A case of primary marginal zone B-cell lymphoma in an elderly female patient is presented. Primary breast lymphomas are rare, comprising less than 1 per cent of all breast malignancies. These tumors have no clinical, pathologic, or radiologic pathognomonic features to distinguish them from breast adenocarcinoma. The diagnosis is usually made with an excisional biopsy, and more extensive surgery should be avoided. Delivery of radiation therapy and chemotherapy is tailored according to the histologic grade, stage of disease, and overall patient condition. This report summarizes the current knowledge reflected in the literature.