Wang, male, 16 days, 252249, 63597855, left renal tumor. Tumor resection was performed, P16-265: congenital mesangial nephroma of the left kidney (classic). Tumor cells were seen under the epithelium of the renal pelvis. No tumor cells were seen at the cut end of ureteral vessels and ureteral tissue. The tumor was 5.5*3.5*3cm with intact envelope. Grayish-yellow nodules were seen in the cut surface, 4*3*3cm, with nodules close to the renal pelvis and tough texture. Low grade malignant tumor, close postoperative follow-up is recommended, there is 20% recurrence possibility, regular review and surgical follow-up.