Abstract

Typical nephroblastoma arise within the renal parenchyme and have pseudocapsules composed of compressed renal tissue, renal capsule and adjacent perirenal tissue. Therefore, it is rarely possible to determine whether the tumor arose from the cortex or medulla. Many authors believe that they are probably cortical in origin and arise from nodular renal blastema just beneath the renal capsule or in the centers of columns of Bertin. We experienced a nephroblastoma supposed to arise from peripelvic region. The patient was a 7 months old male infant with an abdominal mass. Left nephrectomy was done under the impression of nephroblastoma. Received specimen was a diffusely enlarged kidney with preserved normal outline, so it looked like a hydronephrotic kidney. On section, the pelvis and calyceal system were dilated and totally filled with a gray white soft mass. Most portion of the mass was floating freely in the calyces and pelvis, and only a small portion was attached to the renal parenchyme but without invasion to it. Microscopically the mass was a nephroblastoma containing many well developed glomeruli and tubules. We presumed that the tumor arose from a nodular renal blastema in the peripelvic region, because the tumor had no connection to the renal cortex.