Differences in the Value of Proliferation Index (Ki67) and Immunophenotypes Between Invasive Breast Cancers With Respect to the Axillary Lymph Node Status

Introduction: Present study aimed to determine the frequency of invasive breast cancer (IBC) immunophenotypes in the General County Hospital Vinkovci, examine a difference between the ages of patients with respect to immunophenotypes and axillary lymph node (ALN) status, and determine differences in the frequency of positive ALNs with respect to immunophenotypes and the proliferation index (Ki67), regardless of the immunophenotype. Materials and Methods: A monocentre cross-sectional study which included 289 patients diagnosed with invasive breast cancer was conducted in the period from 1 January 2011 to 31 December 2018. The expression of IBC biomarkers was determined by immunohistochemistry. Results: The most common immunophenotype (41.54 %) was luminal B-like HER2-negative (LumB/HER2-). The mean age was 65.24 (± 12.04), with no age difference with respect to immunophenotypes (F = 0.64, P = 0.43) or ALN status (t = 1.59; P = 0.11). A total of 167 patients (58 %) had their ALNs removed, 66 % of which were positive. LumB/HER2- appeared to have significantly more positive ALNs compared to the luminal A-like immunophenotype (P < 0.01), while a difference in the size of primary tumours between metastatic breast cancers of these two immunophenotypes has not been detected (P = 0.17). ALNs were more likely to be positive in those tumours with Ki67 values higher than 20 % compared to the tumours in which Ki67 was lower than or equal to 20 % (P < 0.01). Conclusions: LumB/HER2- is the most prevalent IBC immunophenotype in patients in our institution and has significantly more positive ALNs compared to the luminal A-like immunophenotype. Also, metastases to ALNs, regardless of the immunophenotype, are more common in patients with Ki67 higher than 20 % than in those with Ki67 lower than or equal to 20 %