Polyps of the rectum and colon.

Four hundred and thirty-three patients with adenomatous polyps were examined and followed up. It was found that well differentiated adenomas are stable but dedifferentiated polyps can lead to invasive cancer, usually over a long period of time. Thus the concept of malignant transformation becomes meaningless, and should be replaced by an initial histological evaluation of polyps of the rectum and colon so that their development can be predicted.