| Diagnostic Category | Specific Test/Method | Findings/Markers | Clinical Utility | References |
|---|---|---|---|---|
| Histopathologic classification | WHO 2020 histotype classification | Ovarian carcinoma is classified into principal histotypes including mucinous carcinoma; accurate histotyping integrates morphology, immunophenotype, and molecular features | Establishes that mucinous carcinoma is a distinct ovarian carcinoma type requiring subtype-specific diagnosis and management | (pqac-00000001, pqac-00000002) |
| Histopathologic subtyping | Growth pattern assessment on resection specimen | Mucinous ovarian carcinoma is subclassified into **expansile** and **infiltrative** invasion patterns; distinction is clinically important particularly in stage I disease | Helps risk stratification and may affect decisions about staging lymphadenectomy and adjuvant chemotherapy | (pqac-00000003) |
| Gross pathology / surgical pathology | Macroscopic tumor assessment | Primary mucinous ovarian carcinoma is typically a **large, multilocular**, usually **unilateral** ovarian mass; tumor size **>10 cm** favors primary ovarian origin | Supports distinction of primary ovarian tumor from metastatic mucinous tumor to the ovary | (pqac-00000003, pqac-00000011) |
| Histopathology for primary vs metastatic differential | Routine microscopic examination | Features favoring **primary mucinous ovarian carcinoma**: benign or borderline components, unilateral mass, normal appendix, no capsular/serosal implants, absence of extracellular mucin; features favoring **metastatic mucinous tumor**: ovarian surface/hilum involvement, infiltrative stromal invasion, extracellular mucin, widespread signet-ring cells | Core diagnostic step to distinguish primary ovarian mucinous carcinoma from gastrointestinal, appendiceal, breast, or cervical metastases | (pqac-00000011) |
| Histopathology / mucin pattern | Intracellular vs extracellular mucin distribution | Primary mucinous ovarian carcinoma is often characterized by **high intracellular mucin** and relatively **low extracellular mucin**; metastatic mucinous tumors more often show abundant extracellular mucin | Useful adjunctive morphologic clue in differential diagnosis; extracellular mucin may also correlate with poorer prognosis in primary disease | (pqac-00000010, pqac-00000011) |
| Immunohistochemistry | CK7 / CK20 / CDX2 / PAX8 panel | Typical profile for mucinous ovarian carcinoma: **CK7 positive**, **CK20 and CDX2 variable**, **PAX8 variable positive**, **SATB2 negative**; strong **PAX8 positivity** supports ovarian origin | Widely used first-line IHC panel to separate primary ovarian mucinous carcinoma from lower GI and other extra-ovarian mucinous carcinomas | (pqac-00000004, pqac-00000011) |
| Immunohistochemistry | SATB2 with CK7 | Combination of **CK7 and SATB2** can distinguish lower gastrointestinal tumors from primary ovarian mucinous tumors with high accuracy; lower GI metastases tend to be SATB2 positive | Improves diagnostic specificity for metastases from colorectum/appendix | (pqac-00000010, pqac-00000011) |
| Immunohistochemistry | Claudin 18.2 / PAX8 / SATB2 panel | Reported patterns: **primary mucinous ovarian carcinoma** often **claudin18.2+/PAX8+/SATB2-**; upper GI metastases **claudin18.2+/PAX8-/SATB2-**; lower GI metastases **claudin18.2-/PAX8-/SATB2+** | Useful extended panel when routine CK7/CK20/CDX2/PAX8 results are equivocal | (pqac-00000010, pqac-00000011) |
| Immunohistochemistry | MUC1, MUC2, MUC5AC, MUC6 | Mucin markers contribute to differential diagnosis: **MUC2** and **MUC6** may help identify primary mucinous ovarian carcinoma; **MUC5AC** may help distinguish colorectal cancer from primary ovarian mucinous carcinoma but is less useful for pancreatic metastases; **MUC1** has been proposed as a novel discriminator between primary and metastatic mucinous ovarian tumors | Ancillary diagnostic markers, especially useful when combined with standard epithelial and lineage markers | (pqac-00000010, pqac-00000011) |
