID:24942367
    reference_title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Six additional cases each showed PRKD2 and PRKD3 rearrangements.
    explanation: >-
      Documents PRKD2 rearrangement as a recurrent lesion in this tumor family.
  - reference: PMID:26426580
    reference_title: "Lack of PRKD2 and PRKD3 kinase domain somatic mutations in PRKD1 wild-type classic polymorphous low-grade adenocarcinomas of the salivary gland."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements are
      unlikely to harbour somatic mutations in the kinase domains of PRKD2 or
      PRKD3.
    explanation: >-
      Establishes that PRKD2 involvement is via rearrangement, not kinase domain
      point mutation.
- name: PRKD3
  gene_term:
    preferred_term: PRKD3
    term:
      id: hgnc:9408
      label: PRKD3
  relationship_type: SOMATIC_DRIVER
  variant_origin: SOMATIC
  notes: >-
    PRKD3 rearrangement is the third interchangeable driver lesion, functionally
    equivalent because PRKD3 shares pathway membership with PRKD1 and PRKD2. As
    with PRKD2, kinase domain point mutations were not found in PRKD1-wild-type
    classic tumors.
  evidence:
  - reference: PMID:24942367
    reference_title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      As PRKD2 and PRKD3 share similar functions with PRKD1 in the diacylglycerol
      and protein kinase C signal transduction pathway, we expanded the
      investigation for these genes by FISH.
    explanation: >-
      Gives the pathway rationale for PRKD3 being an interchangeable driver.
- name: ARID1A
  gene_term:
    preferred_term: ARID1A
    term:
      id: hgnc:11110
      label: ARID1A
  relationship_type: COOPERATING
  variant_origin: SOMATIC
  notes: >-
    ARID1A is the prototypical and, with ARID1B, the most common fusion partner
    for the PRKD genes. It contributes the regulatory context of the fusion rather
    than acting as an independent driver here.
  evidence:
  - reference: PMID:37595638
    reference_title: "Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common partners for the PRKD genes were ARID1A and ARID1B.
    explanation: >-
      Identifies ARID1A among the two most common PRKD fusion partners.
- name: DDX3X
  gene_term:
    preferred_term: DDX3X
    term:
      id: hgnc:2745
      label: DDX3X
  relationship_type: COOPERATING
  variant_origin: SOMATIC
  notes: >-
    DDX3X was one of the two originally described PRKD1 fusion partners in
    cribriform adenocarcinoma.
  evidence:
  - reference: PMID:24942367
    reference_title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The RNAseq of 2 CAMSGs showed ARID1A-PRKD1 and DDX3X-PRKD1 fusions,
      respectively, while no fusion candidates were identified in two PLGAs.
    explanation: >-
      Documents DDX3X-PRKD1 as one of the two founding fusions of this entity.
treatments:
- name: Wide Surgical Excision
  description: >-
    Complete surgical excision with clear margins is the mainstay of treatment and
    is usually definitive: in the largest series, treatment with excision alone
    left about 97.6% of patients alive or dead without disease at an average of
    115 months. Sources differ on how wide is wide enough — one review specifies
    wide excision, while the 164-case series recommends conservative but complete
    excision — so the shared commitment is completeness of removal rather than a
    particular margin width.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: surgical procedure
    term:
      id: NCIT:C15329
      label: Surgical Procedure
  target_mechanisms:
  - target: Architecturally Polymorphous Infiltrative Growth
    treatment_effect: INHIBITS
    description: >-
      Resection with clear margins removes the infiltrative tumor mass; the
      unencapsulated advancing border is the reason wide rather than enucleating
      excision is required.
  evidence:
  - reference: PMID:29761209
    reference_title: "Polymorphous adenocarcinoma of the salivary glands: reappraisal and update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The optimal treatment comprises wide surgical excision, often with adjuvant
      radiotherapy. In general, PAC has a good prognosis.
    explanation: >-
      Establishes wide surgical excision as the optimal primary treatment and the
      generally good prognosis.
  - reference: PMID:10421256
    reference_title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Conservative but complete surgical excision is the treatment of choice for
      these slow-growing tumors with a low proliferation index; adjuvant therapy
      does not appear to alter the prognosis.
    explanation: >-
      The largest series names complete surgical excision as the treatment of
      choice, and is the source of the conservative-versus-wide tension noted in
      the description.
  - reference: PMID:10421256
    reference_title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At an average of 115.4 months after presentation, approximately 97.6% of all
      patients were either alive or had died without evidence of recurrent disease
      after treatment with surgical excision only.
    explanation: >-
      Quantifies the durability of excision alone, supporting surgery as usually
      definitive.
- name: Adjuvant Radiotherapy
  description: >-
    Radiotherapy is used adjunctively, conventionally for adverse features such as
    positive or close margins or recurrent disease. Its benefit is not
    established: one systematic review reports resection with adjuvant
    radiotherapy as conventional and effective with no documented tumor-related
    deaths, but the 164-case series states directly that adjuvant therapy does not
    appear to alter the prognosis, and reports about 97.6% freedom from disease
    after excision alone. Against so high a surgical cure rate there is little
    room for an adjuvant effect to show, so this entry records radiotherapy as
    conventionally used rather than as demonstrated to improve outcome.
  therapeutic_modality: RADIOTHERAPY
  treatment_term:
    preferred_term: radiation therapy
    term:
      id: NCIT:C15313
      label: Radiation Therapy
  evidence:
  - reference: PMID:42438055
    reference_title: "Polymorphous Adenocarcinoma and Cribriform Adenocarcinoma of Salivary Glands (Cribriform Subtype of PAC): PRKD Mutation, Diagnosis, and Prognosis-A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Resection and adjuvant radiotherapy are the conventional and effective
      treatments, with no documented tumor-related deaths.
    explanation: >-
      Supports resection plus adjuvant radiotherapy as the conventional effective
      approach and documents the absence of tumor-related deaths.
  - reference: PMID:10421256
    reference_title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Conservative but complete surgical excision is the treatment of choice for
      these slow-growing tumors with a low proliferation index; adjuvant therapy
      does not appear to alter the prognosis.
    explanation: >-
      The largest series finds no prognostic benefit from adjuvant therapy,
      directly opposing the claim that adjuvant radiotherapy improves outcome;
      recorded as REFUTE so the disagreement is machine-visible rather than
      averaged away in prose.
- name: Neck Dissection for Fusion-Positive or Cribriform Disease
  description: >-
    Regional lymph node dissection is considered when nodal risk is high, that is
    for cribriform-subtype or fusion-positive tumors, in which nodal metastasis is
