Synchronous primary adenocarcinomas of the colon and rectum.

In a series of 1,002 cases of primary colorectal adenocarcinomas diagnosed during a ten-year period there were 62 (6.2%) patients who had two or more primary colorectal adenocarcinomas. Most of the tumors were more than 5 cm away from each other: 27 carcinomas were separated by 6-10 cm, 16 were separated by 11-20 cm, and 12 were separated by more than 20 cm. It is concluded that the incidence of synchronous carcinomas of the colon is sufficiently high to warrant a search by both surgeon and endoscopist for additional tumors some distance from the initial lesion.