The patient was a 24-year-old man who had a left renal mass noted incidentally during a medical examination at the People's Hospital of China Three Gorges University (Yichang, China) in March 2016. Ultrasonography performed on the patient showed a left kidney mass (9.4 × 5.9 cm) located in the site of left renal pelvis with blood signs. Nevertheless, he had no history of headache, sweating, hypertension, or lumbar pain, and laboratory examinations included routine blood urinary, function of liver and kidney, and serum catecholamine indicated no abnormality. He was admitted.A plain computed tomography (CT) scan of the patient's upper abdomen demonstrated a heterogeneous mass (7.6 × 5.9 cm) in the left renal area involving the pelvicalyceal system (Fig. 1A). Contrast-enhanced CT results showed an increasing heterogeneous density of the mass, which compressed the left renal parenchyma with distinct border after injection of iodine-containing solution (Fig. 1B). Moreover, CT angiography indicated that the rates of both renal glomerular filtration and renal blood reperfusion were normal.Based on these tests, the patient was diagnosed with a left renal pelvic tumor provisionally and underwent left radical nephrectomy by transperitoneal laparotomy. At operation, the mass was at the middle and lower pole of the left kidney, involving the renal pelvis. Renal artery was then interim blocked and radical excision of the left kidney was done owing to the tumor being almost in the renal parenchyma. Notably, the cut section showed a chocolate brown part measuring 9 × 5 × 4.5 cm in the renal pelvis and another brown