Rhabdomyomatous thymoma.

A case of a thymic neoplasm with a prominent rhabdomyomatous component is presented. The patient, a 21-year-old asymptomatic man, had an anterior mediastinal mass found on routine chest radiographs. Surgical resection of an encapsulated anterior mediastinal mass was performed. Histologically, two distinct cell populations were apparent, one epithelial and the other myoid. Immunohistochemical studies using antibodies for keratin decorated the epithelial component of this lesion; antibodies for myoglobin and desmin strongly stained the myoid component.