Definition/General
Introduction:
Ovarian endometrioid carcinoma is an epithelial tumor resembling endometrial adenocarcinoma
It accounts for 10-15% of all ovarian cancers
It arises from ovarian endometriosis or ovarian surface epithelium
It demonstrates glandular architecture similar to uterine endometrioid carcinoma.
Origin:
Originates from ovarian endometriosis in 40-50% of cases
May arise from ovarian surface epithelium with endometrioid differentiation
The neoplastic transformation involves ARID1A mutations commonly
It progresses through atypical endometriosis-carcinoma sequence
Lynch syndrome association in some cases.
Classification:
Classified using FIGO grading system (Grade 1-3)
Grade 1: well-differentiated with >95% glandular pattern
Grade 2: moderately differentiated with 50-95% glandular pattern
Grade 3: poorly differentiated with <50% glandular pattern
Squamous differentiation common.
Epidemiology:
Peak incidence in 5th-6th decades
Strong association with endometriosis (40-50% cases)
Lynch syndrome association (5-10%)
Better prognosis than serous carcinoma
Often presents at early stage
Indian population shows similar patterns to Western countries.
Clinical Features
Presentation:
Pelvic mass (most common presentation)
Abdominal pain related to endometriosis
History of endometriosis in 40-50% cases
CA-125 elevation variable
Often presents at Stage I-II.
Symptoms:
Pelvic or abdominal pain (60% cases)
Menstrual irregularities (if ovarian function affected)
Dyspareunia (associated endometriosis)
Abdominal distension (large tumors)
Infertility history (endometriosis-related).
Risk Factors:
Endometriosis (strongest risk factor)
Lynch syndrome (hereditary cases)
Family history of colorectal/endometrial cancer
Nulliparity
Late menopause
Unopposed estrogen exposure.
Screening:
No specific screening available
CA-125 may be elevated
Imaging shows complex adnexal mass
Lynch syndrome screening in appropriate cases
Endometriosis surveillance controversial.
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Gross Description
Appearance:
Solid and cystic mass with hemorrhagic areas
Chocolate-colored cysts (endometriotic component)
Soft, friable consistency
Necrosis in high-grade tumors
Associated endometriotic cysts common.
Characteristics:
Gray-white to tan solid areas
Dark brown fluid in cystic areas (old blood)
Thick, irregular cyst walls
Papillary projections uncommon
Calcifications rare.
Size Location:
Variable size (3-20 cm, average 10 cm)
Unilateral in 70-80% cases
Left ovary more commonly affected
Bilateral involvement in 20-30%
Peritoneal implants less common than serous.
Multifocality:
Synchronous endometrial carcinoma in 15-20% cases
Deep infiltrating endometriosis may be present
Peritoneal disease uncommon at presentation
Lymph node involvement correlates with grade and stage.
Microscopic Description
Histological Features:
Glandular architecture resembling endometrial adenocarcinoma
Squamous metaplasia in 50% cases
Endometriotic stroma may be present
Cribriform pattern common
Solid areas in high-grade tumors.
Cellular Characteristics:
Epithelial cells with moderate nuclear pleomorphism
Prominent nucleoli
Cytoplasm eosinophilic to amphophilic
Squamous pearls may be present
Mitotic activity varies with grade.
Architectural Patterns:
Glandular pattern predominant
Cribriform pattern
Solid pattern (high-grade)
Squamous differentiation
Secretory variant (rare)
Oxyphilic variant (rare).
Grading Criteria:
FIGO grading system: Grade 1 (>95% glandular)
Grade 2 (50-95% glandular)
Grade 3 (<50% glandular)
Nuclear grade also considered
Squamous component not counted in grading.
Immunohistochemistry
Positive Markers:
PAX8 (90-95%)
ER (80-90%)
PR (70-80%)
CK7 (100%)
Vimentin (90%)
CA-125 (variable)
β-catenin (nuclear in some cases).
Negative Markers:
WT1 (negative)
CK20 (negative)
CDX2 (negative)
TTF1 (negative)
Inhibin (negative)
Calretinin (negative).
Diagnostic Utility:
Essential for distinguishing from metastatic endometrial carcinoma
PAX8 and ER/PR positivity support Müllerian origin
β-catenin nuclear staining suggests CTNNB1 mutation
Lynch syndrome markers (MLH1, MSH2, MSH6, PMS2) important.
Molecular Subtypes:
Lynch syndrome-associated (MSI-high)
ARID1A-mutated (endometriosis-associated)
CTNNB1-mutated (β-catenin nuclear)
PIK3CA-mutated subtype.
Molecular/Genetic
Genetic Mutations:
ARID1A mutations (40-50%)
PIK3CA mutations (30-40%)
CTNNB1 mutations (20-30%)
PTEN mutations (20%)
TP53 mutations (high-grade)
Mismatch repair genes (Lynch syndrome).
Molecular Markers:
ARID1A loss of expression
β-catenin nuclear accumulation
PTEN loss
p53 overexpression (high-grade)
Microsatellite instability (Lynch cases)
PD-L1 expression variable.
Prognostic Significance:
Grade most important prognostic factor
Stage at presentation crucial
Lynch syndrome may indicate better prognosis
β-catenin mutations associated with better outcome
ARID1A loss prognostic significance unclear.
Therapeutic Targets:
Hormone therapy (ER/PR positive cases)
mTOR inhibitors (PIK3CA/PTEN mutations)
Immunotherapy (MSI-high cases)
PARP inhibitors (investigational)
β-catenin pathway inhibitors (investigational).
Differential Diagnosis
Similar Entities:
Metastatic endometrial carcinoma (most important)
Primary tubal carcinoma
Serous carcinoma (with endometrioid features)
Clear cell carcinoma
Transitional cell carcinoma.
Distinguishing Features:
Primary ovarian: associated endometriosis, often unilateral
Metastatic endometrial: bilateral, lymphovascular invasion, clinical history
Serous: WT1+, p53 mutated pattern
Clear cell: clear cells, HNF1β+
Transitional: transitional morphology.
Diagnostic Challenges:
Distinguishing primary ovarian from metastatic endometrial
Identifying synchronous primaries
Grading heterogeneous tumors
Lynch syndrome screening indications
Endometriosis-associated vs de novo.
Rare Variants:
Secretory variant (progesterone-like changes)
Oxyphilic variant (oncocytic features)
Endometrioid carcinoma with squamous differentiation
Adenosquamous carcinoma.
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
Endometrioid carcinoma with [% squamous differentiation] squamous differentiation
Classification and Grade
Endometrioid carcinoma, FIGO Grade [1/2/3]
Histological Features
Shows glandular architecture with squamous differentiation and associated endometriosis
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: PAX8 (+), ER (+), PR (+), WT1 (-), β-catenin ([nuclear/membranous])
Lynch syndrome markers: MLH1, MSH2, MSH6, PMS2 [results]
Endometriosis: [present/absent] in adjacent ovarian tissue
Prognostic Factors
Grade: [1/2/3]; Stage: [FIGO stage]; Associated endometriosis: [present/absent]
Final Diagnosis
Ovarian endometrioid carcinoma, FIGO Grade [X], Stage [X], arising in association with endometriosis