Pedunculated malignant colonic polyps with superficial invasion of the stalks.

Malignant colonic polyps on substantial stalks were seen in 3 patients. In each case the base of the pedicle was free of tumor. The author suggests that these were initially benign adenomatous polyps but subsequently became malignant. These findings suggest that initially benign colonic polyps can become malignant over a period of time and that the presence of a substantial stalk may not always be pathognomonic of benignity.