INITIATING GENETIC EVENTS IN SMALL RENAL NEOPLASMS DETECTED BY COMPARATIVE GENOMIC HYBRIDIZATION

Purpose: To identify the genetic alterations associated with renal ade nomas. Materials and Methods: We analyzed 37 renal adenomas obtained a t autopsy (23 papillary and 14 non-papillary) by comparative genomic h ybridization. Results: In papillary tumors, the median number of gains and losses of genetic material per tumor was 2.0 and 1.0, respectivel y. Papillary tumors were characterized predominantly by gains of genet ic material on chromosomes 7 (57%), 17 (35%), 16 (26%), 12 (26%), 3 (2 2%), 20 (22%) and loss of a sex chromosome (83%). In 6 papillary tumor s less than or equal to 5 mm. in diameter, gain of chromosome 7 occurr ed in 4 specimens. Initiating events for papillary renal adenomas incl ude gain of chromosome 7 and loss of a sex chromosome. In non-papillar y tumors, the median number of gains and losses of genetic material pe r tumor was 1.0 and 1.0, respectively. Nonpapillary tumors were charac terized by loss of genetic material on chromosome 3p (50%), loss of a sex chromosome (36%) and a gain of chromosome 5 (43%). The initiating event for non-papillary renal adenomas is the loss of chromosome 3p. C onclusions: Renal adenomas demonstrate similar genetic alterations as clinically detected renal, cell carcinomas. Their clinically indolent course may, in part, be a result of the lower number of genetic altera tions per tumor than their clinically detected counterparts. Renal ade nomas are thus small carcinomas which have not yet acquired the necess ary genetic alterations leading to tumor progression.