Myofibroblastoma of the breast revisited: An etiologic association with androgens?

Myofibroblastoma of the breast is an uncommon benign stromal tumor encountered predominantly among elderly men. Histologically, myofibroblastoma is a well circumscribed tumor comprised of bipolar spindle cells arranged in short fascicles traversed by collagen bundles. Eased on previous histological, immunohistochemical, and ultrastructural observations, this tumor is thought to be derived from myofibroblasts. The pathogenesis df myofibroblastoma is unknown. Given the demographics of this lesion, the established trophic effect of steroid hormones, and the potential diagnostic utility of hormone receptor analysis in differentiating spindle cell tumors, we immunohistochemically tested for estrogen and androgen receptors in a host of spindle cell lesions including myofibroblastoma of the breast Five cases reported herein of histological confirmed myofibroblastoma obtained from male and female breasts each showed strong nuclear antibody staining fdr the androgen receptor, not seen in four cases of leiomyosarcoma, three cases of fibromatosis, three cases of dermato-fibrosarcoma protuberans, and two cases of monophasic synovial sarcoma. We postulate that the androgen receptor or its ligands may be pathological,ly related to the development of myofibroblastoma of the breast and diagnostically useful in differentiating it from other spindle cell lesions. Copyright (C) 1998 by W.B. Saunders Company.