Primary breast lymphoma is a rare form of extranodal lymphoma, defined by the presence of a primary lesion within the breast with or without regional nodal involvement but no other extra-mammary sites of involvement. It comprises diverse histologic subtypes, but diffuse large B-cell lymphoma is the most common. In this review, we describe in detail the clinical features, diagnosis and staging, pathogenesis, risk factors and therapy of primary breast diffuse large B-cell lymphoma. We consider choice and number of cycles of chemotherapy, the indications for radiotherapy and discuss the need for central nervous system prophylaxis. We also provide a brief overview of the less commonly encountered histologic subtypes including marginal zone, follicular, Burkitt and breast implant associated anaplastic large cell lymphoma. We conclude with a suggested treatment approach and potential areas of future research.