Proliferative patterns of rectal mucosa as predictors of advanced colonic neoplasms in routinely processed rectal biopsies

OBJECTIVES: We sought to determine whether the evaluation of rectal cell proliferation in routinely processed rectal biopsies of apparently normal mucosa can predict the presence of advanced colonic neoplasms. METHODS: Fifty consecutive patients, who did not meet any of the following exclusion criteria, underwent total colonoscopy. Patients with nonadvanced adenomas, inflammatory bowel disease, hereditary predisposition to colonic cancer, or a history of colonic neoplasms were excluded. Patients with neoplasms in the distal 40 cm of the large bowel were also excluded. An adenoma was considered advanced if it had a diameter > 1 cm, or villous or severe dysplasia histology were present. In 26 of the 50 patients (Group A: 16 men, 10 women; mean age, 65 yr) advanced colonic neoplasms (advanced adenomas or cancer) were detected; in the remaining 24 (Group B: 13 men, 11 women; mean age, 66 yr) the large bowel was free of neoplasms. In all patients the proliferative patterns of apparently normal rectal mucosa were evaluated using the monoclonal antibody MIB-1 to assess the expression of Ki-67 antigen in routinely processed tissues. Proliferation index for the entire crypt, as well as proliferation indices for each of the five equal compartments, into which the crypt had been divided longitudinally, were calculated for each patient. RESULTS: The mean proliferation indices were similar between the two groups compared. The mean proliferation index for the upper crypt compartments (4 + 5) in the Group A patients was significantly higher than for those of the Group B patients (p < 0.01). Multivariate stepwise logistic regression analysis revealed that among gender, age, and proliferative parameters, the pattern of cell proliferation in the upper rectal crypt (4 + 5) compartment was the only predictor of advanced colonic neoplasms (beta = 11.01, p < 0.001). CONCLUSIONS: Our data suggest that the evaluation of the upward expansion of the rectal crypt proliferative zone in routinely processed rectal biopsies of apparently normal mucosa appears to predict the presence of advanced colonic neoplasms. These preliminary results should be confirmed in larger studies.