Myofibroblastoma in the Irradiated Breast.

Myofibroblastoma after wide excision and radiation therapy for intraductal (duct carcinoma in situ) carcinoma is reported. Myofibroblastoma is a benign tumor, largely composed of myofibroblasts arranged in fascicular clusters with interspersed bands of hyalinized collagen, which is well circumscribed and occurs predominantly in men. This is the first documented instance of a postradiation myofibroblastoma of the breast.