Sacral Nerve Sheath Tumor Simulates a Pedunculated Fibroid on Sonography

Abstract

Received February 23, 2007, from the Department of Radiology, University of California Davis Medical Center, Sacramento, California USA. Revision requested March 29, 2007. Revised manuscript accepted for publication May 10, 2007. We thank Tammy LaPolt and Julie Ostoich for manuscript and image preparation. Address correspondence to Maria Luisa C. Fogata, MD, Department of Radiology, University of California Davis Medical Center, Suite 3100, 4860 Y St, Sacramento, CA 95817 USA. E-mail: maria.fogata@ucdmc.ucdavis.edu Abbreviations MRI, magnetic resonance imaging; PNST, peripheral nerve sheath tumor 28-year-old female patient with a history of menorrhagia and intermittent leg pain was referred for pelvic sonography. Transabdominal and endovaginal pelvic sonography was performed. Gray scale sonography showed a complex left adnexal mass isoechoic to the uterine myometrium (Figure 1). The uterus and both ovaries appeared normal in size and morphologic characteristics. The left adnexal mass measured 4.2 × 3.5 × 3.5 cm, had a cystic component, and was seen separate from the ovary. Color Doppler sonography showed some vascularity to the mass. A pedunculated fibroid was considered because the mass appeared isoechoic to the myometrium, although connection of the mass with the uterus was not seen. A neurogenic tumor was considered in the differential diagnosis due to symptoms of leg pain. Other differential possibilities included endometrioma, a hemorrhagic cyst, an ovarian tumor such as a fibroma or Brenner tumor, and pelvic inflammatory disease. Magnetic resonance imaging (MRI) was suggested for further evaluation and showed a left pelvic mass that was contiguous with a nerve root in the sacral foramina, consistent with a sacral peripheral nerve sheath tumor (PNST) (Figure 2). The mass showed heterogeneous low signal intensity on T1-weighted images and heterogeneous high signal intensity on T2-weighted images. Postcontrast images showed peripheral enhancement in the mass. The left pelvic side wall mass was resected, and pathologic diagnosis showed a PNST (schwannoma). This unique case shows the importance of including gynecologic and nongynecologic causes in the differential diagnosis of an unusual pelvic mass. Nongynecologic pelvic masses such as neurogenic, gastrointestinal, and extraperitoneal masses, including a presacral teratoma or