Comparison of monoclonal antibody Ki-67 reactivity with grade and DNA flow cytometry of breast carcinomas.

The reactivity of 95 breast carcinomas with the antibody Ki-67, which recognises a nuclear antigen in proliferating cells, has been assessed and compared to their histological grade and, for 47 tumours, DNA index and S-phase content. The effects of freezing and section handling on the stability of the nuclear antigen have been assessed. Evidence of nuclear staining was seen in 56% of carcinomas, with a range of positive cells from less than 1% to 60%. Cytoplasmic rather than nuclear staining was observed in 26% and 18% of carcinomas were negative. A significant correlation was observed between the presence of nuclear staining and poorer histological grade and higher S-phase content, and between the percentage of positive nuclei and S-phase content, but not grade. Three groups of carcinomas were identified: those in which Ki-67 reactivity, grade and S-phase content were similar; ones in which there was prominent nuclear reactivity with Ki-67 but low grade and S-phase content; and a group showing the converse. These patients will be followed to assess which of these three markers of proliferation is of greatest prognostic value.