A 47-year-old woman with a long history of dysmenorrhoea undergoes surgery for a pelvic mass. The ovarian tumour shows sheets of hobnail cells with clear cytoplasm lining glandular and cystic spaces, arising adjacent to an area of endometriosis. Which subtype of epithelial ovarian cancer is this, and what molecular feature supports its distinct pathway?

• A High-grade serous carcinoma, TP53 mutation
• B Clear cell carcinoma, ARID1A mutation ✓
• C Endometrioid carcinoma, PTEN mutation
• D Low-grade serous carcinoma, KRAS mutation

Explanation

Clear cell carcinoma characteristically arises from endometriotic epithelium, displays hobnail cells with clear cytoplasm, and carries frequent ARID1B mutations, placing it in the endometriosis-associated pathway alongside endometrioid carcinoma. High-grade serous carcinoma arises from fallopian tube fimbriae via TP53 mutation and p53 signature lesions. While endometrioid tumours share the endometriosis pathway, their morphology is glandular rather than clear and hobnail.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.