Primary T-cell malignant lymphoma of the breast is rare, accounting for only 0.04%-0.5% of all malignant breast tumors. We report a case of primary T-cell malignant lymphoma of the breast, together with a review of the Japanese literature. A 49-year-old woman seen at the hospital because of a palpable left breast tumor was suspected to have breast cancer by clinical examinations before surgery. According to the LSG classification, the tumor was diagnosed as diffuse lymphoma derived from the large size cell type, and T cell type by immunohistochemical examination. Postoperatively, the patient received chemotherapy (VEPA). On the 8th month after the operation, she developed metastases to the tibial bone and axillary and cervical lymph nodes. After temporary symptomatic remission and a decrease of the lesion with additional chemotherapy (VEPA+VP16), she died of multiple bone metastasis 32 months after the diagnosis. T-cell lymphoma is often resistant to chemotherapy and the prognosis of this disease is poor.