Malignant phyllodes tumor of the breast: review of the literature and case report of stromal overgrowth.

Cystosarcoma phyllodes constitutes only 0.3-0.9% of all breast tumors. The term "sarcoma" was initially used because of its fleshy appearance, a more modern term is Phyllodes tumor (PT). The behavior of PT constitutes a spectrum from benign and locally recurrent to malignant and metastatic. In a general surgical series, 6.2% of the tumors were malignant. The microscopic appearance of PT is that of epithelial elements and connective tissue stroma. Malignancy is determined by characteristics of the stroma. The metastatic spread of malignant PT is mainly hematogenous to lung, with infrequent lymphatic involvement. Wide local excision with 2 cm margins is the treatment of choice. In 20% of both benign and malignant cases, PT will locally recur. There is no proven benefit of radiation or chemotherapy, although radiotherapy may be useful in selected cases. We present a case of a sarcomatous overgrowth in a malignant phyllodes tumor involving multiple histologic types.