Retroperitoneal schwannoma misdiagnosed as an ovarian malignancy

A 55-year-old woman presented to the hospital with abdominal discomfort over 3 months. Contrast-enhanced abdominal CT showed a 10×9×6.5 cm sized well-defined solid-cystic enhancing mass in the right pelvic cavity. Under general anaesthesia, exploratory laparotomy was performed on suspicion of ovarian malignancy. Pathological examination revealed a retroperitoneal schwannoma with highly ordered cellular component (Antoni A) and hypocellularity with predominantly loose myxoid component (Antoni B). On immunohistochemical staining, the sample showed typically positive result for S-100 in the cytoplasm of the tumour cells. Schwannomas are consisting only of Schwann cells and are most often non-malignant tumors. It is relatively slow growing and usually located in the head, neck and the extremities. Schwannomas are quite rare in the retroperitoneal region. The diagnosis of retroperitoneal schwannomas is often delayed and misdiagnosed as an adnexal tumour, especially locating in the pelvic cavity. Surgical complete resection of tumour is the treatment of choice and recurrence is unusual after complete resection.