Favorable Reproducibility of Ki-67-Labeling Index between Core Needle Biopsy and Surgical Materials in Mammary Carcinoma: Reproducibility Influenced by Hot Spots, a High Ki-67 Labeling Index, and the Total Length of Biopsy Material

Aims: The reproducibility of Ki-67 between core-needle biopsies and surgical materials has not been well documented in the literature, although the concordance affects the utility of the Ki-67 labeling index based on the core-needle biopsy materials, which indicates the need for preoperative chemotherapy. The aim of this study was to reveal the reproducibility of Ki-67 between both materials and the cause of discrepancies. Methods and Results: We analyzed 137 cases of invasive carcinoma of the breast and the compared Ki-67-labeling index between core-needle biopsy and surgical materials. The Ki-67-labeling index of biopsy and surgical specimens ranged from 1% to 85% (median: 13%) and 1% to 80% (median: 12%), respectively. The discrepancy of Ki-67-labeling ranged from 0% to 55% (median: 4%) and could be calculated by the tumor size, hot spots of surgical materials, a high Ki-67-labeling index based on the core-needle biopsy materials, and the total length of core needles, respectively. Conclusions: The concordance rate of the Ki-67-labeling index between core-needle biopsies and surgical materials was favorable, so we can use each Ki-67-labeling index of core-needle biopsies as a marker for preoperative chemotherapy. Factors affecting the index discrepancy were hot spots, a high Ki-67-labeling index, and the total length of biopsy material. Judgements on the subtypes and clinical procedures of invasive breast carcinoma could be made comprehensively based on not only the Ki-67-labeling index but also the existence of hot spots and histological grade.