ESR1 and breast cancer: ERBB2 amplification, germline BRCA1/2 mutations, PIK3CA mutations, and ESR1 mutations were mainly classified as tier I-A according to ESCAT in advanced BC whereas agnostic genomic alterations (NTRK1/2/3 fusions, MSI-H/dMMR, RET fusions, BRAF mutations, FGFR1/2/3 fusions or mutations and TMB-H) were classified as tier I-C according to ESCAT's list of tumor-agnostic genomic alterations.