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.