Clear cell adenocarcinoma arising in an adenomyoma of the broad ligament

Extrauterine adenomyomas are extremely rare benign tumors of smooth muscles, endometrial glands, and endometrial stroma. Ectopic endometrial glands can undergo malignant change. The ovary is the most common site of malignant change in endometriosis. Cancer arising in extraovarian endometriosis is a rare event with limited cases in the literature. To the best of our knowledge, we present the first case of a clear cell adenocarcinoma arising from foci of ectopic endometrial tissue in an adenomyoma of the broad ligament. It supports the association between endometriomas and clear cell adenocarcinoma. Therefore, patients with a significant history of endometriosis may benefit from close follow-up or definitive surgery.