PAS: periodic acid-Schiff; CK: cytokeratin; CEA: carcinoembryonic antigen; HER2/neu: human epidermal growth factor receptor 2; HMB: hydroxymethylbutyrate; HPE: histopathological examination; IHC: immunohistochemistry; MPD: mammary Paget’s disease; IgE: immunoglobulin E. This evidence concerns the gene ERBB2 and mammary Paget disease.