Primary malignant fibrous histiocytoma of the lung. A clinicopathologic and ultrastructural study of five cases.

Primary sarcomas of the lung are rare malignant neoplasms which have usually been classified as fibrosarcomas or as leiomyosarcomas. Only five cases of primary malignant fibrous histiocytoma (MFH) of the lung have previously been reported in the literature. The authors reviewed 10 cases of primary pulmonary sarcoma of the lung seen at their institution during the last 12 years, and five of these cases met the morphologic criteria for the diagnosis of MFH. The morphology in these cases is identical to MFH of other body locations, and shows a combination of fibroblast-like and histiocyte-like cells at both the light and electron microscopic level. By electron microscopic examination there was no evidence for anaplastic carcinoma, rhabdomyosarcoma, or leiomyosarcoma. Of the three patients with adequate follow-up, one patient is alive without evidence of disease at 10 years, one died at 5 years without evidence of recurrent sarcoma, and one died at 7 months with liver metastasis. Two other patients are alive without recurrence at 8 months and 1 year, respectively, following surgery. Because MFH is primarily a tumor of the soft tissues of the extremities, patients with MFH of the lung must be carefully evaluated to rule out a metastatic origin. The reported prognosis in patients with primary MFH of the lung is poor, but early surgical resection does offer the possibility of a cure.