Subserous uterine adenomyosis mimicking an adnexal mass on sonography

Uterine adenomyosis usually manifests as diffuse disease involving the myometrium and the endometrial-myometrial junction, but it may also manifest as a focal lesion. It is usually only a few millimeters in diameter but may sometimes be larger. We report the case of a 32-year-old woman with a large isolated mass in the uterine wall. Transvaginal sonography demonstrated the cystic nature of the mass and its characteristic hemorrhagic pattern, whereas CT confirmed its uterine origin. The patient underwent laparoscopic resection of the mass, and pathologic examinations led to the diagnosis of adenomyosis.