ESR1 and breast cancer: Another contribution to the identification of the genes associated with responses to immunotherapy in TNBC was made by Sivapiragasam et al. They performed the comprehensive genomic profiling of 3831 metastatic breast cancers (1237 ER+, 1953 HER2+, and 641 TNBC) using FoundationOne CDx, an Illumina-based assay, to detect genetic alterations in 324 genes, as well as genomic signatures such as microsatellite instability (MSI) and tumor mutation burden (TMB).