Although we observed no significant differences, neither in the percentages nor in the mean expression of the other cytotoxic molecule; intracellular perforin, between patients and controls (92% vs. 91% and 21.21 vs. 22.84 for percentages and MFI, respectively), the findings collectively suggest less cytotoxic potency of the mentioned NK cell subsets in the patients with BC compared to HDs. This evidence concerns the gene PRF1 and breast cancer.