Abstract

Myofibrosarcoma of the breast is a rare malignant mesenchymal tumor that has been reported in only four well documented cases so far. We report a case of myofibrosarcoma of the breast in an 88-year-old man who complained of a palpable mass for 1 year. Microscopically, the tumor consisted mainly of spindled cells, arranged in irregular fascicles and embedded in broad bands of dense hyalinized collagen. It showed ill-defined border infiltrating the adjacent adipose tissue, moderate cellular pleomorphism, and high mitotic rate (8~9/10 HPF). Immunohistochemical study confirmed myofibroblastic differentiation of the tumor cells with diffuse strong reaction for vimentin, smooth muscle actin, and fibronectin.

• Keywords: Myofibrosarcoma;Breast;