Proliferative activity of normal and neoplastic colonic mucosa in population groups with high and low risk for colorectal carcinoma.Anticancer Res. 1998 Nov-Dec; 18(6B):4641-4.AR
Europeans have a high incidence of colorectal cancer in comparison to Africans. Lack of detectable sequence adenoma-colorectal carcinoma in Africans may suggest the development of adenocarcinoma is de novo. The aim of this study is to assess colonic mucosal proliferative activity in various pathological 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 Africa) and 27 urban Europeans (Poland) and from apparently normal rectal mucous membrane from the age and sex matched each population group (28 and 25 samples respectively). In addition, 32 resected adenomatous polyps were examined in Europeans as well. The MIB 1 monoclonal antibody was used to assay the expression of Ki67 antigen in routinely processed tissue specimens. Proliferative activity in colonic carcinomas was scored by the percentage of positively stained cells. Labelling indices were estimated in 5 crypt compartments in apparently normal colonic mucosa adjacent and distant to the tumour, in mucosal samples of controls from both population groups and in adenomatous polyps from Europeans. The mean age of African patients with adenocarcinoma 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 compartments in normal colonic mucosa in Africans. Overall increase of the labelling indices in adjacent and distant to the tumour mucosa noted when compared to the mucosa of healthy individuals. No such differences were detected between indices in the mucosa adjacent and the mucosa distant to the tumour. Proliferative activity in the mucosa adjacent to adenoma was also higher than in normal mucosa from healthy individuals. Adenomas with marked dysplasia showed higher and diffuse proliferative activity, when regular adenomas shown superficial labelling only. Relatively young age, lack of detectable evidence of adenoma-carcinoma sequence and low proliferative activity in all compartments of mucosa from healthy individuals indicate different etiopathogenesis of colorectal carcinoma in rural Africans.