An evaluation of the cell cycle-associated monoclonal antibody Ki-S1 as a prognostic factor in primary invasive adenocarcinoma of the breast.

Immunohistochemical staining with the novel monoclonal antibody Ki-S1, believed to recognize a cell cycle-associated antigen, was investigated in 110 cases of invasive carcinoma of the breast. Immunoreactivity indices were compared with disease-free interval (DFI), overall survival, and a series of other prognostic indicators. Significant positive correlations were found between the percentage of strongly positive immunoreactive nuclei and tumour size, histological grade and type, vascular invasion, and mitotic count. A significant negative correlation was found with age. No significant correlation was found with either DFI or overall survival. Although a correlation with mitotic count does imply that the Ki-S1 antigen is cell cycle-associated to some extent, Ki-S1 does not appear to be a useful prognostic factor in human breast carcinoma.