Regarding epithelial ovarian tumors, all of the following statements are correct EXCEPT:

## Epithelial Ovarian Tumors — Comparative Features **Key Point:** Mucinous tumors are characteristically UNILATERAL in 95% of cases, whereas serous tumors show bilateral involvement in 15–20% of cases. The distractor statement reverses this critical epidemiological fact. ### Correct Statements Explained **Serous Tumors (Most Common)** - Account for ~40% of epithelial ovarian tumors - Show bilateral involvement in 15–20% of cases - Include benign, borderline, and malignant variants - Often present at advanced stage when malignant **Mucinous Tumors (Second Most Common)** - Account for ~20% of epithelial ovarian tumors - **Unilateral in >95% of cases** — this is a defining feature - Bilateral mucinous tumors should raise suspicion for metastatic disease (e.g., appendiceal primary) - Better prognosis than serous when confined to ovary **Clear Cell Carcinomas** - Strong association with endometriosis (present in 30–50% of cases) - Aggressive behavior with poor 5-year survival (~50%) - More common in Asian populations - Often present at advanced stage **Brenner Tumors** - Arise from coelomic epithelium (transitional epithelium) - Typically benign (>90%) - Account for ~2–3% of epithelial ovarian tumors - Often incidental finding; rarely symptomatic | Tumor Type | Frequency | Bilateral | Prognosis | Key Association | | --- | --- | --- | --- | --- | | Serous | 40% | 15–20% | Variable | — | | Mucinous | 20% | <5% | Better (early stage) | — | | Endometrioid | 10% | <5% | Intermediate | Endometriosis | | Clear cell | 10% | <5% | Poor | Endometriosis | | Brenner | 2–3% | Rare | Excellent (benign) | — | **High-Yield:** Unilateral mucinous tumor = ovarian primary. Bilateral mucinous tumor = metastatic (appendix, colon) until proven otherwise. **Clinical Pearl:** The presence of endometriosis in a patient with ovarian cancer should prompt consideration of clear cell or endometrioid histology, both of which carry worse prognosis than serous tumors of equivalent stage.