Paget disease is a type of adenocarcinoma that represents 1 to 4% of all breast cancers. Clinically patients present with eczema-like changes to the breast. The tumour is characterized by malignant cells (“Paget cells”) within the squamous epithelium of the nipple and surrounding skin. There commonly is an associated invasive breast carcinoma. Microscopically Paget cells are large with abundant pale cytoplasm, large nuclei, and prominent nucleoli. By immunohistochemistry, Paget cells are positive for CK7, CAM5.2, and HER2.