title: Infrequent K-ras activation in superficial-type (flat) colorectal adenomas and adenocarcinomas.
abstract: Clinicopathological evidence is accumulating that a superficial-type (flat) colorectal tumor is a distinct neoplastic entity. To clarify the genetic characteristics of this tumor, we investigated the K-ras gene mutations and morphological features of 43 tumors of this type. A mutation of the K-ras codon 12 was detected in only 5 (16%) of 31 adenomas and 2 (17%) of 12 adenocarcinomas. The presence or absence of this mutation was not correlated with the tumor size or stage or with histopathological findings. None of these tumors had a mutation in codon 13 or exon 2, including codon 61. This low incidence of K-ras mutations (16%) suggests that superficial-type colorectal tumors are etiologically distinct from ordinary colorectal polypoid tumors and that there may be an alternative pathway of colorectal tumorigenesis.
authors.affiliation: Biochemistry Division, National Cancer Center Research Institute, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Minamoto
authors.forename: K
authors.initials: K
authors.lastname: Sawaguchi
authors.forename: M
authors.initials: M
authors.lastname: Mai
authors.forename: N
authors.initials: N
authors.lastname: Yamashita
authors.forename: T
authors.initials: T
authors.lastname: Sugimura
authors.forename: H
authors.initials: H
authors.lastname: Esumi
mesh_terms: D000230:Adenocarcinoma / Q000235:genetics* / Q000473:pathology; D000236:Adenoma / Q000235:genetics* / Q000473:pathology; D000328:Adult; D000368:Aged; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D017354:Point Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction