A 41-year-old woman has a 7 cm solid left ovarian tumour composed of plump spindle cells with abundant lipid-rich cytoplasm. Endometrial biopsy shows disordered proliferative endometrium with simple hyperplasia. Which tumour is she most likely to have?

• A Ovarian fibroma
• B Fibrosarcoma
• C Sclerosing stromal tumour
• D Thecoma ✓

Explanation

Thecomas are benign sex cord-stromal tumours whose theca cells are functionally active and secrete oestradiol, producing endometrial hyperplasia and abnormal uterine bleeding, with a recognised increased risk of concurrent endometrial carcinoma. The lipid content gives the cytoplasm its pale vacuolated look. An ovarian fibroma is histologically similar but is hormonally inert, presenting instead as an asymptomatic mass or with Meigs syndrome, which is why option A fails to explain the endometrial findings.

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

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