The genetics of renal oncocytosis: a possible model for neoplastic progression.

Renal oncocytosis is a rare condition characterized by the presence of numerous oncocytomas and oncocytic changes in the renal tubules. Other than oncocytomas associated with the Birt-Hogg-Dube (BDH) syndrome, the genetics of oncocytosis is not known. Whether oncocytomas and oncocytosis are similar to BDH syndrome, in which the tumors diploid (as most oncocytomas are), or show chromosomal losses may be significant regarding the observation that in oncocytosis, there frequently is morphological evidence of progression to chromophobe carcinoma. Here we report on the case of a 69-year old male who underwent a staged procedure of partial nephrectomy on the left side and right radical nephrectomy for multiple renal tumors. The tumors were studied by routine hematoxylin and eosin morphology, immunohistochemistry, cytogenetics, and loss of heterozygosity analysis. Both kidneys had numerous oncocytic neoplasms morphologically progressing from oncocytomas to hybrid tumors with chromophobe carcinoma. Genetic studies demonstrated progression from normal cytogenetics to chromosomal losses similar to those in some oncocytomas and in chromophobe carcinomas. The genetics of this apparently nonfamilial oncocytoma differs from that of BDH syndrome and is characterized by losses involving chromosomes 1, 14, 21, and Y. To our knowledge, this is the first report of the genetic and cytogenetic findings in oncocytosis not related to BDH syndrome and may suggest a possible model of progression from oncocytoma to chromophobe renal cell carcinoma.