Others, however, have proposed that, particularly in the neoadjuvant chemotherapy setting, that HER2-low tumours can be considered a “new subgroup of breast cancer by standardised IHC, distinct from HER2-zero tumours” highlighting a lower pathological response rate in hormone receptor positive lesions compared to HER2 negative lesions and differences in prognosis [27]. This evidence concerns the gene ERBB2 and neoplasm.