Microscopic intraepithelial neoplasia in large bowel mucosa.

Early neoplastic changes within the nonpolypoid mucosa of the large bowel have been incidentally discovered in two individuals. One of these patients is a 31-year-old man without any known large bowel disease; the other is a 61-year-old woman with diverticulosis. Only small microscopic foci of several neoplastic crypts were observed in otherwise normal-appearing mucosa. This finding lends support to the concept that cells in the crypts, irrespective of their location either in the flat mucosa, polyps, diverticula, or elsewhere, are susceptible to neoplastic transformation.