Prevalence and distinctive biologic features of flat colorectal adenomas in a North American population

(Background & Aims) under bar: To assess the prevalence of fat and depresse d (F&D) colorectal adenomas in the United States, we performed a prospectiv e study of 211 American patients. (Methods) under bar: Dye-assisted colonos copy was performed in the presence of both an American and a Japanese inves tigator, (Results) under bar: F&D lesions were found in 22.7% of patients, and these were more likely to be adenomatous than polypoid lesions (82% vs, 67%; P = 0.03) and contained mote invasive cancer (4.5% vs, 0%; P = 0.04), which also appeared to be at a disproportionately advanced stage. The aver age size of all F&D advanced lesions (high-grade dysplasia and cancer) was significantly smaller than comparable polypoid lesions (10.75 +/- 2.7 mm vs . 20 +/- 2.9 mm; P < 0.05), F&D adenomas showed significantly stronger frag ile histidine triad (FHIT) expression and lower p53 reactivity than similar ly sized polypoid adenomas, whereas proliferative and apoptotic indices wer e similar in both groups, <(Conclusions)under bar>: We conclude that there is a significant prevalence of colonic F&D colorectal adenomas in this coun try and that these lesions have significantly different biologic features t han polypoid lesions. The clinical and epidemiologic implications of these findings for American patients need to be addressed in further studies.