Atypical polypoid adenomyoma (APA) is considered to be a rare, benign form of a polypoid mass that exhibits glandular and squamous epithelial cell proliferation with varying degrees of atypia in association with cellular smooth muscle stroma. More frequently it manifests during the reproductive and premenopausal age with a reported mean age of 40 years. The published series indicates an average risk of endometrial carcinoma of 8.8% in women with a history of polypoid adenomyoma. The differential diagnosis of APA includes complex endometrial hyperplasia with atypia, invasive adenocarcinoma, adenofibroma, adenosarcoma and carcinosarcoma. The recognition of these unusual benign uterine tumors is very important, because they can easily be misdiagnosed. Treatment may vary depending on the patient's age, her desire to preserve fertility and the severity of her symptoms. We present a case of an infertile 39-year-old woman with an incidental diagnosis of APA.