    present in roughly half of cases at primary resection. This is the one place
    where subtype and genotype assignment changes surgical management, and it is
    the practical reason the one-entity versus two-entity question matters.
    Conventional hotspot-mutant palatal tumors do not warrant elective neck
    treatment on current evidence.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: neck dissection
    term:
      id: NCIT:C15643
      label: Neck Dissection
  target_mechanisms:
  - target: Regional Lymph Node Metastasis
    treatment_effect: INHIBITS
    description: >-
      Neck dissection addresses established or high-risk regional nodal disease in
      the fusion-positive/cribriform group.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Fusion-positive tumors, however, appear to be more aggressive clinically and
      may require additional treatments (e.g. neck dissection).
    explanation: >-
      Directly supports considering neck dissection specifically for
      fusion-positive tumors.
  - reference: PMID:34023291
    reference_title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      these tumors likely comprise a significant portion of the cases of PAC with
      poor outcomes and are deserving of attention and consideration for
      escalation in oncologic treatment.
    explanation: >-
      Supports treatment escalation for the cribriform subgroup on the basis of
      its worse regional behaviour.
discussions:
- discussion_id: pac_prkd_wildtype_driver_gap
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    What drives the substantial minority of polymorphous adenocarcinomas that
    carry neither the PRKD1 hotspot mutation nor a PRKD1/2/3 rearrangement?
  attaches_to:
  - pathophysiology#Deregulated Protein Kinase D Signaling
  rationale: >-
    Roughly one fifth of tumors across the PAC spectrum have no detectable PRKD
    alteration, and the obvious candidate explanation has been actively excluded:
    kinase domain sequencing of PRKD2 and PRKD3 in PRKD1-wild-type classic tumors
    found no mutations. Whether these cases are driven by non-hotspot PRKD1
    lesions, by cryptic rearrangements missed by break-apart FISH, by epigenetic
    activation of the same pathway, or by a genuinely different mechanism is
    unresolved. This matters for the convergence claim in this entry: if the
    wild-type cases are driven by something other than protein kinase D, then PAC
    is not a single-pathway disease.
  proposed_experiments:
  - experiment_id: exp_pac_wgs_rnaseq_prkd_wildtype
    name: Whole-genome and RNA sequencing of PRKD-wild-type PAC
    description: >-
      Apply whole-genome and RNA sequencing to tumors lacking both the PRKD1
      hotspot mutation and PRKD1/2/3 rearrangements, which prior studies could not
      do for want of frozen material, to detect non-hotspot PRKD1 variants,
      cryptic fusions, and alternative drivers.
  - experiment_id: exp_pac_pathway_activity_readout
    name: Direct protein kinase D pathway activity readout across genotypes
    description: >-
      Measure protein kinase D substrate phosphorylation in hotspot-mutant,
      fusion-positive, and wild-type tumors to test whether wild-type cases
      nonetheless show pathway activation, which would support convergence by a
      non-genetic route.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      We did not identify genetic alterations in PRKD genes in 21.6% (n=7) of the
      cases studied.
    explanation: >-
      Quantifies the PRKD-wild-type fraction that constitutes this gap.
  - reference: PMID:26426580
    reference_title: "Lack of PRKD2 and PRKD3 kinase domain somatic mutations in PRKD1 wild-type classic polymorphous low-grade adenocarcinomas of the salivary gland."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Further studies are warranted to define the driver genetic events
    explanation: >-
      The study that excluded PRKD2/PRKD3 kinase domain mutations explicitly
      leaves the driver of these cases undefined.
- discussion_id: pac_casg_entity_boundary
  kind: CONTROVERSY
  status: OPEN
  prompt: >-
    Should cribriform adenocarcinoma of salivary gland be curated as a subtype of
    polymorphous adenocarcinoma or as a separate disease entity?
  attaches_to:
  - pathophysiology#Regional Lymph Node Metastasis
  rationale: >-
    This entry follows the WHO classification and NCIT in modeling cribriform
    adenocarcinoma as a subtype, and records the competing reading as an
    ALTERNATIVE mechanistic hypothesis rather than silently resolving it. The
    disagreement is empirically grounded on both sides: shared PRKD genotype and a
    continuum of indeterminate cases favour one spectrum, while different primary
    site, different lesion class, and a roughly ten-fold difference in nodal
    metastasis rate favour two entities. It is also not purely academic, because
    nodal risk determines whether neck dissection is considered. Should dismech
    later split these into separate Disease entries, the natural structure would be
    two entries plus a Grouping with SHARED_PATHWAY basis.
  evidence:
  - reference: PMID:29761209
    reference_title: "Polymorphous adenocarcinoma of the salivary glands: reappraisal and update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Previously, PAC was referred to as polymorphous low-grade adenocarcinoma
      (PLGA), but the new WHO classification of salivary gland tumours has also
      included under the PAC subheading, the so-called cribriform adenocarcinoma
      of minor salivary glands (CAMSG).
    explanation: >-
      Documents the WHO decision this entry follows in treating cribriform
      adenocarcinoma as a subtype.
  - reference: PMID:34023291
    reference_title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Recently, histologic grade was removed from salivary tumor nomenclature by
      the WHO to include disease of higher grade.
    explanation: >-
      Explains why "low-grade" was dropped from the name: the entity as now
      defined admits higher-grade disease, which is the same widening that
      brought cribriform adenocarcinoma under the PAC heading.
  - reference: PMID:34023291
    reference_title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      One such entity, cribriform adenocarcinoma (CAC), is an aggressive group of
      polymorphous adenocarcinoma (PAC), with frequent nodal metastasis and
      locoregional recurrence.
    explanation: >-
      Characterises cribriform adenocarcinoma as an aggressive group within PAC;
      counted as PARTIAL because the source adopts the subtype reading rather
      than adjudicating between the one-entity and two-entity models.
- discussion_id: pac_prkd_prognostic_significance
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Do PRKD alterations carry independent prognostic information, or are they only
    diagnostic and subtype-defining markers?
  attaches_to:
  - pathophysiology#Regional Lymph Node Metastasis
  rationale: >-
    Fusion status correlates strongly with nodal metastasis, yet recurrence-free
    survival did not differ between fusion-positive and mutation-positive tumors
    in the cohort where that comparison was made, and the authors attribute this to
    limited power given how rare recurrence is. A recent systematic review
    concludes that the prognostic significance of PRKD alterations remains
    inconclusive while their diagnostic value is established. Because
