However, lobular lesions in the B5a category behave biologically similar as their DCIS counterpart, have higher risk for local recurrence and progression to invasive cancer, are more often Her2 positive, and therefore, their clinical management is very similar to DCIS (WHO 2019; Wen and Brogi 2018; Shamir et al. 2019). This evidence concerns the gene ERBB2 and ductal breast carcinoma in situ.