Renal Collision and Composite Tumors: Imaging and Pathophysiology

ObjectiveTo illustrate the imaging appearances of a spectrum of renal collision and composite tumors. Occurrence of collision and composite tumors in the genitourinary tract is rare compared to the usual occurrence of synchronous tumors.MethodsCase studies were chosen that represent the different tumors. Analysis was made on both the imaging and the pathology if excision was performed.ResultsPresence of 2 different cell types can lead to confusing imaging findings, and biopsy or excision is typically needed for final diagnosis. Some composite tumors have a characteristic appearance on imaging based on their pathologic features.ConclusionFamiliarity with imaging findings may help radiologists include these tumors in their differential diagnosis.