[A case of uterine cystic adenomatoid tumor mimicking malignant ovarian tumor on MR imaging].

We report a case of adenomatoid tumor of the uterus. MR images demonstrated a cystic mass with septae attached to the posterior wall of the uterus, making it difficult to distinguish from a malignant ovarian tumor. However, normal bilateral ovaries and beak sign continuing to the uterus were detected on MR images, enabling us to distinguish the cystic mass from a malignant ovarian tumor. Laparotomy demonstrated a subserosal mass of the uterine fundus. The macroscopic specimen showed a multilocular cystic mass, while the microscopic specimen showed cystic spaces lined with flattened and cuboidal cells admixed with smooth muscle, confirming the diagnosis of adenomatoid tumor of the uterus.