ERBB2 and breast cancer: With the deepening of research, multiple subtypes of a particular type of breast cancer have been classified, such as Lehmann BD et al. [183], who classified TNBC into six subtypes, Jiang YZ et al. [184], who classified TNBC into four subtypes, and Jin X et al. [185], who classified HR + /HER2- breast cancer into four subtypes.