Sonographic detection of fibromatosis: a rare tumor in the retroperitoneum.

Abdominal sonography for the detection and evaluation of mass lesions is a common investigative modality. The authors wish to report a case of an unusual retroperitoneal tumor that was detected by ultrasound. The lesion, fibromatosis, was symptomatic but went undiagnosed for over a year, despite two evaluations which included multiple standard roentgenographic studies. Fibromatosis is discussed.