Definition/General
Introduction:
Ovarian mucinous carcinoma is a rare epithelial tumor of the ovary
It accounts for 3-5% of all ovarian cancers
It arises from ovarian surface epithelium with mucinous differentiation
It demonstrates glandular architecture with mucin production.
Origin:
Originates from ovarian surface epithelium or inclusions cysts
May arise from pre-existing mucinous cystadenoma or borderline tumor
The neoplastic transformation involves KRAS mutations commonly
It progresses through adenoma-borderline-carcinoma sequence
Primary ovarian origin must be distinguished from metastatic mucinous carcinoma.
Classification:
Classified as intestinal type (most common) or endocervical type
Intestinal type resembles colorectal adenocarcinoma
Endocervical type resembles cervical adenocarcinoma
Primary vs metastatic distinction crucial
FIGO grading system used (Grade 1-3).
Epidemiology:
Peak incidence in 4th-5th decades (younger than serous)
Risk factors less well defined
No association with BRCA mutations
More common in Asian populations
Better prognosis than serous carcinoma when truly primary
Indian population shows relatively higher incidence compared to Western countries.
Clinical Features
Presentation:
Unilateral pelvic mass (80-90% cases)
Abdominal distension due to large tumor size
Pelvic pain or pressure
CA-125 often normal or mildly elevated
CEA may be elevated
Usually presents at early stage (I-II).
Symptoms:
Abdominal fullness and discomfort (70% cases)
Urinary symptoms due to mass effect (40% cases)
Change in bowel habits (30% cases)
Weight gain due to tumor mass
Rarely presents with acute abdomen (torsion, rupture)
Constitutional symptoms uncommon.
Risk Factors:
Age 40-60 years (peak incidence)
No clear hereditary pattern
Possible association with smoking
Nulliparity (weak association)
No BRCA association
Previous ovarian cysts (theoretical risk).
Screening:
No specific screening available
CA-125 not reliable (often normal)
CEA, CA 19-9 may be elevated
Imaging shows complex cystic mass
Frozen section important for intraoperative diagnosis.
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Gross Description
Appearance:
Large, multilocular cystic mass with thick viscous mucin
Unilateral in 80-90% cases
Smooth external surface (if confined to ovary)
Cut surface shows mucin-filled cysts
Areas of solid nodules suggest invasive component.
Characteristics:
Gray-white to tan solid areas
Gelatinous mucin fills cyst cavities
Thick cyst walls with papillary projections
Necrosis in high-grade tumors
Calcifications uncommon.
Size Location:
Usually very large (10-30 cm, can be >40 cm)
Unilateral in majority of cases
Right ovary slightly more common
Bilateral involvement suggests metastatic disease
Surface involvement may indicate spread.
Multifocality:
Usually unifocal when primary
Bilateral disease raises suspicion for metastases
Peritoneal implants uncommon in early-stage primary
Pseudomyxoma peritonei rare complication
Appendiceal primary must be excluded if bilateral.
Microscopic Description
Histological Features:
Glandular architecture with mucin-containing cells
Intestinal type shows goblet cells and Paneth cells
Cribriform pattern common
Mucin lakes with floating tumor cells
Desmoplastic stroma in invasive areas.
Cellular Characteristics:
Epithelial cells with abundant intracytoplasmic mucin
Goblet cell morphology (intestinal type)
Nuclear pleomorphism varies with grade
Prominent nucleoli in high-grade tumors
Mitotic activity correlates with grade.
Architectural Patterns:
Glandular pattern predominant
Villoglandular pattern
Solid pattern (high-grade areas)
Signet ring cell pattern (rare)
Micropapillary pattern (associated with poor prognosis).
Grading Criteria:
Three-tier grading system: Grade 1 (well-differentiated, <5% solid areas)
Grade 2 (moderately differentiated, 5-50% solid areas)
Grade 3 (poorly differentiated, >50% solid areas)
Nuclear grade and mitotic activity also considered.
