ERBB2 and breast cancer: As is known to us that brain metastasis occurs in 30%-50% of HER2-positive metastatic breast cancer and trastuzumab is unable to cross the blood–brain barrier [24, 25], nearly one-third of patients with HER2-positive breast cancer ultimately develop brain metastases after previous trastuzumab, and different mechanisms of action between trastuzumab and lapatinib [10, 12], switching mode with lapatinib might be a sensible therapeutic option for those with brain metastases.