Rectal mucosa. Malignant and premalignant changes after radiation therapy.

A spectrum of changes that range from crypt basophilia through varying degrees of dysplasia and carcinoma in situ have been observed in the flat, nonraised mucosa of the rectum in patient who received pelvic irradiation for carcinoma of the cervix. This case demonstrates (1) the morphological evidence of the relationship between radiation and large-bowel carcinoma, (2) that large-bowel carcinoma may arise directly from the flat mucosa without having to go through a benign polyp-cancer sequence, (3) that early carcinoma arising from the flat mucosa may clinically resemble radiation proctocolitis, and therefore, (4) that increased vigilance in needed for the follow-up of patients who undergo pelvic irradiation.