In Case 14 (ER-negative/HER2-positive) we identified an enrichment in the signatures related to APOBEC-mediated mutagenesis (signatures 2 and 13) [20], which was previously described as enriched in metastatic tumors compared to primary tumors, in the context of HER2-negative breast cancers [32]. This evidence concerns the gene ERBB2 and metastatic neoplasm.