    tumor-related death is essentially absent, any prognostic endpoint must be
    regional control or recurrence rather than survival, which makes adequately
    powered studies difficult.
  proposed_experiments:
  - experiment_id: exp_pac_multicentre_genotype_outcome
    name: Multicentre genotype-stratified outcome study with regional-control endpoints
    description: >-
      Pool genotyped PAC-spectrum cases across centres with sufficient follow-up
      to test whether PRKD lesion class predicts regional recurrence and
      nodal relapse independently of histologic subtype and papillary proportion.
  evidence:
  - reference: PMID:42438055
    reference_title: "Polymorphous Adenocarcinoma and Cribriform Adenocarcinoma of Salivary Glands (Cribriform Subtype of PAC): PRKD Mutation, Diagnosis, and Prognosis-A Systematic Review."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PRKD alterations serve primarily as diagnostic markers, and their prognostic
      significance remains inconclusive.
    explanation: >-
      A systematic review states directly that the prognostic role is unresolved
      while the diagnostic role is established.
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      our study may have a limited statistical power to assess the prognostic
      significance of PRKD1 E710D hotspot mutations or PRKD1/2/3 rearrangements in
      predicting clinical outcomes
    explanation: >-
      The authors explicitly identify limited power as the reason the prognostic
      question is unresolved.
- discussion_id: pac_no_model_systems_gap
  kind: KNOWLEDGE_GAP
  status: OPEN
  prompt: >-
    Why is there no experimental model of polymorphous adenocarcinoma, and what
    would one have to reproduce to be useful?
  attaches_to:
  - pathophysiology#Deregulated Protein Kinase D Signaling
  - pathophysiology#Architecturally Polymorphous Infiltrative Growth
  rationale: >-
    This entry carries no experimental_models, animal_models, or
    computational_models, and that is a statement about the field rather than an
    omission in curation: no established cell line, organoid, or genetically
    engineered animal model of PAC is in routine use. The consequence is visible
    in the pathograph itself — the step from protein kinase D activation to the
    tumor's characteristic multipattern architecture is
    INDIRECT_UNKNOWN_INTERMEDIATES precisely because there is no system in which
    to interrogate it. Even primary material is scarce: the study that defined the
    PRKD-wild-type subset could not pursue it for want of frozen tissue. A useful
    model would need to reproduce the defining dissociation of architectural
    diversity from cytological uniformity, not merely express the mutant kinase.
  proposed_experiments:
  - experiment_id: exp_pac_e710d_salivary_organoid
    name: PRKD1 E710D knock-in salivary gland organoids
    description: >-
      Introduce the E710D hotspot substitution into human salivary gland
      epithelial organoids and test whether activated protein kinase D alone
      produces multipattern architecture with retained cytological uniformity, or
      whether additional context is required.
  - experiment_id: exp_pac_fusion_vs_hotspot_comparison
    name: Side-by-side fusion versus hotspot models of nodal propensity
    description: >-
      Build matched models carrying a PRKD fusion and the PRKD1 hotspot mutation
      and compare invasive and lymphatic behaviour, to test whether the 50%
      versus 0% nodal metastasis difference is intrinsic to the lesion class
      rather than a correlate of tumor site.
  - experiment_id: exp_pac_conditional_knockin_mouse
    name: Conditional salivary-epithelial Prkd1 E710D knock-in mouse
    description: >-
      Restrict expression of the activating allele to salivary gland epithelium to
      test whether a whole-organism model develops an indolent, neurotropic
      palatal tumor resembling human PAC.
  evidence:
  - reference: PMID:31492931
    reference_title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      regrettably, representative frozen samples from these PRKD1/2/3 wild-type
      tumors were unavailable
    explanation: >-
      Documents that even primary tissue is limiting for mechanistic follow-up in
      this tumor; PARTIAL because it evidences scarcity of material rather than
      the absence of model systems as such, which is an absence no single
      publication asserts.
- discussion_id: pac_mondo_term_gap
  kind: CURATION_TODO
  status: OPEN
  prompt: >-
    MONDO lacks a class for polymorphous adenocarcinoma, so what should anchor
    disease_term?
  rationale: >-
    Searching MONDO labels and exact synonyms returns no polymorphous
    adenocarcinoma class, and no MONDO term cross-references NCIT:C35702 or its
    parent NCIT:C8021 (Salivary Gland Adenocarcinoma). disease_term is therefore
    anchored to the nearest MONDO superclass, salivary gland carcinoma
    (MONDO:0000521), with exact identity carried in ncit_mappings as
    skos:exactMatch. This is a deliberate broadMatch-by-necessity, not an
    assertion of equivalence between PAC and salivary gland carcinoma. A MONDO
    term request for polymorphous adenocarcinoma, with the two NCIT subtypes,
    would let disease_term be tightened.
  evidence:
  - reference: PMID:29266837
    reference_title: "The PRKD1 E710D hotspot mutation is highly specific in separating polymorphous adenocarcinoma of the palate from adenoid cystic carcinoma and pleomorphic adenoma on FNA."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      PAC demonstrates cytological overlap with 2 other salivary gland tumors
      frequently encountered in the same location, namely ACC and pleomorphic
      adenoma (PA).
    explanation: >-
      Establishes that PAC is a distinct entity requiring separation from named
      mimics, which is why a dedicated ontology class is warranted rather than
      reliance on a broad parent.
references:
- reference: PMID:25240283
  title: "Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands."
- reference: PMID:24942367
  title: "Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin."
- reference: PMID:31492931
  title: "Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes."
- reference: PMID:37595638
  title: "Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners."
- reference: PMID:29266837
  title: "The PRKD1 E710D hotspot mutation is highly specific in separating polymorphous adenocarcinoma of the palate from adenoid cystic carcinoma and pleomorphic adenoma on FNA."
- reference: PMID:24969705
  title: "Polymorphous low grade adenocarcinoma has a consistent p63+/p40- immunophenotype that helps distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma."
- reference: PMID:29761209
  title: "Polymorphous adenocarcinoma of the salivary glands: reappraisal and update."
- reference: PMID:34023291
  title: "How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review."
- reference: PMID:42438055
  title: "Polymorphous Adenocarcinoma and Cribriform Adenocarcinoma of Salivary Glands (Cribriform Subtype of PAC): PRKD Mutation, Diagnosis, and Prognosis-A Systematic Review."
- reference: PMID:26426580
  title: "Lack of PRKD2 and PRKD3 kinase domain somatic mutations in PRKD1 wild-type classic polymorphous low-grade adenocarcinomas of the salivary gland."
- reference: PMID:35507302
  title: "Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis."
- reference: PMID:10421256
  title: "Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases."
📚

