CYTOGENETIC ANALYSIS OF INTESTINAL POLYPS IN POLYPOSIS SYNDROMES - COMPARISON WITH SPORADIC COLORECTAL ADENOMAS

Few cytogenetic studies of polyps from patients with polyposis syndrom es have been reported. We studied 27 colonic adenomatous polyps from f amilial adenomatous polyposis (FAP), two polyps of the small bowel fro m Peutz-Jeghers syndrome (PJS), and four colorectal juvenile polyps fr om juvenile polyposis syndrome (JPS). The karyotypic results were comp ared with 32 sporadic colorectal adenomatous polyps. Nineteen colorect al adenomas had abnormal karyotypes; of these, five were from patients with FAP and 14 were sporadic adenomas. Numerical changes were the mo st frequent change (14 adenomas); additional copies of chromosome 7 (e ight adenomas) and 13 (seven adenomas) occurred most often and were pr esent in both FAP and sporadic adenomas. Only five adenomas, all spora dic, had structural chromosome abnormalities. Normal karyotypes were o btained from 32 adenomas, and chromosome counts but not karyotypes wer e obtained from eight polyps owing to poor chromosome morphology. The JPS and PJS polyps had normal karyotypes. These data indicate that ade nomas from patients with FAP tend to have fewer structural abnormaliti es than sporadic adenomas and that numerical abnormalities are the mos t common chromosome abnormality in both FAP and sporadic polyps and su ggest that the mechanism which causes loss of heterozygosity (LOH) in the adenoma to carcinoma sequence operates on a level below that of th e whole chromosome.