Primary sex cord-like variant of endometrioid adenocarcinoma arising from endometriosis.

Endometriosis, a relatively common disease generally affecting women in the reproductive age group, is mostly found in the pelvic organs. Although endometriosis is a benign disease, some malignant tumors have been reported to develop in endometriotic lesions, most commonly in the ovary. The relationship between endometriosis and malignancy is not well known, but the majority of endometriosis-associated ovarian malignancies are usually endometrioid adenocarcinomas and clear cell carcinomas. The sex cord-like variant of endometrioid adenocarcinoma is a rare tumor that histologically closely resembles the sex cord-stromal tumor. Despite its rarity, the correct histological diagnosis of the sex cord-like variant of endometrioid adenocarcinoma is crucial to avoid misdiagnosis of a less aggressive tumor. We here report a 53-year-old woman who was diagnosed as having this very rare subtype of endometroid adenocarcinoma curiously arising from an endometriotic lesion at the site of previous salpingo-oophorectomy. The tumor was diagnosed based on light microscopy and immunohistochemistry.