## Histological Classification of Epithelial Ovarian Cancer **Key Point:** Serous cystadenocarcinoma is the most common histological type of epithelial ovarian cancer, accounting for approximately 40–50% of all epithelial ovarian malignancies. ### Frequency Distribution of Epithelial Ovarian Cancers | Histological Type | Frequency | Key Features | |---|---|---| | **Serous** | 40–50% | Most common; papillary architecture; often bilateral (30%); BRCA1/2 association | | **Mucinous** | 10–15% | Second most common; cystic appearance; often unilateral; better prognosis | | **Endometrioid** | 10% | Associated with endometriosis; earlier stage at diagnosis | | **Clear cell** | 5–10% | Associated with endometriosis; chemotherapy-resistant; poor prognosis | | **Brenner** | <5% | Rare; usually benign; malignant form very uncommon | **High-Yield:** Serous tumors are the most common and most aggressive form, with high rates of advanced-stage disease at presentation and higher mortality compared to mucinous and endometrioid types. **Clinical Pearl:** Serous ovarian cancers have a strong association with **BRCA1 and BRCA2 mutations**, making genetic counseling and testing essential in affected families. ### Why Serous Is Most Common 1. Arises from surface epithelium (coelomic origin) 2. Papillary growth pattern facilitates peritoneal spread 3. Often presents at advanced stage (FIGO III–IV) 4. Accounts for the majority of high-grade serous ovarian carcinomas (HGSOC) **Mnemonic:** **SMECB** — Serous (most common), Mucinous (second), Endometrioid, Clear cell, Brenner (least common) — in order of frequency. [cite:Robbins 10e Ch 22]
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