Which epithelial ovarian tumor is most commonly associated with endometriosis and typically presents as a unilateral, solid mass with hemorrhagic cyst formation?

Explanation

## Clear Cell Carcinoma of the Ovary: Endometriosis Association **Key Point:** Clear cell carcinoma (CCC) is an epithelial ovarian malignancy strongly associated with endometriosis and typically presents as a unilateral, solid mass with hemorrhagic features. ### Epidemiology and Risk Factors - **Endometriosis association:** Present in 30–50% of cases (highest among epithelial tumors) - **Age of presentation:** Typically 40–60 years - **Laterality:** Usually unilateral - **Geographic variation:** More common in East Asia and Japan ### Pathological Features | Feature | Description | |---------|-------------| | **Gross appearance** | Solid, unilateral mass with hemorrhagic cyst | | **Histology** | Cells with clear cytoplasm (glycogen-rich), hobnail cells | | **Growth pattern** | Solid sheets, tubulocystic, or papillary | | **Nuclear features** | High-grade nuclei, brisk mitotic activity | | **Immunohistochemistry** | Positive for HNF-1β, PAX8; negative for WT1 | **High-Yield:** Clear cell carcinoma is one of the most aggressive epithelial ovarian cancers, with stage I disease having worse prognosis than serous or mucinous adenocarcinomas. It is chemotherapy-resistant (platinum-refractory in ~30% of cases). ### Clinical Presentation - Abdominal pain or pelvic mass - Often presents at advanced stage - Associated history of endometriosis - May have elevated CA-125 **Mnemonic:** **CLEAR** — **C**lear cytoplasm, **L**ow chemotherapy response, **E**ndometriosis-associated, **A**ggressive behavior, **R**are but high-grade malignancy. **Clinical Pearl:** The presence of endometriosis in an ovarian mass should raise suspicion for clear cell or endometrioid carcinoma, not benign epithelial tumors.