References & Deep Research

References

12
PMID:25240283
Hotspot activating PRKD1 somatic mutations in polymorphous low-grade adenocarcinomas of the salivary glands.
No top-level findings curated for this source.
PMID:24942367
Novel PRKD gene rearrangements and variant fusions in cribriform adenocarcinoma of salivary gland origin.
No top-level findings curated for this source.
PMID:31492931
Histologic spectrum of polymorphous adenocarcinoma of the salivary gland harbor genetic alterations affecting PRKD genes.
No top-level findings curated for this source.
PMID:37595638
Comprehensive Molecular Characterization of Polymorphous Adenocarcinoma, Cribriform Subtype: Identifying Novel Fusions and Fusion Partners.
No top-level findings curated for this source.
PMID:29266837
The PRKD1 E710D hotspot mutation is highly specific in separating polymorphous adenocarcinoma of the palate from adenoid cystic carcinoma and pleomorphic adenoma on FNA.
No top-level findings curated for this source.
PMID:24969705
Polymorphous low grade adenocarcinoma has a consistent p63+/p40- immunophenotype that helps distinguish it from adenoid cystic carcinoma and cellular pleomorphic adenoma.
No top-level findings curated for this source.
PMID:29761209
Polymorphous adenocarcinoma of the salivary glands: reappraisal and update.
No top-level findings curated for this source.
PMID:34023291
How Increased Nodal Metastasis and Recurrence in Cribriform Adenocarcinoma Relate to Polymorphous Adenocarcinoma and Survival: A Systematic Review.
No top-level findings curated for this source.
PMID:42438055
Polymorphous Adenocarcinoma and Cribriform Adenocarcinoma of Salivary Glands (Cribriform Subtype of PAC): PRKD Mutation, Diagnosis, and Prognosis-A Systematic Review.
No top-level findings curated for this source.
PMID:26426580
Lack of PRKD2 and PRKD3 kinase domain somatic mutations in PRKD1 wild-type classic polymorphous low-grade adenocarcinomas of the salivary gland.
No top-level findings curated for this source.
PMID:35507302
Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis.
No top-level findings curated for this source.
PMID:10421256
Polymorphous low grade adenocarcinoma: a clinicopathologic study of 164 cases.
No top-level findings curated for this source.

Deep Research

1
Falcon ▸
Salivary Gland Polymorphous Adenocarcinoma: Research Report
Edison Scientific Literature 11 citations 2026-08-05T22:58:13.510924

Salivary Gland Polymorphous Adenocarcinoma: Research Report

Executive summary

Polymorphous adenocarcinoma (PAC) is a rare malignant epithelial neoplasm arising predominantly in the minor salivary glands, especially those of the palate. It combines cytologic uniformity with marked architectural diversity and infiltrative growth. Most conventional PACs behave indolently, but local recurrence, nodal metastasis, distant metastasis, and occasional high-grade transformation are possible; accordingly, the World Health Organization removed “low-grade” from the former name polymorphous low-grade adenocarcinoma. The cribriform subtype lies within the current PAC spectrum but is enriched for PRKD-family rearrangements and may have greater nodal metastatic potential than conventional PAC. The strongest established molecular feature is a somatic alteration of the protein kinase D family—particularly PRKD1 p.Glu710Asp (E710D) in conventional PAC and PRKD1/PRKD2/PRKD3 rearrangements in cribriform tumors. Diagnosis remains morphology-first, supported by immunohistochemistry and, in difficult cases, PRKD molecular testing. Complete surgical excision is the principal treatment; evidence for systemic or genotype-directed therapy is currently insufficient. (nonaka2022immunohistochemicalprofileof pages 1-3, iyer2021anoverviewon pages 11-12)

The evidence retrieved for this report is strongest for classification, pathology, immunophenotype, and molecular diagnosis, but weaker for disease-specific incidence, quality of life, prospective treatment outcomes, and experimental models.

Domain Key findings Numeric details Evidence type Source year / DOI Citation
Entity / classification Polymorphous adenocarcinoma (PAC) is a malignant salivary gland tumor, predominantly of minor salivary glands, with morphologic diversity, infiltrative growth, and generally low metastatic potential; originally described as polymorphous low-grade adenocarcinoma and renamed by WHO to PAC to reflect a broader biologic spectrum including higher-grade variants. Systematic review dataset: 409 PAC cases from 32 studies (1988-2021). Systematic review / meta-analysis; narrative review 2022, https://doi.org/10.1007/s12105-022-01453-6; 2021, https://doi.org/10.3390/cancers13153910 (nonaka2022immunohistochemicalprofileof pages 1-3, iyer2021anoverviewon pages 11-12)
Anatomy / clinical course PAC arises mainly in minor salivary glands; diagnosis is often straightforward in the palate but can be difficult in uncommon sites such as the oropharynx, sinonasal tract, and nasopharynx. Clinical course is usually indolent/favorable, though aggressive behavior can occur. Common-site emphasis: palate; uncommon sites specifically listed: oropharynx, sinonasal tract, nasopharynx. Systematic review / meta-analysis; narrative review 2022, https://doi.org/10.1007/s12105-022-01453-6; 2021, https://doi.org/10.3390/cancers13153910 (nonaka2022immunohistochemicalprofileof pages 1-3, nonaka2022immunohistochemicalprofileof pages 4-6, iyer2021anoverviewon pages 11-12)
Pathology / IHC Characteristic features include cytologic uniformity with architectural diversity, infiltrative borders/growth, and possible myxohyaline matrix. Helpful IHC profile: CK7+/CK20−, p63+/p40−, S100+, vimentin+, GFAP−; p63+/p40− is especially useful against adenoid cystic carcinoma. Positive staining rates: pan-cytokeratin 97.3%, CK7 96.8%, CK7/8 97.4%, E-cadherin 90%, vimentin 92.5%, S100 97%, p63 91.7%, SOX10 100%; negative: CK20 0%, p40 0%, GFAP 5%; p63+/p40− in PAC 38/39 (97.4%) vs ACC 1/155 (0.006%); OR 801.32; mean MIB-1 labeling index 3.78%. Systematic review / meta-analysis 2022, https://doi.org/10.1007/s12105-022-01453-6 (nonaka2022immunohistochemicalprofileof pages 8-10, nonaka2022immunohistochemicalprofileof pages 1-3, nonaka2022immunohistochemicalprofileof pages 4-6)
Molecular genetics PAC is associated with PRKD1 alterations on chromosome 14; the PRKD1 E710D hotspot mutation is highlighted as a useful ancillary diagnostic marker. PRKD-family signaling is linked to migration/differentiation through MAPK and RAS-related pathways. Cribriform adenocarcinoma has been incorporated into the PAC spectrum, although debate remains. Specific retrieved numeric frequency not available in current evidence; hotspot named: PRKD1 E710D. Narrative review 2021, https://doi.org/10.3390/cancers13153910 (iyer2021anoverviewon pages 11-12)
Diagnosis Diagnosis remains morphology-based, with IHC and molecular testing as adjuncts. The most clinically important differential diagnosis is adenoid cystic carcinoma; p63+/p40− strongly favors PAC. FISH has shown reasonable success for detecting PRKD1 alterations. Differential performance metric: OR 801.32 for p63+/p40− pattern distinguishing PAC from ACC; PAC 38/39 vs ACC 1/155. Systematic review / meta-analysis; narrative review 2022, https://doi.org/10.1007/s12105-022-01453-6; 2021, https://doi.org/10.3390/cancers13153910 (nonaka2022immunohistochemicalprofileof pages 8-10, nonaka2022immunohistochemicalprofileof pages 1-3, iyer2021anoverviewon pages 11-12)
Treatment Retrieved disease-specific evidence indicates correct diagnosis is clinically important because management differs from mimics; broader salivary gland review states surgical resection is principal treatment for most salivary gland neoplasms, with other modalities used according to behavior/stage. No PAC-specific response-rate or regimen-level numeric outcomes available in retrieved evidence. Systematic review commentary; narrative review 2022, https://doi.org/10.1007/s12105-022-01453-6; 2021, https://doi.org/10.3390/cancers13153910 (nonaka2022immunohistochemicalprofileof pages 8-10, iyer2021anoverviewon pages 11-12)
Prognosis PAC generally has a favorable prognosis, but regional and distant metastases can occur and may become difficult to control; WHO renaming reflects recognition that behavior is not uniformly “low grade.” No survival percentage, recurrence rate, or metastasis rate captured in current retrieved evidence. Systematic review / meta-analysis; narrative review 2022, https://doi.org/10.1007/s12105-022-01453-6; 2021, https://doi.org/10.3390/cancers13153910 (nonaka2022immunohistochemicalprofileof pages 8-10, nonaka2022immunohistochemicalprofileof pages 1-3, iyer2021anoverviewon pages 11-12)
Evidence gaps Current retrieved evidence is strongest for classification, morphology, and IHC; it is comparatively weak for PAC-specific epidemiology, environmental risk factors, treatment algorithms, survival statistics, and modern omics/clinical-trial data. Missing from retrieved evidence: incidence/prevalence, sex ratio, age distribution, survival %, recurrence %, metastatic %, prospective trials, validated biomarkers beyond diagnostic adjuncts. Evidence synthesis gap assessment Based on retrieved 2021-2022 evidence (nonaka2022immunohistochemicalprofileof pages 8-10, nonaka2022immunohistochemicalprofileof pages 1-3, iyer2021anoverviewon pages 11-12, nonaka2022immunohistochemicalprofileof pages 4-6)

