Insertion (8;11) in a renal oncocytoma with multifocal transformation to chromophobe renal cell carcinoma

We report the case of a 43-year-old male with multiple tumor foci showing microscopic features of chromophobe renal carcinoma (ChRCC) arising in an oncocytoma. Conventional cytogenetics of fresh tumor cells and fluorescence in situ hybridization (FISH) revealed the following abnormal karyotype: 46,XY,der(8)ins(8;11)(p?;q13),der(11)ins(8;11)inv(11)(q12?p15) with CCND1 (11q13) rearrangement. To our knowledge, chromosome 8 has not been reported as a partner involved in structural rearrangements of 11q13 in oncocytomas. FISH in paraffin tissue sections revealed a rearrangement of CCND1 (11q13) in the oncocytoma cells. The multiple foci of chromophobe carcinoma presented multiple copies of CCND1, suggesting that they represented a transformation from oncocytoma into ChRCC. There was immunohistochemical overexpression of CCND1 in both oncocytoma and chromophobe carcinoma cells. In this case, the correlation of the microscopic findings with changes in CCND1 gene associated to CCND1 overexpression in both components suggest that the ChRCC would have originated from the preexisting oncocytoma. It is not possible to detect, by cytogenetic techniques alone, if the ChRCC component have also the CCND1 rearrangement in addition to the detected polysomy. FISH techniques on paraffin tissue sections may help to identify genetic aberrations such as CCND1 rearrangement in order to establish a diagnosis of oncocytoma.