MIB-1 index, S-phase fraction, mitotic figure count, and SBR histologic grading in invasive breast carcinoma: a comparative study

Abstract: Proliferative activity has been proven to be of prognostic significance in breast carcinoma. This study was performed to compare the different proliferative fractions in the Egyptian population and to define the most suitable one for daily routine use in our surgical pathology laboratories. The proliferative activity of 63 invasive ductal carcinomas was evaluated by immunohistochemical staining of paraffin-embedded tissue sections with MIB-1 rabbit polyclonal antibody and the heat-induced epitope retrieval method, flow cytometric determination of the S-phase fraction (SPF) on frozen tissues, and estimation of the Scarff–Bloom–Richardson (SBR) grading and mitotic figure count (MFC) on hematoxylin and eosin-stained tissue sections. Fifty-two percent of invasive ductal carcinoma were aneuploid. The mean values of MIB-1 index, SPF, and MFC were 17.7 ± 12.3, 4.9 ± 3.8, and 5.2 ± 4.5, respectively, for diploid tumors; while for aneuploid tumors, they were 58.6 ± 31.9, 19.9 ± 12.2, and 23.1 ± 16.9, respectively. These values were significantly higher in aneuploid versus diploid tumors (p < 0.0001). A close correlation was found between MIB-1 index, SPF, MFC, and SBR grading (p < 0.0001). In conclusion, in surgical pathology laboratories that cannot afford the costs of flow cytometry and/or immunostaining, proper SBR grading and MFC can provide an estimation of the proliferation fraction similar to the flow cytometric SPF and MIB-1 immunostaining.