Schwannomas, also known as neurilemmomas, are rare tumors that arise from the peripheral nerve sheath. We present a young woman with a presacral schwannoma mimicking a pedunculated leiomyoma and producing sciatic pain. Gynecological examination revealed a hard, palpable, tender mass in the right adnexal region. Transvaginal ultrasound revealed a homogenous tumor mass measuring 4 x 5 cm next to the right ovary but not attached to it. Color Doppler ultrasound showed the vascularity of the tumor to match closely the vascularity of the uterine muscle. The suspected diagnosis was subserous uterine leiomyoma. The patient underwent surgery 4 weeks later. An encapsulated yellowish-white tumor was tightly attached to the sacrum, and to prevent rupture of the tumor, the laparoscopic procedure was converted into laparotomy. The histopathological diagnosis was a benign soft tissue tumor, a schwannoma. The patient’s recovery was uneventful. She has now been asymptomatic for 9 months, and her lower back pain has disappeared. The present case demonstrates the difficulty to discriminate between a presacral schwannoma and a pedunculated leiomyoma.

Keywords: Schwannoma, Presacral tumor, Retroperitoneal tumor