Case 2. Cystic cellular mesoblastic nephroma.

Mesoblastic nephroma is a benign mesenchymal tumor of the kidney generally diagnosed during the first 3 months of life. A case of the cellular variant of mesoblastic nephroma associated with prominent cystic change and renal vein invasion arising in an 8-month-old female is described. This unusual case expands the morphologic spectrum of mesoblastic nephroma.