This study reviewed 26 women who had resection of a malignant cystosarcoma phyllodes. Clinical presentations were palpable mass, 25; pain, 11; and ulceration, 2. Definitive surgical therapy was radical mastectomy (RM), 2; modified radical mastectomy (MRM), 14; total mastectomy (TM), 4; and partial mastectomy (PM), 6. Tumors ranged in size from 1-20 cm (median, 7 cm). Eight patients developed recurrent disease after 10-45 months. Local recurrence was more likely after TM and PM than after MRM and RM (P < 0.05). Patients who developed local recurrence only were treated by wide re-excision, and all such patients are alive with no evidence of disease at 5-25 years. Only one of 16 patients undergoing axillary dissection had involved lymph nodes. Four patients whose tumors ranged from 5-8 cm and who underwent one RM and three MRM developed systemic recurrence; all died of their disease after 15-48 months.1) Although there is a higher local recurrence after PM and TM as compared with MRM and RM for malignant cystosarcoma phyllodes, the local recurrence can be treated with wide excision without affecting long-term survival; 2) systemic recurrence was not related to size or extent of resection; 3) axillary dissection does not predict for or prevent recurrence.