Primary soft tissue sarcoma (STS) of the breast is a rare and heterogeneous disease. The rarity of this tumor limits most studies to small retrospective case reviews and case reports. The optimal treatment of primary STS of the breast can best be determined through multidisciplinary discussions prior to the initiation of therapy. Whether chemotherapy is indicated is primarily determined by tumor size. There is evidence that tumors larger than 5 cm are associated with an elevated risk of systemic failure and a poor prognosis. Negative surgical margins are more important for local recurrence and overall survival than is the extent of surgical resection. Thus, neoadjuvant chemotherapy should be considered in order to shrink the tumor and help obtain negative surgical margins. After surgical resection, patients with chemosensitive tumors should undergo additional adjuvant chemotherapy to treat micrometastatic disease. Patients with tumors less than 5 cm that are easily resectable should undergo complete resection to the extent required to provide negative surgical margins. Radiation therapy should be used to improve local control in cases in which the tumor is larger than 5 cm and in cases with positive surgical margins. The appropriate treatment of primary STS of the breast requires a multidisciplinary approach necessitating experienced surgeons, pathologists, radiotherapists, and medical oncologists.