Additional immunohistochemical stains (such as ER, CK5, and p63 or other myoepithelial markers) can aid to distinguish the lesion and determine whether the biopsy contains a pure papilloma, an atypical papilloma, or a papillary DCIS when there is any diagnostic uncertainty [4]. The gene discussed is ESR1; the disease is ductal breast carcinoma in situ.