Immunohistochemistry
Positive Markers:
CK7 (variable, 50-70%)
CK20 (positive, 80-90%)
CDX2 (positive, intestinal type)
CEA (positive)
CA 19-9 (positive)
MUC2 (intestinal type)
Villin (intestinal type).
Negative Markers:
PAX8 (negative or weak)
WT1 (negative)
p53 (wild-type pattern)
ER/PR (negative)
Inhibin (negative)
Calretinin (negative).
Diagnostic Utility:
Essential for distinguishing from metastatic colorectal carcinoma
CK7+/CK20+ pattern supports ovarian primary
PAX8 negativity distinguishes from other ovarian carcinomas
CDX2 positivity indicates intestinal differentiation
Profile helps exclude appendiceal primary.
Molecular Subtypes:
Intestinal type (CK20+, CDX2+, MUC2+)
Endocervical type (CK7+, MUC6+)
KRAS-mutated subtype (better prognosis)
Microsatellite stable (majority).
Molecular/Genetic
Genetic Mutations:
KRAS mutations (60-70% cases)
TP53 mutations (less common than serous)
PIK3CA mutations (20-30%)
ARID1A mutations (10-20%)
BRAF mutations (rare)
APC mutations (rare).
Molecular Markers:
KRAS overexpression
p53 wild-type pattern (majority)
β-catenin membranous staining
MSI testing usually stable
HER2 amplification rare
PD-L1 expression variable.
Prognostic Significance:
KRAS mutations associated with better prognosis
p53 wild-type indicates better outcome
Grade most important prognostic factor
Stage at presentation crucial
Bilateral disease suggests poor prognosis.
Therapeutic Targets:
Limited targeted options compared to serous carcinoma
MEK inhibitors (KRAS-mutated cases, investigational)
Anti-angiogenic agents
Immunotherapy (limited efficacy)
Conventional chemotherapy mainstay.
Differential Diagnosis
Similar Entities:
Metastatic colorectal carcinoma (most important differential)
Metastatic appendiceal carcinoma
Metastatic pancreatic carcinoma
Mucinous borderline tumor
Endometrioid carcinoma with mucinous features.
Distinguishing Features:
Primary ovarian: Unilateral, large size, CK7+
Metastatic colorectal: bilateral, smaller, CK7-, better CDX2 expression
Metastatic appendiceal: pseudomyxoma peritonei pattern
Borderline: no stromal invasion
Endometrioid: PAX8+, squamous elements.
Diagnostic Challenges:
Distinguishing primary from metastatic mucinous carcinoma
Identifying occult appendiceal primary
Assessing stromal invasion in borderline areas
Frozen section limitations
Bilateral disease significance.
Rare Variants:
Mucinous carcinoma with anaplastic features
Mucinous carcinoma with sarcomatoid features
Mucinous carcinoma with signet ring cells
Mucinous carcinoma with neuroendocrine features.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
[laterality] salpingo-oophorectomy, measuring [size] cm
Diagnosis
Mucinous carcinoma, [intestinal/endocervical] type
Classification and Grade
Primary ovarian mucinous carcinoma, FIGO Grade [1/2/3]
Histological Features
Shows glandular architecture with mucin-containing cells and [specific features]
Size and Extent
Tumor size: [X] cm, [unilateral/bilateral], FIGO Stage: [stage]
Lymphovascular Invasion
Lymphovascular invasion: [present/absent]
Lymph Node Status
Pelvic lymph nodes: [X] negative out of [X] examined
Special Studies
IHC: CK7 ([result]), CK20 (+), CDX2 (+), PAX8 (-), CEA (+)
Molecular: KRAS [result] if performed
Primary vs metastatic assessment: Favors primary ovarian origin
Prognostic Factors
Grade: [1/2/3]; Stage: [FIGO stage]; Laterality: [unilateral/bilateral]
Final Diagnosis
Primary ovarian mucinous carcinoma, [intestinal/endocervical] type, FIGO Grade [X], Stage [X]