Differentiation of multifocal renal cell carcinoma by comparative genomic hybridization.

Multifocality occurs in 12-22% of all renal cell carcinoma (RCC) cases. In order to differentiate multifocal RCC, we performed comparative genomic hybridization (CGH) and correlated the results with histopathological and clinical data. After histopathological examination of multifocal tumors, tumor areas were dissected from histopathological sections. Isolated DNA was amplified by DOP-PCR. CGH was performed according to standard protocols. Twenty cases were analyzed. In eight cases, at least one identical aberration was detected in the related tumors. Another eight cases showed different chromosomal changes in tumors of the same kidney. In the small additional clear cell tumors typical genetic alterations of clear cell carcinomas were detected whereas in the chromophilic tumors aberrations characterizing both adenomas and carcinomas were found. From these results we conclude that multifocal RCC represents a heterogeneous group of tumors. The malignant potential of small additional tumors in multifocal RCC cannot be excluded.