K-RAS MUTATION IN A TUBULAR ADENOMA ORIGINATING AT AN ILEOSTOMY IN A FAMILIAL ADENOMATOUS POLYPOSIS PATIENT

Genetic alterations in a tubular adenoma with severe dysplasia arising in a Brooke ileostomy of a familial adenomatous polyposis patient wer e analyzed. Clinical and morphological characteristics suggest that il eal mucosa progressed to colonic metaplasia and then to dysplastic ade noma, Such changes at ileostomy sites are rare, and little is known ab out the associated genetic alterations, To determine whether metaplast ic epithelium progression to adenoma in the ileum is subject to the sa me mutations identified in colon carcinogenesis, we evaluated somatic genetic alterations associated with sporadic colorectal cancer develop ment, Sequences examined included mutation cluster regions of the p53 tumor suppressor gene and the K-ras oncogene, Using polymerase chain r eaction and DNA sequencing, we identified a point mutation at codon 12 of the K-ras oncogene, To our knowledge, this is the first report of a ras mutation occurring in a tumor originating from ileal mucosa.