Giant myofibroblastoma of the male breast: a case report and literature review.

Myofibroblastomas are soft-tissue neoplasms that are thought to arise from myofibroblasts. They are mostly observed in males 41-85 years of age; however, this lesion also occurs in women. The usual clinical presentation is a unilateral painless lump that is not adherent to overlying or underlying structures. Microscopically, myofibroblastomas can be divided into 5 subtypes: classical, epithelioid, collagenised, cellular, and infiltrative. Mammary ducts and lobules are absent in the typical histological subtypes and the adjacent breast parenchyma may form a pseudocapsule. The majority of myofibroblastomas are immunoreactive for CD34, desmin, smooth muscle actin, and vimentin and are negative for cytokeratin and S-100 protein. We present a case of a giant myofibroblastoma arising in the background of gynecomastia in an adult male.