A case of reticulum cell sarcoma of the breast is presented who is a 38-year-old Korean house wife and she died at twelfth day after simple mastectomy, but unfortunately we couldn’t knave autopsy and also we had a literature review of primary reticulum cell sarcoma of breast. Primary lymphosarcoma of the breast is relatively rare malignant neoplasm and rapidly progressive, aggressive disease in the majority. Radical surgery with supplemental irradiation of the breast is recommended. This tumor is consisted of well circumscribed hard mashes, measuring 3.0 X 3.0cm to 4.5×4.0cm, which has partial adhesion to the chest wall and multilocular cystic changes measuring 10×4cm which contains hemorrhagic content.