Renal cell carcinoma in children with diffuse cystic hyperplasia of the kidneys.

We report the clinical, pathologic, and genetic features of renal malignancy in two children with diffuse cystic hyperplasia. Both presented with massive bilateral nephromegaly. Neither had a family history or clinical findings suggestive of tuberous sclerosis or von Hippel-Lindau disease. The kidneys of both children were extensively replaced by tubulocystic hyperplasia with large eosinophilic epithelial cells. The masses of hyperplastic tissue were nodular, compressing remnants of uninvolved renal parenchyma. Tubulopapillary carcinoma was present in both children, one of whom had bilateral multicentric carcinoma. No loss of heterozygosity was detected in the tumors at the TSC1, TSC2, or VHL gene regions, and no alterations in the VHL gene were detected using single-strand conformation polymorphism analysis. These cases of bilateral renal enlargement with diffuse cystic hyperplasia appear to represent a new clinical syndrome that may warrant bilateral nephrectomy because of the risk of malignancy.