NCCN Guidelines for Breast Cancer V.1.2021 include NGS and comprehensive genomic profiling (CGP) as a method of detecting actionable mutations and fusions such as BRCA1/2 mutations, PIK3CA mutations, ESR1 mutation, HER2 mutation, MSI-H status, and deficient mismatch repair (dMMR) [57]. Here, ESR1 is linked to breast cancer.