Botryoid Wilms tumor: case report and review of literature.

A rare case of botryoid Wilms tumor is presented. The main clinical manifestations were persistent low-grade fever, malaise, and proteinuria associated with microhematuria. Ultrasonography revealed an echogenic mass in the right kidney, and a contrast-enhanced mass was found in the dilated collecting system by contrast-enhanced computed tomography. The surgically resected tumor was a polypoid, light-yellow, glistening mass that occupied a large part of the renal pelvis and originated from the pelvicaliceal wall. Part of the tumor extended to the proximal ureter, resulting in hydronephrosis in the involved kidney. No parenchymal lesion was observed. Microscopic examination revealed epithelial, stromal, and blastemal components, which indicated Wilms tumor. Infection had occurred in the hydronephrotic kidney, which presumably had caused the major presenting symptoms. The prognosis of our patient and previously reported cases of botryoid Wilms tumor was good compared with that of typical Wilms tumor, since the botryoid type can be detected at an early stage.