What is the histology of mucinous tumors of the ovary?

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Histology of Mucinous Ovarian Tumors

Mucinous ovarian neoplasms are composed of multiple cysts lined by mucinous epithelium that frequently resembles gastrointestinal-type epithelium, with the majority demonstrating gastric superficial/foveolar cell differentiation. 1

Microscopic Architecture

Basic Histologic Features

  • Cystic structures lined by columnar mucinous epithelial cells with abundant intracytoplasmic mucin, creating a characteristic appearance similar to gastric or intestinal epithelium 2, 1
  • Multiloculated cystic architecture with variable mucin content in different loculi, accounting for the heterogeneous appearance on imaging 2
  • Gastrointestinal-type differentiation is the predominant pattern, with cells resembling gastric superficial/foveolar cells, pyloric gland cells, intestinal columnar cells, or goblet cells 1, 3

Immunohistochemical Profile

  • M1 mucin antigen is expressed in 95% of mucinous ovarian tumors, serving as a highly sensitive marker of gastric-type differentiation 1
  • Cathepsin E is present in 92% of cases, further supporting gastric superficial/foveolar cell lineage 1
  • Periodic acid-concanavalin A-reactive mucin or pepsinogen II (markers of gastric mucus neck and pyloric gland cells) are found in 79% of tumors 1
  • CAR-5 and M3SI (intestinal mucin markers) are significantly more common in malignant tumors compared to benign and borderline lesions (P < 0.001) 1
  • DU-PAN-2 (pancreatobiliary duct marker) is expressed in 70% of cases 1

Spectrum of Histologic Subtypes

Benign Mucinous Cystadenomas

  • Simple cysts lined by bland mucinous epithelium without architectural complexity or cytologic atypia 3, 4
  • Account for approximately 80% of all mucinous ovarian neoplasms 2

Borderline Mucinous Tumors (Intestinal Type)

  • Epithelial stratification and architectural complexity without stromal invasion 3, 4
  • May contain areas of intraepithelial carcinoma characterized by marked nuclear atypia in non-invasive foci 5
  • Represent 16-17% of mucinous ovarian neoplasms 2
  • Critical sampling requirement: at least 1 block per centimeter of maximum tumor diameter for neoplasms ≤10 cm, and 2 sections per centimeter for larger tumors, due to frequent intratumoral heterogeneity 5

Invasive Mucinous Carcinomas

Expansile (Confluent/Non-Destructive) Pattern

  • Architecturally complex glands, cysts, or papillae lined by atypical epithelium with minimal to no intervening stroma 5
  • Generally stage I with excellent prognosis 3, 4
  • Requires arbitrary minimum size criterion for diagnosis due to difficulty distinguishing from extensive noninvasive carcinoma 4

Infiltrative (Destructive) Pattern

  • Haphazardly arranged glands, tubules, nests, and cords of malignant cells infiltrating stroma 5
  • Associated desmoplastic, inflammatory, or edematous stromal response 5
  • More aggressive behavior, accounting for most high-stage mucinous tumors and tumor-related deaths 3, 4
  • Microinvasive infiltrative carcinomas (minimal stromal invasion) have excellent prognosis when stage I 3

Critical Histologic Heterogeneity

Mucinous ovarian neoplasms exhibit considerable intratumoral heterogeneity with admixture of benign, borderline, and malignant areas within the same tumor. 5 This heterogeneity:

  • Displays more histological variation than serous carcinomas 5
  • Necessitates extensive sampling to identify foci of microinvasion or invasion in borderline tumors 5
  • Requires additional sampling when intraepithelial carcinoma or microinvasion are identified in initial sections, as these features increase likelihood of harboring invasive foci 5

Differential Diagnosis Considerations

Primary vs. Metastatic Disease

  • Unilateral mucinous carcinomas ≥10 cm are more likely primary than metastatic 5
  • PAX8 immunostaining is positive in primary ovarian tumors and negative in metastatic gastrointestinal tumors 6, 7
  • CK7, PAX8, CA125 are positive in primary ovarian tumors, while CK20, CEA, CDX2 are positive in colorectal metastases 7

Common Diagnostic Pitfalls

  • Inadequate sampling is the most critical error, as it may miss invasive foci in borderline tumors or fail to identify the most aggressive component in carcinomas 5, 4
  • Failure to examine the appendix in cases with "pseudomyxoma peritonei" can lead to misdiagnosis of metastatic appendiceal tumors as primary ovarian neoplasms 3
  • Misclassification of metastatic mucinous tumors as primary ovarian neoplasms, particularly when bilateral, <10 cm, or high stage 4

References

2
Research

Mucinous Neoplasms of the Ovary: Radiologic-Pathologic Correlation.

Radiographics : a review publication of the Radiological Society of North America, Inc, 2019

4
Research

Mucinous tumors of the ovary: a review.

International journal of gynecological pathology : official journal of the International Society of Gynecological Pathologists, 2005

5
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

6
Guideline

Management of Mucinous Ovarian Carcinoma

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

7
Guideline

Ovarian Metastasis Diagnosis and Management

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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