Analysis of K-ras gene mutations in periampullary cancers, gallbladder cancers and cholangiocarcinomas from paraffin-embedded tissue sections.

Point mutations of the K-ras gene were analyzed in 25 periampullary cancers (21 ampulla vater cancers, two common bile duct cancers and two duodenal cancers), two gallbladder cancers and six cholangiocarcinomas. DNA extracted from the paraffin-embedded tissues was amplified with the polymerase chain reaction and subsequently analyzed by direct cycle sequencing at codons 12, 13 and 18 of the K-ras gene. Codon 61 was first screened with single strand conformation polymorphism and then sequenced by direct cycle sequencing. No point mutation was found in any of the 25 periampullary cancers or the two gallbladder cancers. These results are similar to previous reports. Mutation of the K-ras gene seems not to play an important role in tumorigenesis of periampullary cancer. In two of six (33%) cholangiocarcinoma patients, point mutations were found. Both mutations were transitions, GGT to GAT at codon 12. The incidence of mutation was greater than that in Thailand (about 8%) but less than that in Japan (about 60%). Mutation of the K-ras gene may play varied roles in the tumorigenesis of cholangiocarcinoma, depending on geographic area.