Congenital cystic mesoblastic nephroma.

Congenital mesoblastic nephroma is a relatively rare infantile renal tumor. It comprises 3-6% of renal masses in childhood and 50% during the neonatal period. Most mesoblastic nephroma occur in the newborn period, with 80% of the cases being reported within the first month of life. Macroscopically the tumor is composed of a solid mass of different sizes tending to invade the surrounding structures and renal parenchyma. The authors report a case of cystic mesoblastic nephroma of the cellular subtype, with diffuse areas of hemorrhage and necrosis. The tumor was treated by surgical excision with radical nephrectomy and the child is doing well 4 years after the operation.