COMPARISON OF QUANTITATIVE AND SEMIQUANTITATIVE METHODS OF ASSESSING MIB-1 WITH THE S-PHASE FRACTION IN BREAST-CARCINOMA

Different methods of assessing cell proliferation in breast cancer are currently being evaluated. Inherent qualities are required for such m ethods to be used on a routine basis in a pathology laboratory. Such q ualities include high sensitivity and specificity in recognizing proli ferating cells, simplicity in execution, and reproducibility. The MIB- 1 antibody permits the immunohistochemical detection of the Ki67 antig en in fixed and paraffin-embedded tissue sections. The aim of our stud y was to compare a semiquantitative and quantitative method of assessi ng MIB-1 immunostaining with the S-phase fraction (SPF) determined by flow cytometry in a series of 112 breast carcinomas. The median semiqu antitative MIB-1 score (SQ.MIB-1) in our series was 27.5%. The median quantitative MIB-1 score (B.MIB-1) was 563 positive neoplastic cells p er square millimeter of tumor, and, when corrected by the volume perce ntage nuclei (C.MIB-1), 2844 positive nuclei per square millimeter of total nuclear area. These three indices were strongly correlated to th e SPF (r = 0.73, 0.72, 0.72, n = 78), respectively for SQ.MIB-1, B.MIB -1, and C.MIB-1. MIB-1, assessed quantitatively or semiquantitatively, correlated with the Scarff, Bloom, and Richardson grade, including th e mitotic index and nuclear grade, as well as with the progesterone re ceptor status, SQ.MIB-1 determination was easier and faster than B.MIB -1 and C.MIB-1 determination. A high correlation was found for SQ.MIB- 1 results between two observers in this series (r = 0.92, n = 112), bu t the SQ.MLB-1 repeatability coefficient was 17.6%. Semiquantitation o f MIB-1 is strongly correlated to the SPF and is an easy and rapid met hod of assessing cell proliferation. More studies are necessary for ad ditional assessment of its reproducibility and its prognostic value in breast cancer.