MR imaging of pelvic extraperitoneal masses: A diagnostic approach.

Pelvic extraperitoneal pelvic masses are relatively uncommon conditions and generally raise diagnostic imaging challenges. Magnetic resonance (MR) imaging plays a central role in the diagnosis of these masses due to its unique tissue-specific multiplanar capabilities that allow optimal pelvic mass localization and internal characterization. This article reviews the MR imaging presentation of extraperitoneal pelvic masses, gives clues that allow identifying their extraperitoneal and/or specific origin as well as suggests different steps for narrowing the differential diagnosis. These steps include systematic analysis of the clinical context, tumor location, relationships with major pelvic structures and close study of the internal components of the lesions.