Lack of evidence of Ki-ras codon 12 mutations in melanocytic lesions.

A number of studies have failed to detect point mutations at codon 12 in the Ki-ras gene in melanocytic neoplasms. One recent study, however, has found a high percentage of Ki-ras codon 12 point mutations. In an effort to resolve this difference, the present study examined noncultured melanocytic lesions (i.e., 5 benign nevi, 10 dysplastic nevi, and 8 primary melanomas: 4 in situ and 4 invasive) for point mutations at codon 12 in the first exon of the Ki-ras proto-oncogene using polymerase chain reaction methodology with oligonucleotide hybridization and direct DNA sequencing. The results of this study indicates no detectable mutations in the 12th codon of the first exon of the Ki-ras gene in any premalignant or malignant melanocytic lesion examined.