Malignant phyllodes tumor with extensive lipomatous differentiation

Phyllodes tumors are uncommon neoplasms of the breast. Lipomatous differentiation of malignant phyllodes tumor is a rare stromal alteration of this fibroepithelial tumor, demonstrated as a fat-containing mass on imaging. We present the case of a 46-year-old woman who was diagnosed with a malignant phyllodes tumor of the breast that demonstrated extensive lipomatous differentiation.