This rare breast tumor forms from the stroma [STROM-ah] (connective tissue) of the breast, in contrast to carcinomas which develop in the ducts or lobules. Phyllodes [FI-lodes] tumors are usually benign, but on rare occasions have been found to be malignant (cancerous with the potential to metastasize). These occurrences are extremely rare, with fewer than 10 women dying each year as a result of this breast cancer.
Phyllodes tumors do not respond to hormonal therapy and are less likely to respond to other breast cancer treatments such as chemotherapy or radiation therapy. As a result, benign phyllodes tumors are treated by removing the mass and a narrow margin of the surrounding breast tissue. Malignant phyllodes tumors are removed in the same manner with a wider margin of breast tissue, or by mastectomy.