Abstract: Objective To explore the clinical features，diagnosis and treatment of 13 patients with primary breast diffuse large B cell lymphoma（PB-DLBCL）. Methods The clinical data of 13 patients with PB-DLBCL from Jan 2010 to Nov 2015 were retrospectively analyzed. Eight cases received breast mass excision，4 cases underwent modified radical mastectomy，and 1 case received unilateral mastectomy. Results All of the cases were female. The involved breasts were left-sided in 6 cases，right-sided in 6 cases，and bilateral breast was found in 1 case. The size ranged from 1.5 cm to 8.0 cm. Two cases were preoperatively diagnosed as breast fibroadenoma，1 case as giant fibroadenoma，and 10 cases as breast carcinoma. Thirteen cases were diagnosed as PB-DLBCL by using immunohistochemistry. According to Ann Arbor staging，10 cases were in stageⅠ，and 3 cases were in stage Ⅱ. Twelve cases received chemotherapy of CHOP or R-CHOP regimen after operation，and 1 case gave up treatment. The follow-up time ranged from 1 month to 5 years. During follow-up，2 cases relapsed，2 cases died，and 9 cases survived without relapse. Conclusion PB-DLBCL is not common in clinic，and mainly occurs in female. PBDLBCL is easily misdiagnosed by preoperative examination and intraoperative frozen section，and the exact diagnosis is confirmed by immunochemistry. Chemotherapy based comprehensive treatment is the main method for PB-DLBCL.