Gallbladder adenomas have molecular abnormalities different from those present in gallbladder carcinomas

Although most gallbladder carcinomas evolve from dysplasia and carcinoma in situ, the role of gallbladder adenomas in the pathogenesis of gallbladder carcinoma is still controversial. A series of molecular changes including l oss of heterozygosity (LOH) at 17p (TP53 gene), 13q (RB gene), 18q (DCC gen e), and 9p21 (CDKN2a gene) chromosomal regions have been identified in dysp lasias, carcinomas in situ, and invasive carcinomas of the gallbladder, whe reas mutations in K- and N-ras genes are rare. To determine whether the mol ecular abnormalities of adenomas are similar to those found in carcinomas, we obtained extracted DNA from precisely microdissected tissue from 16 gall bladder adenomas (14 pyloric and 2 intestinal-type). We determined the pres ence of mutations in TP53, K- and N-ras genes, and LOH at five chromosomal regions (5q22 APC-MCC region, RE, TP53, DCC and 9p21-CDKN2 alpha). For the TP53 mutation study, single strand conformational polymorphism (SSCP) analy sis in exons 4 to 8 were performed. K- and N-ras mutations detection was pe rformed by designed restriction fragment length polymorphism (RFLP) method and sequencing. Only a single LOH (at 5q22) was detected in a gallbladder a denoma of intestinal type. No mutations at the TP53 were detected. Four ade nomas (25%) showed K-ras mutations (two in codon 12 and two in codon 61). W e conclude that gallbladder adenoma lacks the molecular changes frequently detected in dysplasia, carcinoma in situ, and invasive carcinoma of the gal lbladder. Likewise the occurrence of K-ras mutations at codon 12 and 61 in 25% of adenomas strongly suggests that these lesions are not precursors of invasive gallbladder carcinoma. HUM PATHOL 30:21-25. Copyright (C) 1999 by W.B. Saunders Company.