HER2 overexpression in ductal carcinoma in situ is associated with ipsilateral breast cancer recurrence after conservative surgery

Ductal carcinoma in situ (DCIS) refers to the proliferation of abnormal epithelial cells in the basement membrane of the mammary duct system without invasion to stroma (1). It is a non-obligatory precursor of subsequent invasive cancer. Due to the inherent heterogeneity of DCIS, distinguishing the high-risk DCIS cases from low/moderate-risk lesions are still a challenge