Botryoid Wilms' tumor: report of two cases

Background: Botryoid Wilms' tumor is a rare kind of Wilms' tumor. We report two cases of this tumor. Methods: Case 1, a 2-year-old boy, was admitted with macrohematuria for 5 months. Case 2, a 19-month-old boy, was referred for a palpable abdominal mass. The two cases were checked by 64-row multi-slice spiral CT (MSCT) and scanned with the dynamic contrast enhancement. The masses were excised and pathologically confirmed. Results: In case 1, the mass occurred in the renal pelvis and calyx bilaterally, with heterogeneous density and prominent calcification. By contrast enhanced CT scan, the mass was mildly enhanced. In case 2, the left renal pelvis and ureter were filled with the tumor. Unenhanced scan revealed that the mass was homogeneous and non-calcified. In contrast, the mass was slightly and heterogeneously enhanced. Macroscopically, the mass filled in the pelvicalyceal system and had a botryoid appearance. Microscopically, the typical features of Wilms' tumor with blastemal, epithelial, and stromal components were evident. Conclusion: Botryoid Wilms' tumor should be included in the differential diagnosis of tumors in the pelvicalyceal system no matter it is unilateral or bilateral.