ESR1 and breast neoplasm: Three-quarters of triple-negative BCs harbour at least one amplicon [31], however, their recurrence rates are lower than those of high-level CNAs found in ER-positive/ HER2-negative and HER2-positive BC subtypes (e.g. ERBB2-amplicon in HER2, and CCND1 and FGFR1 in luminal breast tumours [57]).