RADIOLOGY: BREAST: Case# 32942: PHYLLOIDES TUMOR. 35 year old female with a palpable mass. Close up from mammogram reveals a large well circumscribed mass. Phylloides tumor is a fibroepithelial lesion. It has also been called "giant fibroadenoma" and cystosarcoma phylloides. Although usually indolent and benign, up to 10 percent may metastasize. Mammographically phylloides tumors are large, well circumscribed lesions without calcification or spiculation.