Comparison between Ki-67 Index and S-Phase Fraction on Fine-Needle Aspiration Samples from Breast Carcinoma

Abstract

Background. Fine-needle aspiration (FNA) biopsy has been used increasingly in the diagnosis and biologic characterization of breast carcinomas in patients who receive preoperative chemotherapy. Because proliferative activity of breast carcinoma has been shown to be of prognostic significance, the authors compared immunocytochemical Ki-67 growth fraction and flow cytometric S-phase fraction (SPF), both evaluated on FNA samples. Methods. The proliferative activity of 134 FNA samples from primary breast carcinoma patients was studied using both immunocytochemistry with the monoclonal antibody Ki-67 and SPF determined by DNA flow cytometry. Results. Ki-67 and SPF were evaluable in 114 and 107 cases, respectively, and both were evaluable in 95 cases. Of the 134 FNA samples studied, 37% were diploid and 63% were aneuploid. The distribution of both Ki-67 and SPF was different in diploid and aneuploid tumors. The median Ki-67 value as well as the median SPF were significantly higher in aneuploid versus diploid tumors (p < 0.001). Median Ki-67 and SPF values were used to discriminate between low versus high proliferating tumors. The overall concordance between Ki-67 and SPF was 75% (p < 0.001). A good correlation was found between Ki-67 and SPF (correlation coefficient = 0.72; p < 0.001). Conclusions. The results of the current study suggest the Ki-67 growth fraction and SPF determined by FNA may be used as measurements of the proliferative activity of breast carcinoma. The authors recommend these determinations be used as preoperative procedures in patients with a cytologic diagnosis of breast carcinoma who are candidates for neoadjuvant chemotherapy and/or endocrine therapy.