Ki-67 as a prognostic marker in colorectal cancer but not in gastric cancer.

The growth of tumors is highly variable and this probably reflects even its clinical course. The monoclonal antibody Ki-67 recognises an antigen present in the nuclei of cells in all phases of the cell cycle except G0. In the current study, we examined by immunohistochemistry the proliferative activity, based on Ki-67 labeling index (Ki67LI), in formalin-fixed and paraffin-embedded sections of 152 tumors, being 70 gastric and 89 colorectal cancers. The results obtained were correlated with the clinicopathologic factors. The carcinomas showed a wide range of Ki-67LI, reflecting a variation in proliferative activity. The tumor labeling index ranged from 10 to 85 per cent positivity, being the mean level in gastric cancer tissue 0.52 and in colorectal cancer 0.44. There was also heterogeneity of labeling within many of the tumors. No significant correlation was found between Ki-67LI and sex, age, clinical stage in these cancers. In colorectal cancer, but not in gastric cancer, high levels of Ki67LI have been correlated with poor survival. Ki-67 staining is a simple and useful method for estimating proliferative activity. The importance of Ki-67 as an indicator of tumor behaviour is not clear. In colorectal cancer this index may be used as a marker of prognosis.