This finding can be explained by the association of distinct patterns of DNA copy number alteration with breast cancer subtypes: a “simple” type with few gains or losses in luminal A subtype, an “amplifier” type with focal high-level DNA amplifications in luminal B and HER2 subtypes, and a “complex” type characterized by numerous low-amplitude changes in triple-negative subtype26. This evidence concerns the gene ERBB2 and breast cancer.