Ki-67 derived proliferative activity in colorectal adenocarcinoma with prognostic correlations

Cryostat sections from samples of 108 colorectal carcinomas were stained with the murine monoclonal antibody Ki-67, which is expressed in proliferating cells. Ki-67 immunoreactivity was assessed independently by two pathologists using a semi-quantitative method. There was excellent correlation between the two observers. Ten cases were assessed quantitatively by counting at least 2000 cells and there was a very good correlation between this method and the semi-quantitative method. The carcinomas showed a wide range of Ki-67 labelling, reflecting a variation in proliferative activity. The tumour labelling index ranged from 1 to 80 per cent positivity: there was also heterogeneity of labelling within many of the tumours. There was no correlation between Ki-67 derived proliferative score and known prognostic parameters, including Dukes stage, New Prognostic Classification grade, lymph node status, tumour differentiation, venous spread, invasive margin, lymphocytic infiltrate, and curative versus palliative surgery. Nevertheless, it is concluded that Ki-67 immunohistochemistry provides a reliable and reproducible method of assessment of proliferative activity in colorectal cancer. Ki-67 immunohistochemistry may have a clinical application in the selection of patients with colorectal cancers who might benefit from radiotherapy and/or chemotherapy, particularly those with unresectable or locally recurrent tumours.