ERBB2 and breast cancer: In patients with concordant expression in bilateral breast cancers, the majority were HR+ HER2− (143 patients, 82.2% out of 174 patients with concordant expression), followed by HR+ HER2+ (13 patients, 7.5%), HR− HER2− (11 patients, 6.3%) and HR− HER2+ (7 patients, 4.0%) (Table 3).