Myofibroblastoma of the breast: report of a case.

We report herein the case of a 36-year-old woman in whom a breast mass was diagnosed histologically and immunohistochemically as myofibroblastoma (MFB). The patient initially presented with a breast mass measuring 1.0 x 1.5 cm which was demonstrated by mammography as a well-circumscribed, round tumor with two coarse calcifications. On ultrasonography, the tumor showed slight shadowy internal echoes. Histological examination of an excisional biopsy specimen demonstrated a tumor consisting of spindle-shaped cells and broad bands of hyalinized collagen with cartilaginous and osseous components, but no epithelial components were observed. Immunohistochemically, the tumor cells were diffusely positive for alpha smooth muscle actin, and a diagnosis of MFB was made. A wide excision of the breast was performed as a secondary procedure, and the patient is well and free from recurrence 1 year after her operation. We present this case to stress the need for breast surgeons to be aware of the existence of MFB when considering the differential diagnosis of stromal lesions of the breast to avoid performing unnecessarily extensive procedures.