Introduction: Tumor-infiltrating lymphocytes (TILs) might be associated with host-cell mediated immunity, which could be partly reflected by peripheral blood cell counts. In addition, lymphocyte-predominant breast cancer (LPBC), which was defined as tumors having high TIL levels, showed a favorable prognosis among triple-negative breast cancer or HER2-positive breast cancer. We aimed to investigate whether peripheral blood cell counts are associated with LPBC. Methods: We evaluated the percentage of stromal TILs in breast cancer patients who underwent primary surgery, using the standardized methodology proposed by the international TIL Working Group. Lymphocyte-predominant breast cancer (LPBC) was defined as tumors having high TIL levels (≥50%). Peripheral blood cell counts including absolute neutrophil counts (ANC), absolute lymphocyte counts (ALC) and neutrophil-to-lymphocyte ratio (NLR) was obtained from pretreatment laboratory data. Result: Of the 810 patients, 132 (16.3%) had LPBC, and 678 (83.7%) had non-LBPC. In a comparison of 3 markers of peripheral blood counts, LPBC had a significantly lower mean ANC than non-LPBC (3,304 vs. 3,564; P = 0.023), but the other means were not different. In multivariable analysis, each 1K increment in ANC corresponded to an odds ratio of 0.790 (95% CI, 0.642 to 0.971) for LPBC. In the ER-negative and high-Ki67 subgroups identified by interaction tests, significant inverse correlations between continuous ANC and TILs were noted. Conclusion: Low peripheral ANC could be linked with LPBC, supporting the hypothesis that systemic immune cell counts might be associated with the tumor-immune microenvironment.
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