Malignant phyllodes tumor following irradiation of the breast.

This is a case report of malignant phyllodes tumor (cystosarcoma phyllodes) which appeared 15 years following medical irradiation of the breast for presumable carcinoma which had not been histologically or cytologically confirmed prior to treatment. Histology of the phyllodes tumor disclosed remnant of fibroadenoma in one area, and it is believed that the latter gave rise to the malignant phyllodes tumor within the field of irradiation. In view of recent popularity of the limited surgery and postoperative irradiation in treatment of breast carcinoma the possibility of malignant transformation of fibroadenoma left in situ is raised.