MUC5AC and neoplasm: Mucinous breast cancer is a rare neoplasm of the breast, accounting for approximately 2% of all breast carcinomas.1 It is a type of invasive breast carcinoma characterized by clusters of epithelial tumor cells floating in pools of extracellular mucin.2 The initial presentation of such a neoplasm as a metastatic lesion in the lower alveolus is sporadic and can present as a diagnostic peril.