CXCL8 and breast cancer: Analyzing the results in the subgroups of luminal A and B BC patients, CXCL8 again reached the highest values for all diagnostic features—in luminal A subgroup—SE 65.12%; PPV 66.67%, NPV 63.41%; in luminal B subgroup SE 74.47%, PPV 71.43%, NPV 68.42%.