| Immunohistochemistry | MUC2 and MUC5AC comparison | In one summarized comparison, **MUC2 positivity** was reported in colorectal cancers but not mucinous ovarian cancers, whereas **MUC5AC** was much more frequent in mucinous ovarian cancer | Helps separate colorectal metastasis from primary ovarian mucinous carcinoma | (pqac-00000010) |
| Histotype-oriented IHC | Four-marker ovarian carcinoma panel | A four-marker panel (**WT1 / p53 / napsin A / PR**) distinguishes the five principal ovarian carcinoma histotypes with high accuracy; mucinous carcinoma is identified largely through exclusion plus morphology and lineage markers rather than a unique single marker | Useful for overall ovarian carcinoma subclassification when the diagnosis is uncertain among ovarian histotypes | (pqac-00000001) |
| Serum biomarker | CA125 | CA125 has **lower sensitivity in mucinous ovarian carcinoma** than in serous carcinoma; one recent review notes abnormal CA125 in only about **69%** of mucinous tumors, often at lower absolute levels | Limited as a stand-alone diagnostic marker; lower performance underscores need for imaging, pathology, and additional biomarkers | (pqac-00000006) |
| Serum / emerging biomarker | MUC13 | MUC13 has been proposed as a candidate biomarker that may complement CA125 in detecting non-serous ovarian carcinomas including mucinous tumors | Potential adjunct biomarker for non-serous subtype detection, though not yet standard of care | (pqac-00000006, pqac-00000011) |
| Imaging | Ultrasound / CT / MRI | Imaging can detect an adnexal mass and assess size, multilocularity, laterality, and spread; however, recent reviews note persistent diagnostic difficulty in reliably classifying mucinous tumors preoperatively | Preoperative evaluation of extent of disease and surgical planning; limited specificity for distinguishing primary from metastatic mucinous tumors without pathology | (pqac-00000003) |
| Preoperative assessment | Clinical evaluation plus imaging plus pathology correlation | Because many tumors historically labeled ovarian mucinous are actually metastases, diagnosis requires correlation of ovarian findings with gastrointestinal/appendiceal evaluation and clinicopathologic review | Avoids misclassification and inappropriate ovarian-cancer-directed treatment of metastatic GI cancer | (pqac-00000004, pqac-00000011) |
| Molecular testing | KRAS / ERBB2(HER2) / TP53 / CDKN2A profiling | Common alterations in mucinous ovarian carcinoma include **KRAS** mutations, **ERBB2 amplification**, **TP53** mutation, and **CDKN2A** loss/inactivation; absence of KRAS or HER2 in some cases may suggest unusual precursors such as teratoma-associated tumors | Supports diagnosis, biological classification, prognostic assessment, and selection for targeted therapy | (pqac-00000002, pqac-00000004, pqac-00000006, pqac-00000007, pqac-00000015) |
| Molecular diagnostics in differential diagnosis | Correlation of mutation profile with morphology | Molecular alterations may complement histology and IHC in distinguishing primary mucinous ovarian tumors from metastases and from other ovarian epithelial subtypes | Useful adjunct where morphology and immunophenotype are overlapping or ambiguous | (pqac-00000004) |
| Post-operative definitive diagnosis | Integrated morphologic + IHC diagnosis on resection specimen | Recent reviews emphasize that definitive diagnosis is often made **post-operatively** after full histopathologic examination with immunohistochemical markers because of strong overlap with metastatic mucinous lesions | Current gold standard for final diagnosis of primary ovarian mucinous carcinoma | (pqac-00000004) |


*Table: This table summarizes the main diagnostic approaches for ovarian mucinous carcinoma, including pathology, immunohistochemistry, biomarkers, imaging, and molecular testing. It is especially useful for distinguishing primary ovarian mucinous carcinoma from metastatic gastrointestinal mucinous tumors.*