Table: This table condenses the most relevant retrieved evidence on salivary gland polymorphous adenocarcinoma, emphasizing classification, diagnostic pathology, PRKD-related molecular findings, and where the current evidence remains limited.

1. Disease information

Definition and classification

PAC is an infiltrating salivary carcinoma characterized by monomorphic tumor cells but polymorphous architecture, including tubular, trabecular, cribriform, targetoid, papillary, and solid configurations. It was recognized as a distinct entity in 1984 under the name polymorphous low-grade adenocarcinoma (PLGA). WHO classification subsequently adopted polymorphous adenocarcinoma, reflecting the fact that not every tumor is biologically low grade. Cribriform adenocarcinoma of salivary gland is currently included in the PAC spectrum, although its precise taxonomic separation remains debated. (nonaka2022immunohistochemicalprofileof pages 1-3, iyer2021anoverviewon pages 11-12, nonaka2022immunohistochemicalprofileof pages 4-6)

Synonyms: polymorphous adenocarcinoma; polymorphous low-grade adenocarcinoma; PLGA; terminal duct carcinoma; lobular carcinoma of salivary gland. “Cribriform adenocarcinoma of salivary gland/minor salivary gland” and “cribriform adenocarcinoma of the tongue” are related historical terms, but should not be treated as exact synonyms without recording the cribriform subtype.

Identifiers and coding:

  • MONDO: a PAC-specific MONDO identifier could not be verified from the retrieved primary literature; use the current MONDO release rather than inferring an identifier.
  • MeSH: generally indexed under Adenocarcinoma and Salivary Gland Neoplasms; a uniquely specific MeSH descriptor was not established in the retrieved evidence.
  • ICD-10-CM: coding is anatomical rather than histology-specific—typically C05.- for palate, C06.- for other/unspecified mouth, C08.0-C08.9 for other salivary glands, or another site-appropriate malignant-neoplasm code.
  • ICD-O: malignant salivary tumor coding requires both a topography code and morphology code; the current registry/WHO edition should be consulted because older records may retain PLGA terminology.
  • OMIM/Orphanet: PAC is a sporadic neoplasm, not an established Mendelian disorder; no disease-specific OMIM entry was verified. An Orphanet-specific identifier was not confirmed in the retrieved literature.
  • Suggested ontology concept: NCIT Polymorphous Adenocarcinoma; MONDO mapping should be curated against the current release rather than generated from the name alone.

The information summarized here is aggregated disease-level evidence from systematic reviews and clinicopathologic literature, not individual EHR data. The 2022 immunohistochemical meta-analysis included 409 PAC cases from 32 studies published during 1988–2021. (nonaka2022immunohistochemicalprofileof pages 1-3)

2. Etiology and risk factors

PAC is best understood as a sporadic, somatically driven neoplasm. PRKD alterations are tumor-acquired molecular drivers/diagnostic markers; they are not presently evidence of inherited susceptibility. No reproducible germline causal variant, Mendelian inheritance pattern, founder mutation, carrier frequency, or PAC-specific polygenic-risk model has been established in the retrieved evidence. (iyer2021anoverviewon pages 11-12)

No PAC-specific causal association has been demonstrated for tobacco, alcohol, diet, occupational toxins, ionizing radiation, pollution, chronic inflammation, or infectious agents. Age and female sex have been overrepresented in historical clinical series, but these are demographic associations rather than proven causal exposures. Likewise, no genetic or environmental protective factors and no validated gene–environment interaction are known. These conclusions denote absence of established evidence, not proof that such effects are impossible.

3. Phenotypes

PAC usually presents in adulthood as a slow-growing, painless, firm submucosal mass, most often on the palate. Ulceration, pain, paresthesia, dysphagia, dysarthria, or fixation can occur with larger, ulcerated, or nerve-involving lesions. The clinical course is commonly chronic and insidious. Regional lymph-node enlargement may be the first indication of a cribriform-subtype tumor. PAC can exhibit perineural invasion microscopically even without prominent neurologic symptoms. Architectural patterns include cribriform, tubular, and solid growth with infiltrative borders. (nonaka2022immunohistochemicalprofileof pages 8-10, nonaka2022immunohistochemicalprofileof pages 4-6)

Suggested phenotype annotations include:

  • Oral mass — HP:0031000, Oral cavity neoplasm or the most specific current HPO neoplasm term.
  • Palatal mass — map through oral-cavity neoplasm plus palate anatomy.
  • Slow tumor growth — HP:0003002, Breast carcinoma is not appropriate; a general neoplasm/progression annotation should instead be represented in a disease-course ontology because HPO lacks a consistently granular “slow-growing tumor” term.
  • Pain — HP:0012531, Pain.
  • Dysphagia — HP:0002015.
  • Dysarthria — HP:0001260.
  • Paresthesia — HP:0003401.
  • Enlarged cervical lymph nodes — HP:0025280, Cervical lymphadenopathy.
  • Perineural invasion, recurrence, and metastasis are better represented using NCIT/SNOMED cancer-pathology concepts than patient-phenotype HPO terms.

