Cystic nephroma: morphologic spectrum and implications.

Among 216 primary renal tumors collected from a pediatric population in metropolitan Chicago, 6 instances corresponded in multiloculated cystic masses conforming to the diagnostic criteria of so-called cystic nephroma. Histopathologically, the component tissues were entirely mature in 2 cases, but in the remaining 4 the septa between cysts contained variable amounts of primitive or embryonic tissues; in one of these, a grossly visible mass formed a nodule of typical Wilms tumor. Our experience agrees with previous reports that favor closer structural similarity of these lesions to nephroblastoma than to any known form of cystic malformation. This concept has important consequences on the therapeutic approach to preoperatively diagnosed multilocular cystic masses of the kidney, and supports the idea that nephrectomy is the treatment of choice. Metastases or local recurrence have not been reported in cases of cystic nephroma.