Traditionally, genetic profiling focused on a limited set of mutations within well-characterized oncogenes such as TP53, PIK3CA, BRCA1, and HER2. However, recent large-scale studies, including The Cancer Genome Atlas and the METABRIC project, have expanded the understanding of breast cancer heterogeneity by identifying novel driver mutations, structural variants, and regulatory elements that were previously overlooked. The gene discussed is ERBB2; the disease is breast carcinoma.