Renal tumors are represented by:
mesoblastic nephroma (renal hamartoma) and
Wilm’s tumor (nephroblastoma).
Mesoblastic nephroma is the most frequent renal tumor, while Wilm’s tumor is extremely rare. The sonographic picture in both tumors is of a solitary mass replacing the normal architecture of the kidney, in most cases with associated polyhydramnios. Cystic areas may appear in both tumors. Mesoblastic nephromas are benign, and nephrectomy is curative in the majority of cases.