Abstract: In a 26-week repeated dose toxicity study with SD rats,one case of nephroblastoma is observed in the vehicle control group (0.9% saline) after the administration.The gross morphology shows that the right abdomen inflated and the whole right kidney is a mass.Some areas of the mass is gray or black brown.The mass is larger,irregular shape,pseudocystic fibrosis can be seen on the surface of the mass.The texture of the mass is both hard and soft.Left kidney is normal.HE staining shows that large mass involved most of the kidney and are surrounded by a pseudocapsule of compressed renal parenchyma.The mass in the rat is characterized by a triphasic pattern of blastemal,epithelial and stromal cells.Organoid epithelial differentiation into glomeruloid and epithelial-lined tubules further characterizes nephroblastoma.The above results are in line with the diagnostic features of nephroblastoma.

Key words: SD Rats, Nephroblastoma, Pathomorphology