Precursors of human colon carcinoma: a serial section study of colectomy specimens.

All polyps and strips of colonic mucosa 1 to 15 cm from tumor margins were examined for possible precursors of carcinoma in 24 patients undergoing partial colectomy for primary colorectal adenocarcinoma. Of 114 polyps found, 40.4% were adenomatous, and the remainder were hyperplastic or inflammatory or showed normal mucosa. No primarily dysplastic lesions, which could be interpreted as early de novo carcinomas, were found. Serial sections of mucosal strips revealed minute adenomatous foci in 3 of 24 patients, one of whom also showed several patches of exclusively dysplastic epithelium. This finding suggest that carcinoma may rarely arise de novo, but most carcinomas appear to be accompanied by (? preceded by) adenomatous changes.