Different ras gene mutational frequencies in thyroid papillary carcinomas in Japan and Thailand.

The incidence and pattern of ras oncogene mutations in human malignancies demonstrate geographic and racial differences. For example, specificity of alterations is found in cholangiocellular carcinomas in Thai patients with a different etiology from those in Japanese patients. In the present study, a comparison of ras gene mutations in thyroid papillary carcinomas from Japanese and Thai patients was performed using single-strand conformation polymorphism and direct sequencing analyses. The incidence of ras mutation differed markedly in Japanese (two of 24 carcinomas, 8.3%) and Thai (five of 10 carcinomas, 50%) patients. In addition, all but one ras mutation occurred at codon 12 of the K-ras gene in the Thai cases. These results suggest that thyroid cancers in Thailand may be due to specific genetic and/or environmental factors.