A Case of Myofibroblastoma of the Left Breast

Abstract

Myofibroblastoma of the breast is rare and recognized as a benign mammary tumor of mesenchymal origin. We report a case of myofibroblastoma of the left breast in a 66-year-old woman. She visited our clinic, as she noticed a left breast tumor on the day before her visit. The oval elastic-hard tumor measuring 3.0×2.5cm was palpated in the ECD area of the left breast. A mild degree of concave at the nipple was noted. Mammography demonstrated a 2.3×2.0cm lobulated mass and partially obscure margin. Solid tubular carcinoma was suspected. Ultrasonography revealed a 2.3×2.7×2.5cm lobulated mass with low heterogeneous echoic area.
So we suspected the tumor to be malignant. Fine needle aspiration cytology revealed an inadequate finding with spindle-shaped cells without appreciable nuclei atypia. On a core needle biopsy, phyllodes tumor was strongly suspected. Excisional biopsy was performed and an oval well-circumscribed lobulated tumor was removed. Histological specimens revealed proliferation of spindle-shaped cells, and immunohisitochemistry revealed that the tumor cells were positive for actin, alfa-SMA and vimentin but negative for cytokeratin and S-100 protein. Therefore the tumor was diagnosed as myofibroblastoma.