ERBB2 and breast cancer: Latent class analysis identified four endophenotypes of breast cancer: favourable biology, with biologically favourable and locally contained tumours; HGHR- (“high grade HR-“), with the highest grade tumours on average and largely HR- receptor subtypes, yet limited disease spread and good survival; HR+ bone, described by HR+/HER2- subtype, lymph node and isolated lung metastases, and good survival; distant organ spread, which represents the vast majority of metastatic burden and death despite less aggressive tumour grade and HR/HER2 status than the HGHR- cohort.