COMPARISON OF MIB-1 PROLIFERATION INDEX WITH S-PHASE FRACTION IN HUMAN BREAST CARCINOMAS

The MIB-1 antibody has been raised against recombinant parts of the Ki -67 antigen and, unlike Ki-67, has wider application to routinely fixe d specimens. The aim of this study was to compare the usefulness of MI B-1 with S-phase fraction (SPF) as a measure of proliferation. A total of 75 patients with operable breast cancer were studied, 44 (median a ge 56 years) before any treatment and 31 (median age 68 years) after p rimary medical hormonal therapy. Sections from formalin-fixed paraffin -embedded tissue were stained with the MIB-1 antibody and a percentage score of positively stained cells obtained. SPF was measured by flow cytometry in fine-needle aspiration samples taken from the same lesion in each patient. Median MIB-1 score was 9% and median SPF was 11.1%. A close correlation was found between MIB-1 score and SPF (rho = 0.59, P < 0.0001). There was a difference in the strength of the correlatio n found between the no treatment group and the treatment group, howeve r, 95% confidence intervals for the rho values overlapped. indicating that there was no significant statistical difference. When analysed fo r ploidy status a correlation was found only in aneuploid rumours. MIB -1 immunostaining can be used as an effective method of assessing prol iferation in human breast carcinomas. This can be done using simple, w idely available technology and provides the opportunity to perform lar ge-scale retrospective analyses of archival material.