A 57-year-old woman with non–insulin-dependent diabetes mellitus and no other medical history had worsening left-sided back pain over 4 months and no other symptoms. Physical examination findings were significant for mild left flank pain, but there was no costovertebral angle tenderness. Laboratory results were within normal limits. Axial imaging demonstrated an exophytic, retroperitoneal mass with solid and cystic components involving the left kidney, posterior abdominal wall, and mesocolon (Figure 1). The mass measured 20 cm in its greatest dimension. Findings on colonoscopy and mammography were negative. Positron emission tomography–computed tomography did not reveal any other abnormality.
Leon Guerrero A, Hatzaras I. Retroperitoneal Mass. JAMA Surg. 2015;150(2):175-176. doi:10.1001/jamasurg.2014.364