ERBB2 and breast cancer: In our pilot survey, we observed that some ERBB2+ BC patients experienced lapatinib treatment failure and rapid disease progression; this was frequently observed for those with an in-frame insertion mutation of ERBB2 [NM_004448.3, ERBB2: c.2339_2340-ins-CGGCTCCCC (p. Pro780_Tyr781insGlySerPro)].