Placental site trophoblastic tumor (PSTT) is the rarest form of gestational trophoblastic diseases. We report a 40-year-old woman who presented initially after a year of secondary infertility with prolonged menstrual flow. Her last pregnancy ended in a suction dilation and curettage at 8 weeks' gestation for a missed abortion. A hysterosalpingogram revealed a solid 5 x 4.5 cm filling defect impinging on the endometrial cavity suggestive of a submucosal leiomyoma. A vaginal sonogram confirmed the findings. The patient underwent a laparotomy for excision of the 5-cm friable, necrotic mass that was performed by curetting. Pathologic examination of the specimen revealed sheets of intermediate trophoblastic cells characterized by large polyhedral cells and positive human placental lactogen staining consistent with PSTT. The patient eventually underwent total abdominal hysterectomy 4 weeks later with no evidence of residual tumor on histologic examination.