Keratin 7 and ERBB2 Negative Mammary Paget Disease Without an Underlying in Situ and Invasive Carcinoma.

We report a unique case of a post-menopausal female who presented with a lesion on the areola. A biopsy of the lesion demonstrated a pagetoid intraepithelial neoplasm suggesting a differential diagnosis of mammary Paget disease and pagetoid Bowen disease. Excision of the lesion confirmed the diagnosis of mammary Paget disease with typical histological appearance. This case is extremely rare since both keratin 7 and ERBB2 were negative, and there was no evidence of underlying in situ or invasive carcinoma.