ERBB2 and neoplasm: Despite the FDA34 and the European Medicines Agency35 approvals of T-DXd for metastatic breast cancer following the DB-04 trial, it is widely agreed among ASCO/CAP and European Society of Medical Oncology (ESMO) that HER2-low does not represent a biologically distinct entity, but rather a heterogeneous group of tumours influenced by HER2 expression6,36.