MR imaging of common and uncommon large pelvic masses.

Magnetic resonance (MR) imaging is often used in the detection and staging of large pelvic masses. Many large masses in the female pelvis arise from the reproductive organs (eg, uterus, cervix, ovaries, fallopian tubes). In addition, these masses may arise from the gastrointestinal system, urinary system, adjacent soft tissues, peritoneum, or retroperitoneum or from metastases. The majority of large masses in the female pelvis represent such commonly encountered entities as uterine fibroid tumor, dermoid tumor, ovarian cyst, and ovarian cancer. However, uncommon pelvic masses such as mesothelioma, adenocarcinoma, carcinosarcoma, leiomyosarcoma, and desmoid tumor may also be seen. Thus, the differential diagnosis for female pelvic masses is extensive. However, the site of origin, MR imaging characteristics, and clinical history may all help narrow the differential diagnosis. Although with large tumors it may not always be possible to determine the site of origin or distinguish between various tumors at radiology, familiarity with the clinicopathologic and MR imaging features of common and uncommon pelvic masses is important for diagnosis and treatment.