Primary nonepithelial malignancies of the breast comprise an important minority of breast neoplasms, including primary breast sarcomas, therapy-related breast sarcomas, the phyllodes tumors, and primary breast lymphomas. With widespread mammographic detection of breast lesions, these tumors represent critical elements of the differential diagnosis of even benign-appearing lesions. Each has a distinct clinical profile, including presentation, available therapeutic options, and prognosis, further underscoring the importance of timely recognition. The increasing incidence of breast carcinomas and the subsequent therapy thereof may be contributing to an increase in the number of therapy-related breast tumors. This review discusses various features of these uncommon malignancies and their treatment, with the goal of increasing understanding of their clinical behavior and management.