ERBB2 and breast cancer: When it comes to subtypes of breast cancer, CXCL1 gene amplification was observed in 1.20% (6/499) of luminal A breast cancer cases, 3.55% (7/197) of luminal B breast cancer cases, 7.69% (6/78) of HER2-positive breast cancer cases, and 1.17% (2/171) of basal breast cancer cases.