Proliferative activity of normal and neoplastic colonic mucosa in population groups with high and low risk for colorectal carcinoma

Europeans have a high incidence of colorectal cancer in comparison to Afric ans. Lack of detectable sequence adenoma-colorectal carcinoma in Africans m ay suggest the development of adenocarcinoma is de novo. The aim of this st udy is to assess colonic mucosal proliferative activity in various patholog ical conditions of diverse population groups. Materials included routinely processed tissue specimens from consecutively resected well- and moderately differentiated colorectal adenocarcinomas from 32 rural Africans (South Af rica) and 27 urban Europeans (Poland) and from apparently normal rectal muc ous membrane from the age and sex marched each population group (28 and 25 samples respectively). In addition, 32 resected adenomatous polyps were exa mined in Europeans as well. The MIB 1 monoclonal antibody was used to assay the expression of Ki67 antigen in routinely processed tissue specimens. Pr oliferative activity in colonic carcinomas was scored by the percentage of positively stained cells. Labelling indices were estimated in 5 crypt compa rtments in apparently normal colonic mucosa adjacent and distant to the tum our in mucosal samples of controls from both population groups and in adena matous polyps from Europeans. The mean age of African patients with adenoca rcinoma was markedly lower than in European counterparts (48.6 yrs vs. 66.4 yrs). The overall proliferative activity in cancerous tumours of Africans was higher than in Europeans. The labelling indices were lower in all compa rtments in normal colonic mucosa in Africans. Overall increase of the label ling indices in adjacent and distant to the tumour mucosa noted when compar ed to the mucosa of healthy individuals. No such differences were detected between indices in the mucosa adjacent and the mucosa distant to the armour . Proliferative activity in the mucosa adjacent to adenoma was also higher than in normal mucosa from healthy individuals. Adenomas with mar ked dyspl asia showed higher and diffuse proliferative activity, when regular adenoma s shown superficial labelling only. Relatively young age, lack of detectabl e evidence of adenoma-carcinoma sequence and low proliferative activity in all compartments of mucosa from healthy individuals indicate different etio pathogenesis of colorectal carcinoma in rural Africans.