ERBB2 and neoplasm: In the multivariable analysis, factors associated with HR discordance were metastasis to bone only (OR = 2.54, [95% CI 1.15–5.63], p = 0,022) compared to brain metastases, MBC subtypes HR+/HER2− (OR = 0.05, [95% CI 0.03–0.08], p < 0.001) and HER2+ (OR = 0.37, [95% CI 0.23–0.59], p < 0.001) compared to HR−/HER2− and primary tumour treatments with endocrine therapy (OR = 3.08, [95% CI 1.96–4.82], p < 0.001) (Table 2).