RESUMEN
The labeling index (LI), representing the percentage of S-phase cells, was measured in the healthy colorectal mucosa of subjects without a personal or familial history of neoplasm as well as in persons with a positive history, and was compared to the LI in benign or malignant lesions in a total of 128 subjects. In the healthy mucosa, LI was lowest in control subjects; it rose progressively in patients with a personal history of adenoma, patients with non colorectal cancer, and colorectal cancer patients respectively. There was a significant increase in LI from healthy mucosa to adenoma to carcinoma. The pattern of labeling in the crypts was studied in 56 subjects with different familial and personal histories. Limitation of labeling to the deepest part of the crypts was observed in control subjects and to a lesser extent in the healthy mucosa of patients with adenoma. An upward shift of the proliferative zone was observed in patients with a personal or familial history of cancer; adenomatous lesions had an inverse labeling distribution: labeling decreased from the luminal aspect towards the deep segments. High LI values and a shift of the proliferative zone towards the surface of the crypt may identify individuals at high risk for cancer of the colon and rectum.