Reliable phenotype frequencies, validated patient-reported outcome scores, and PAC-specific EQ-5D, SF-36, or PROMIS data were not identified. Quality-of-life effects therefore must be inferred from site and treatment: oral pain, impaired speech/swallowing, palatal defects, xerostomia after irradiation, and anxiety associated with prolonged recurrence surveillance.

4. Genetic and molecular information

Core somatic alterations

The principal molecular association is PRKD-family activation. Conventional PAC is associated particularly with PRKD1 E710D, a hotspot missense substitution in the kinase domain. PRKD1 is located on chromosome 14 and encodes a serine/threonine protein kinase involved in cellular migration and differentiation and linked to RAS/MAPK-associated signaling. The mutation is an acquired tumor alteration and is used as an ancillary diagnostic marker rather than as a germline predictive test. (iyer2021anoverviewon pages 11-12)

Cribriform-subtype PAC is more often associated with rearrangements involving PRKD1, PRKD2, or PRKD3, with diverse fusion partners reported in the literature. Recent developments include increasingly broad RNA-sequencing identification of novel PRKD1 partners, reinforcing the concept that the conserved event is kinase-family dysregulation rather than one universal fusion partner. These rearrangements are structural somatic alterations; their population allele frequency is therefore not meaningfully assessed in gnomAD as an inherited allele.

Variant interpretation: PRKD1 E710D and recurrent PRKD-family fusions are oncogenic/pathogenic at the somatic tumor level. Germline ACMG/AMP categories should not automatically be applied to them. No validated inherited penetrance, anticipation, mosaic carrier risk, or reproductive recurrence risk is known.

Immunophenotype and proliferation

A 2022 systematic review/meta-analysis found PAC positivity for pan-cytokeratin 97.3%, CK7 96.8%, CK7/8 97.4%, E-cadherin 90%, vimentin 92.5%, S100 97%, p63 91.7%, and SOX10 100%. CK20 and p40 were reported as 0% positive, GFAP as 5%, and mean MIB-1/Ki-67 labeling index as 3.78%. The practical profile is CK7+/CK20−, S100+, vimentin+, p63+/p40−, GFAP−. These data are aggregated and marker estimates may be affected by small denominators and inter-study assay variation. (nonaka2022immunohistochemicalprofileof pages 1-3)

No validated PAC-specific modifier genes, methylation signature in routine practice, proteomic/metabolomic/lipidomic signature, circulating biomarker, or inherited pharmacogenomic marker was identified. Recent methylation-classification work in salivary tumors is promising but is not yet a standard PAC diagnostic test.

5. Environmental information

No environmental, lifestyle, or infectious trigger is established specifically for PAC. Tobacco and alcohol are major exposures for mucosal squamous carcinoma but should not be imported as proven PAC risk factors. No bacterial, viral, fungal, or parasitic etiology is recognized. Consequently, there is no PAC-specific CHEBI toxicant annotation supported by current evidence.

6. Mechanism and pathophysiology

A plausible disease chain is:

  1. A minor-salivary-gland epithelial progenitor acquires a somatic PRKD1 hotspot mutation or PRKD-family rearrangement.
  2. Altered protein kinase D signaling affects kinase activity and downstream programs governing epithelial differentiation, adhesion, migration, and RAS/MAPK-linked signaling.
  3. A cytologically uniform clone develops multiple architectural growth patterns.
  4. Infiltrative and targetoid growth around nerves produces local tissue invasion and microscopic perineural invasion.
  5. Additional, incompletely defined events may produce papillary/cribriform dominance, nodal spread, recurrence, or rare high-grade transformation. (iyer2021anoverviewon pages 11-12, nonaka2022immunohistochemicalprofileof pages 4-6)

The upstream event is the PRKD alteration; downstream features include altered migration/differentiation, infiltrative growth, perineural invasion, and metastatic competence. Evidence for the exact intermediate substrates and obligate downstream pathways remains largely inferential rather than established through PAC-specific functional screens.

Suggested GO biological-process terms: protein phosphorylation (GO:0006468), intracellular signal transduction (GO:0035556), MAPK cascade (GO:0000165), regulation of cell migration (GO:0030334), epithelial-cell differentiation (GO:0030855), cell adhesion (GO:0007155), and regulation of cell proliferation (GO:0042127).

Suggested cell types: salivary-gland epithelial cell; ductal epithelial cell (CL mapping should be checked against the current Cell Ontology release). No single-cell or spatial-transcriptomic atlas has yet established a PAC-specific cell of origin or tumor microenvironment. No reproducible PAC-specific immune, metabolic, autophagic, or oxidative-stress mechanism is established.

7. Anatomical structures affected

PAC predominantly affects minor salivary gland tissue, with the palate as the characteristic site. It can occur in the buccal mucosa, lip, retromolar region, floor of mouth, tongue/base of tongue, oropharynx, nasopharynx, and sinonasal tract; major-salivary-gland examples are uncommon. Diagnosis is particularly difficult in uncommon sites such as the oropharynx, sinonasal tract, and nasopharynx. (iyer2021anoverviewon pages 11-12, nonaka2022immunohistochemicalprofileof pages 4-6)

Secondary involvement may include adjacent oral soft tissue or bone, peripheral nerves, cervical lymph nodes, and—rarely—distant organs. Lesions are usually unilateral/localized rather than bilateral.

Suggested anatomy terms: UBERON palate (UBERON:0001716), tongue (UBERON:0001723), oral cavity (UBERON:0000165), salivary gland (UBERON:0001044), and minor salivary gland using the most specific current UBERON child term. Relevant compartments include plasma membrane, cytoplasm, and nucleus for signaling and transcriptional consequences; no disease-specific organelle pathology is established.

8. Temporal development

Onset is typically adult and insidious, although rare pediatric or adolescent cases have been reported. The untreated lesion usually enlarges slowly over months or years. Following excision, many patients remain disease-free, but recurrence may be delayed; long-term surveillance is therefore appropriate. There is no recognized premalignant stage, relapsing-remitting pattern, spontaneous remission, or developmental critical period.

Staging follows the AJCC/UICC anatomic staging system for the primary site, not a PAC-specific staging system. Clinically important progression events are increasing primary size/local invasion, positive margins, perineural invasion, nodal metastasis, distant metastasis, and rare high-grade transformation.

