(fih-LOH-deez TOO-mer)

A rare tumor that usually forms in the connective tissue of the breast. Phyllodes tumors tend to grow quickly and get large, but they rarely spread to other parts of the body. Most are benign (not cancer), but some may be malignant (cancer) or borderline (in between benign and malignant). Phyllodes tumors are usually removed by surgery, but they can come back. They are most common in women between 40 and 50 years of age. Also called CSP and cystosarcoma phyllodes of the breast.