The concept of HER2-low was proposed by Paolo Tarantino et al., in 2020:HER2-low includes immunohistochemistry (IHC) 1+ and IHC 2+/In situ hybridization (ISH) (−) (Tarantino et al., 2020), which was also detailed in the 2022 Chinese Society of Clinical Oncology guidelines for the diagnosis and management of BC (Li and Jiang, 2022), and in 2023, the ESMO expert statement supported the consensus on the definition, diagnosis and management of HER2-low BC (Mathey-Andrews, 2024; Tarantino et al., 2023). This evidence concerns the gene ERBB2 and breast cancer.