Parenchymal leiomyoma of the breast. Report of a case and clinicopathological review.

We describe a 42-year-old woman with a solid breast mass of smooth muscle cell origin. Breast leiomyoma is an extremely rare benign tumour, with only 11 cases reported thus far. Various explanations have been offered with regard to its origin, such as hamartoma, embryonal migration from the nipple tissue, multipotent mesenchymal cells or the presence of myoepithelial cells originating from the breast ducts. The differential diagnosis for breast leiomyoma usually includes benign fibrous breast lesions, but leiomyosarcoma should definitely be ruled out. Surgical treatment consists of tumour excision with free margins. We discuss the tumour's clinical, pathological and immunohistochemical features, and review the current literature.