9. Inheritance, epidemiology, and population

PAC is rare and represents a small fraction of salivary malignancies, predominantly minor-salivary-gland cancers. A defensible disease-specific incidence per 100,000/year or point prevalence was not available in the retrieved evidence. Published population and institutional series suggest predominance in middle-aged to older adults and commonly a female excess, but precise ratios vary by cohort and should not be treated as universal.

There is no established autosomal-dominant, autosomal-recessive, X-linked, mitochondrial, polygenic, or familial inheritance pattern. PRKD alterations are somatic. Penetrance, carrier frequency, founder effect, consanguinity, genetic anticipation, and germline mosaicism are therefore not applicable under present knowledge. No consistent ethnic or geographic concentration has been demonstrated.

10. Diagnostics

Standard work-up

Clinical examination should document lesion dimensions, mucosal ulceration, fixation, cranial-nerve symptoms, and cervical nodes. MRI is useful for deep extent and perineural disease; contrast-enhanced CT evaluates bone involvement and nodal disease. Ultrasound is useful principally for accessible neck nodes or major-gland lesions. Imaging is not histologically specific.

Fine-needle aspiration or core biopsy may suggest a salivary neoplasm, but PAC’s architectural heterogeneity and overlapping cytology can cause underclassification. Definitive diagnosis generally requires adequate tissue and correlation of architecture, cytology, invasion, immunophenotype, and—when necessary—molecular findings. PAC shows cytologic uniformity, architectural diversity, infiltrative borders, and sometimes myxohyaline matrix. (nonaka2022immunohistochemicalprofileof pages 4-6)

Immunohistochemical and molecular testing

The most useful differential pattern is p63-positive/p40-negative. It was present in 38/39 PACs (97.4%) versus 1/155 adenoid cystic carcinomas in the underlying meta-analysis, with an odds ratio of 801.32 (p<0.00001). The reported ACC percentage of “0.006%” in the extracted source is arithmetically inconsistent with 1/155 (approximately 0.65%); the raw counts should therefore be retained in the knowledge base. (nonaka2022immunohistochemicalprofileof pages 8-10)

PRKD1 E710D testing can be performed by targeted DNA sequencing. Rearrangements are better assessed using break-apart FISH, anchored multiplex RNA sequencing, or another fusion-capable RNA panel. FISH has shown diagnostic utility for PRKD1 alterations, but a negative assay does not exclude PAC because alteration type and fusion partner vary. WES/WGS may identify alterations but are usually unnecessary for a localized, morphologically typical tumor; chromosomal microarray, karyotyping, mitochondrial sequencing, and repeat-expansion testing have no routine role. (iyer2021anoverviewon pages 11-12)

Differential diagnosis

  • Adenoid cystic carcinoma: often more hyperchromatic/biphasic, typically p40-positive in abluminal cells and commonly CD117-positive; MYB/MYBL1 rearrangement supports ACC. PAC’s p63+/p40− phenotype strongly favors PAC. (nonaka2022immunohistochemicalprofileof pages 8-10)
  • Pleomorphic adenoma: circumscription, chondromyxoid stroma, and benign ductal/myoepithelial differentiation favor pleomorphic adenoma.
  • Secretory carcinoma: mammaglobin/GATA3 positivity and an ETV6-family fusion favor secretory carcinoma.
  • Epithelial-myoepithelial carcinoma: overt biphasic ductal and clear myoepithelial layers favor that diagnosis.
  • Clear-cell carcinoma: hyalinizing stroma and EWSR1 rearrangement favor clear-cell carcinoma.
  • Low-grade papillary/cystic salivary tumors and metastatic tumors: require site, morphology, and lineage-specific IHC/molecular correlation.

There is no population screening, liquid-biopsy assay, serum marker, or validated asymptomatic genetic test for PAC.

11. Outcome and prognosis

Conventional PAC generally has favorable disease-specific survival, but the label “low grade” was removed because regional and distant metastases can occur and occasionally become uncontrollable. Cribriform, papillary, solid, high-grade, or transformed morphology; nodal disease; advanced stage; incomplete excision; and recurrent disease are concerning features. (nonaka2022immunohistochemicalprofileof pages 8-10, nonaka2022immunohistochemicalprofileof pages 1-3, iyer2021anoverviewon pages 11-12)

The retrieved full-text evidence did not provide sufficiently robust PAC-specific 5- or 10-year survival, recurrence, nodal-metastasis, distant-metastasis, or disease-specific mortality estimates. Numerical estimates from older small series vary substantially with follow-up duration, inclusion of cribriform tumors, and historical diagnostic criteria. Such figures should not be merged without stratifying conventional PAC from cribriform subtype and high-grade transformation.

Potential long-term morbidity includes recurrent oral tumor, swallowing or speech impairment, palatal fistula/velopharyngeal dysfunction after resection, sensory deficits from nerve involvement, nodal surgery morbidity, and xerostomia or osteoradionecrosis after radiotherapy. PAC-specific validated quality-of-life statistics were not identified.

12. Treatment and real-world implementation

Localized disease

Complete surgical excision with negative margins is the standard treatment. The operation is site dependent and may range from local mucosal excision to partial maxillectomy, tongue-base/oropharyngeal resection, or major-gland surgery. Reconstruction should preserve speech, swallowing, and separation of the oral and nasal cavities. Surgical resection is the principal treatment modality across salivary neoplasms, although disease-specific PAC prospective trials are lacking. (iyer2021anoverviewon pages 11-12)

Suggested NCIT concepts include Surgical Resection, Wide Local Excision, Partial Maxillectomy, Neck Dissection, External Beam Radiation Therapy, Intensity-Modulated Radiation Therapy, and Supportive Care; exact NCIT codes should be validated against the current release.

Elective neck dissection is not routine for a small clinically node-negative conventional PAC. Therapeutic neck dissection is appropriate for confirmed nodal disease. Greater consideration of nodal evaluation is reasonable for cribriform-subtype, tongue-base, advanced, or clinically node-positive tumors.

Postoperative radiotherapy is individualized for positive/unresectable margins, advanced local disease, extensive perineural invasion, nodal disease, recurrent disease, or high-grade transformation. There is no PAC-specific randomized evidence demonstrating an overall-survival advantage for routine adjuvant irradiation after complete excision of a low-risk lesion.

Recurrent or metastatic disease

Resectable local or nodal recurrence is usually managed with salvage surgery, with radiotherapy considered according to prior treatment and risk. For unresectable/metastatic PAC, treatment is extrapolated from broader salivary-carcinoma practice: palliative irradiation, cytotoxic therapy, or biomarker-directed therapy if an independently actionable alteration is found. No PRKD inhibitor, immunotherapy, gene therapy, cell therapy, or RNA therapy is approved specifically for PAC, and PRKD alterations are presently more useful diagnostically than therapeutically.

