On univariate competing risk analysis, the risk of IBTR was significantly higher when the index DCIS was diagnosed at a younger age, presented clinically, and of large size or of 3+ HER2 status, consistent with previous studies.32, 33 However, the lower rates of IBTR compared with CBC after BCS for DCIS patients whose margin was negative by the polygon method observed in our study are in sharp contrast with those in prior literature that consistently showed higher rates of IBTR than CBC following BCS with or without radiotherapy. The gene discussed is ERBB2; the disease is ductal breast carcinoma in situ.