Not Infrequent K-ras Mutations in Depressed-type Early Colorectal Carcinomas Larger than 10 mm

The aim of this study was to elucidate whether K- ras (codons 12 and 13) mutations occur in depressed-type early colorectal carcinomas (DECas) larger than 10 mm in size. Thirty-four cases of DECas including 27 larger than 10 mm were examined for K- ras mutations by means of microdis-section, PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism), and direct sequencing. Although K- ras mutation was infrequent (1/7, 14%) in small (less than 10 mm) DECas, 16/27 (59%) and 17/27 (63%) of DECas larger than 10 mm revealed codon 12, or either codon 12 or 13 mutations, respectively. None of the evaluated pathological factors except size showed a correlation with K- ras mutation. These data indicate that although K- ras mutation could not be involved in the early stage of the progression of DECas, it might play a role at a later stage when the tumor size is over 10 mm.