Retroperitoneal oncocytoma: case report and review of the imaging features.

Oncocytomas are uncommon tumours that occur in a number of specific anatomical locations within the head, neck, chest, abdomen and pelvis. When occurring in the retroperitoneum, oncocytomas almost always arise from either the kidney or adrenal gland. With this case we present the imaging findings of an exceptionally rare retroperitoneal oncocytoma whose site of origin is neither the kidney nor adrenal gland.