Surgery Clinical Challenge – A Rare Cause of Retroperitoneal Mass

A 52 year-old female with a past medical history of obesity and hypertension, presented to the surgical clinic after aretroperitoneal mass was found by computed tomography (CT). The patient reported right buttock pain and right-sided abdominal pain for six months prior to presentation. Physical exam revealed a non-tender abdomen without palpable masses or lymph adenopathy. Magnetic resonance imaging (MRI) of the pelvis with contrast revealed a smooth 8.5x9.5x5.7 cm mass in the right lower pelvis with subtle contrast enhancement (Figures 1 and 2). Enhancing solid components of the mass were inconsistent with a lipoma. The patient underwent an exploratory laparotomy that found a 12 cm retroperitoneal pelvic mass overlying the right iliacus muscle and extended into the right inguinal canal. The right ureter was identified early and prior to an en-bloc resection of the mass. The preliminary frozen section analysis of the mass was read as a lipoma. Permanent section did not corroborate the frozen section analysis.