Radiation-induced malignant fibrous histiocytoma of the pulmonary artery.

We describe a malignant fibrous histiocytoma (MFH) of the pulmonary artery. The patient received, 25 years ago, at the age of 43 years, radiation therapy to the chest for squamous-cell carcinoma of the lung. We believe the patient's second tumor was induced by radiation and, to our knowledge, this case represents the first report of radiation-induced MFH of the pulmonary artery. The diagnosis was confirmed by findings from electron microscopy and extensive studies with immunohistochemical stains. We discuss the value of studies with immunohistochemical stains in the diagnosis and differential diagnosis of MFH. The presentation of this case underlines that MFH can occur in the pulmonary artery and may be--as is the MFH in other locations--induced by radiation.