Mucosa-associated lymphoid tissue (MALT) lymphoma is an extranodal indolent lymphoma with histopatholigic features similar to those of marginal zone B-cell lymphomas. Primary breast MALT lymphomas were first described by Lamovec and Jancar as a low-grade B-cell lymphoma in 1987. Herein, a case is presented of a patient with primary MALT lymphoma of the breast. Issues in diagnosis and breast-conservation treatment, as it pertains to primary MALT lymphoma of the breast, will be discussed.