The oral cavity is a rare site of metastatic lesions; however, metastatic breast carcinoma must be included in the differential diagnosis of tumors of that site in women. We describe a 54-year-old woman who presented with a lesion of the floor of the mouth that histologically resembled polymorphous low-grade adenocarcinoma of the minor salivary glands, which was eventually established to represent metastatic lobular breast carcinoma. The final diagnosis was based on comparison with a primary tumor resected 13 years earlier and immunohistochemical reactivity with antibodies to steroid receptors. Relevant aspects of lobular breast carcinoma, polymorphous low-grade adenocarcinoma, and metastatic oral cavity lesions are discussed.