Malignant Phyllodes Tumor of the Breast

Phyllodes tumors of the breast are rare lesions that historically have been presumed to be related to fibroadenomata, largely by virtue of the entities' histologic similarities. We report four cases of malignant phyllodes tumors (cystosarcoma phyllodes) of the breast, three showing liposarcomatous differentiation and one showing chondrosarcomatous and osteosarcomatous differentiation, each of which had demonstrable histologic continuity with benign fibroadenomata; one patient had a prior and concurrent history of multiple bilateral fibroadenomata. We postulate that fibroadenomata and phyllodes tumors (benign, borderline, and malignant) may constitute a spectrum of one stromal disease analogous to mammary epithelial hyperplasia, atypical hyperplasia, in situ, and invasive carcinoma. Int J Surg Pathol 3(1):17-22, 1995