Renal oncocytoma in a kidney transplant patient: the imaging features on contrast-enhanced ultrasonography (CEUS): a case report.

Renal oncocytoma is an infrequently reported renal neoplasm, often asymptomatic, which usually behaves as a benign entity and is identified accidentally on radiological imaging. Transplant patients under long-term immunosuppressive drugs have a high prevalence of cancers, such as skin cancers, lymphoproliferative disorders, and renal carcinomas. We present a case report of an asymptomatic renal oncocytoma in a kidney transplant recipient presenting persistent hematuria. The features of computed tomography and contrast-enhanced ultrasound (CEUS) are presented. This was the first time we used CEUS in a transplant kidney recipient presenting a renal mass, allowing the real-time visualization of contrast-enhancement patterns during all vascular phases for the differential diagnosis of renal tumors. Although the pattern of intense vascularization could mislead to an early judgment as a malignant lesion, it could help to exclude other renal lesions without inducing nephrotoxicity.