Remnants of adenomas in colorectal carcinomas.

In consecutive large bowel resectates in patients older than age 20 years, primary colorectal cancer remnants of adenomas were histologically identified in 39 of 169 carcinomas (23%). Remnants of pure tubular adenomas were seen in 17 and of tubulovillous adenomas in 22 cases. There was no significant difference among sexes, intestinal segments, or age groups older than 55 years with the regard to the frequency of adenomas in carcinomas. A very low are (0.05) was found in patients of both sexes younger than 55 years. The frequency with which adenomas was identified was independent of tumor size. A high rate was found in those carcinomas which were limited to the submucosal layer (0.57), were well differentiated (0.43), and had an exophytic growth (0.54). Coexisting single or multiple adenomas at a distance from the main tumor were significantly more frequent in resectates in which adenomas was detected in the carcinoma (0.51) than in resectates in which no adenoma contiguous with the carcinoma was seen (0.30). The study shows that carcinomas develop from adenomas in all parts of the large intestine, but it cannot be concluded that all carcinomas in noncolitic patients develop from adenomas.