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Myofibroblastoma of the breast with diverse differentiations
1Department of Pathology, Jikei University School of Medicine, Tokyo, Japan.
Background:
The histogenesis of myofibroblastoma of the breast remains unknown.
Design:
Two cases of myofibroblastoma of the female breast were analyzed using light microscopy and immunohistochemistry.
Results:
The tumors were well circumscribed and predominantly composed of bland bipolar spindle cells and interspersed bands of hyalinized collagen. Additionally, one tumor contained a cartilaginous island, and the other contained a well-defined small nodule that consisted of fascicular arrangements of mitotically inactive atypical cells, simulating atypical leiomyoma. Both lesions contained a fatty element. Immunohistochemically, spindle tumor cells expressed desmin, alpha-smooth muscle actin, muscle actin, and CD34. The atypical cells were strongly and diffusely positive for all these markers. Both tumors were DNA diploid and had a moderate S-phase fraction. The patients have no evidence of disease 4 and 18 months after simple excision.
Conclusions:
Myofibroblastoma of the breast may be a benign mesenchymal neoplasm capable of diverse lines of differentiation.