The clinical-trial search did not identify a clearly PAC-specific interventional study. Enrollment in histology-agnostic or rare-salivary-cancer trials may be considered for advanced disease after comprehensive DNA/RNA profiling, but expected benefit cannot be inferred merely from a PRKD alteration.

Supportive care may include dental evaluation, nutritional support, speech/swallow therapy, prosthodontic obturation or reconstructive rehabilitation, analgesia, xerostomia management, and surveillance for recurrence.

13. Prevention

No primary prevention strategy, vaccine, prophylactic drug, or validated lifestyle intervention is known because no modifiable PAC-specific cause has been established. Population screening and germline cascade screening are not recommended. Secondary prevention consists of prompt evaluation and biopsy of a persistent palatal or other minor-salivary-gland mass. Tertiary prevention includes complete initial excision, management of adverse pathology, oral/dental rehabilitation, and prolonged surveillance for delayed recurrence.

Routine genetic counseling is not indicated solely because a tumor harbors PRKD1 E710D or a PRKD fusion; counseling would become relevant only if personal/family history suggested a separate hereditary cancer syndrome.

14. Other species and natural disease

No well-established naturally occurring veterinary counterpart specifically matching human PRKD-altered PAC was identified. Salivary carcinomas occur in dogs, cats, and other mammals, but histologic resemblance alone does not establish molecular equivalence. There is no zoonotic potential or cross-species transmission. Human taxonomy is Homo sapiens, NCBI Taxon 9606. Orthologues of PRKD-family genes exist in model species, but conservation of the genes does not by itself validate an animal PAC model.

15. Model organisms and experimental systems

No widely accepted PAC-specific genetically engineered mouse, patient-derived xenograft, organoid, or continuously available reference cell line was identified. Generic PRKD gain-of-function systems may study kinase signaling but do not reproduce the salivary architecture, perineural invasion, or prolonged clinical course of PAC. Important future models would include:

  1. salivary epithelial organoids engineered with PRKD1 E710D;
  2. conditional salivary-epithelial PRKD1 knock-in mice;
  3. fusion-positive cribriform-subtype organoids or xenografts; and
  4. spatial/single-cell studies comparing conventional and cribriform PAC.

These are research priorities rather than established resources. The absence of validated models limits causal pathway dissection and preclinical therapeutic testing.

Recent developments, evidence appraisal, and authoritative interpretation

The principal recent advance is refinement of PAC as a molecularly coherent PRKD-family tumor spectrum, accompanied by recognition that conventional mutation-positive PAC and fusion-positive cribriform tumors may differ clinically. The 2022 meta-analysis supplied the most quantitative diagnostic evidence: a broad epithelial/S100/SOX10 phenotype and the highly discriminating p63+/p40− pattern. Its abstract-level conclusion characterizes PAC as a malignant minor-salivary-gland tumor with “morphological diversity, an infiltrative growth pattern, and low metastatic potential”—a useful concise disease definition. (nonaka2022immunohistochemicalprofileof pages 1-3)

Expert interpretation should remain conservative: morphology is primary; IHC is supportive rather than independently definitive; and PRKD testing is most valuable in small biopsies, unusual sites, or difficult differentials. Rare-head-and-neck-tumor reviews emphasize specialist pathology review, molecular analysis where appropriate, and multidisciplinary management. The limited number of prospective studies means that management recommendations rest mostly on retrospective human series and extrapolation from salivary-cancer guidelines, not randomized PAC trials. (iyer2021anoverviewon pages 11-12, nonaka2022immunohistochemicalprofileof pages 4-6)

Key sources and publication details

  1. Nonaka T, Takei H. Immunohistochemical Profile of Polymorphous Adenocarcinoma of Minor Salivary Gland: A Systematic Review and Meta-Analysis. Head and Neck Pathology. Published May 2022;16:980–990. DOI/URL: https://doi.org/10.1007/s12105-022-01453-6. Evidence type: systematic review/meta-analysis of 409 cases. (nonaka2022immunohistochemicalprofileof pages 8-10, nonaka2022immunohistochemicalprofileof pages 1-3, nonaka2022immunohistochemicalprofileof pages 4-6)
  2. Iyer J, et al. An Overview on the Histogenesis and Morphogenesis of Salivary Gland Neoplasms and Evolving Diagnostic Approaches. Cancers. Published August 2021;13:3910. DOI/URL: https://doi.org/10.3390/cancers13153910. Evidence type: peer-reviewed molecular/pathology review. (iyer2021anoverviewon pages 11-12)

PMIDs were not exposed in the retrieved full-text metadata and are therefore not supplied speculatively. Likewise, exact abstract quotations beyond text present in the retrieved evidence have not been fabricated. Primary-study claims that could not be verified in accessible full text have been identified as evidence gaps rather than assigned unsupported statistics.

References

  1. (nonaka2022immunohistochemicalprofileof pages 1-3): Taichiro Nonaka and Hidehiro Takei. Immunohistochemical profile of polymorphous adenocarcinoma of minor salivary gland: a systematic review and meta-analysis. Head and Neck Pathology, 16:980-990, May 2022. URL: https://doi.org/10.1007/s12105-022-01453-6, doi:10.1007/s12105-022-01453-6. This article has 19 citations and is from a peer-reviewed journal.

  2. (iyer2021anoverviewon pages 11-12): Janaki Iyer, Arvind Hariharan, Uyen Minh Nha Cao, Crystal To Tam Mai, Athena Wang, Parisa Khayambashi, Bich Hong Nguyen, Lydia Safi, and Simon D. Tran. An overview on the histogenesis and morphogenesis of salivary gland neoplasms and evolving diagnostic approaches. Cancers, 13:3910, Aug 2021. URL: https://doi.org/10.3390/cancers13153910, doi:10.3390/cancers13153910. This article has 67 citations.

  3. (nonaka2022immunohistochemicalprofileof pages 4-6): Taichiro Nonaka and Hidehiro Takei. Immunohistochemical profile of polymorphous adenocarcinoma of minor salivary gland: a systematic review and meta-analysis. Head and Neck Pathology, 16:980-990, May 2022. URL: https://doi.org/10.1007/s12105-022-01453-6, doi:10.1007/s12105-022-01453-6. This article has 19 citations and is from a peer-reviewed journal.

  4. (nonaka2022immunohistochemicalprofileof pages 8-10): Taichiro Nonaka and Hidehiro Takei. Immunohistochemical profile of polymorphous adenocarcinoma of minor salivary gland: a systematic review and meta-analysis. Head and Neck Pathology, 16:980-990, May 2022. URL: https://doi.org/10.1007/s12105-022-01453-6, doi:10.1007/s12105-022-01453-6. This article has 19 citations and is from a peer-reviewed journal.

Artifacts