CT and MRI findings in a case of pelvic schwannoma.

We compared the diagnostic utility of computed tomography (CT) and magnetic resonance imaging (MRI) in a patient with a pelvic schwannoma. This 46-year-old woman was admitted for evaluation of a retroperitoneal pelvic mass and myoma uteri. The retroperitoneal pelvic mass had been detected by a CT scan at a routine health examination. A CT scan revealed a well-circumscribed cystic tumor (4 x 3 cm) at the right internal obturator muscle portion. The CT number of the inner part of the tumor was 21. Only the cyst wall was enhanced by injection of a contrast medium. MRI showed a 4 x 3 x 3-cm retroperitoneal cystic tumor that demonstrated low-intensity signals on T1-weighted images and high-intensity signals on T2-weighted images. Small areas of low intensity inside the tumor were observed on T2-weighted images. Histological examination revealed a typical schwannoma of mixed Antoni type A and type B. These findings indicate that both MRI and CT are useful for diagnosis of retroperitoneal schwannomas.