Genetic subtyping of renal cell carcinoma by comparative genomic hybridization

The prognosis of renal cell carcinoma (RCC) varies dependent on histologic tumor subtypes. However, differentiation between RCC types may sometimes be difficult on histologic grounds alone. Furthermore, the prognostic value of histologic parameters for the individual prognosis is limited. Additional information on the molecular level seems necessary to obtain more certainty in diagnostic and prognostic evaluation. By investigating genetic alterations in different RCC subtypes, we sought to obtain a genotype-phenotype correlation. Eighty-two clear-cell, 53 papillary, 23 chromophobe RCCs and 26 renal oncocytomas were investigated. Comparative genomic hybridization (CGH) was performed on DNA from paraffin-embedded tissue samples. DNA was isolated from tumor areas by microdissection and amplified by degenerated oligonucleotide primed polymerase chain reaction (DOP-PCR). CGH was performed according to standard protocols. We were able to detect specific alterations in each RCC subtype: clear cell RCC showed -3p, +5/5q, -8p, -9, -14, -18; papillary (chromophilic) RCC gains of chromosomes 7, 17, 16, 3, 12; chromophobe RCC loss of chromosomes 1, 2, 6, 10, 13, 17, 21; renal oncocytomas loss of chromosomes 1/1p and 14. Furthermore, for clear cell RCC, it was possible to define alterations which are associated with metastatic disease: loss of 9, 10, 14. Our results demonstrate that each RCC subtype is characterized by distinct genetic alterations. The definition of genetic alterations seems helpful for a tumor typing especially when morphology is equivocal. Therefore, genetic analyses represent a powerful diagnostic and prognostic tool for RCC.