The so-called malignant fibrous histiocytoma is histologically characterized by cellular atypia, nuclear pleomorphism, bizarre mitotic figures.

There is lack of immunoreactivity for any of the specific tumour markers. According to some authors the tumour basically represent diagnosis of exclusion.

Differential diagnosis:  Poorly differentiated variants of other sarcomas ; metastatic melanoma ; sarcomatoid (spindle cell and pleomorphic carcinoma).

Malignant fibrous histiocytoma (MFH) is among the most common soft tissue sarcomas of adult life, but rarely occurs elsewhere. We report an example of primary MFH of the lung and review 15 previously reported acceptable cases with current follow-up information. Histologically, the tumor in our case was pleomorphic with storiform and fascicular areas. Tumor cells showed positive immunostaining for alpha 1-antitrypsin, alpha 1-antichymotrypsin, and vimentin. Stains for desmin, cytokeratin, myoglobin, epithelial membrane antigen, S-100 protein, and lysozyme were negative. Electron microscopic study showed histiocyte-like, fibroblast-like, intermediate, and undifferentiated tumor cells. A variety of methods were used to treat these patients. Two patients survived for 5 or more years, two were alive and well at 8 and 12 months, respectively, two were alive with metastatic tumor at 3 and 18 months, respectively, and ten patients died of tumor, with an average survival of 1 year.

Primary malignant fibrous histiocytoma of the lung. Fine needle aspiration cytologic features.Acta Cytol. 1987 May-Jun;31(3):345-50

A case of primary malignant fibrous histiocytoma of the lung occurring in a 71-year-old woman is presented. The preoperative aspiration cytology showed a large-cell, undifferentiated, malignant neoplasm suggestive of carcinoma. Subsequent histologic examination revealed a primary malignant fibrous histiocytoma. The diagnosis was confirmed by electron microscopic and immunohistochemical studies. Cytologic features of this rare primary pulmonary sarcoma are discussed.

Malignant fibrous histiocytoma of the lung. Acta Pathol Jpn. 1985 Jul;35(4):945-50

A 75-year-old woman was admitted to a hospital for diagnosis of pulmonary infarction and died during treatment. An autopsy revealed a tumor 5 cm in diameter in the hilus of the left lung, spreading into the posterior mediastinum, and a metastasis was also found in the right lung. Histologically, this tumor consisted of two kinds of cells; one of fibroblast-like cells and the other of histiocyte-like cells, showing a storiform pattern. Furthermore, a positive staining for alpha 1-antitrypsin, but negative for CEA, keratin or S-100 protein was seen. Therefore, it was diagnosed as malignant fibrous histiocytoma (MFH) originating in the hilus of the left lung. In addition, many foci of hemorrhagic infarction due to metastasis and infiltration of the tumor into the pulmonary arteries were observed in the right lung. MFH is one of the rarest primary tumors of the lung.

Primary malignant myxoid fibrous histiocytoma of the lung. Light and ultrastructural examination with review of the literature. Arch Pathol Lab Med. 1984 Jan;108(1):49-54

We studied primary pulmonary malignant myxoid fibrous histiocytoma (MFH) by light and electron microscopy. Our ultrastructural examination supports the concept that MFH arises from a primitive mesenchymal cell that is able to differentiate toward fibroblastic and histiocytic lines. In the myxoid variant these cells produce a fine intracellular and extracellular amorphous material, probably representing mucopolysaccharide, which accounts for the myxoid stroma. We believe this is the first reported example of this rare but probably underreported sarcoma of the lung.

Primary malignant fibrous histiocytoma of the lung. A clinicopathologic and ultrastructural study of five cases.Cancer. 1984 Mar 1;53(5):1124-30

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.

Pulmonary malignant fibrous histiocytoma. Light and electron microscopic studies of one case.Chest. 1979 Feb;75(2):186-9

A malignant fibrous histiocytoma (MFH) arising in the lungs of a 51-year-old man was studied by light and electron microscopy. Features observed were identical to those of MFHs which occur in the skin and subcutaneous tissue and less commonly in other deep locations. By light microscopy, a storiform pattern with admixture of fibroblasts and histiocytes, as well as xanthomatous and giant cells, was noted. Undifferentiated tumor cells along with fibroblasts and histiocytes in different degrees of differentiation were identified ultrastructurally. These findings lend support to the concept that MFH is a sarcoma of primitive mesenchymal cell origin. The addition of the lung as another primary site for the development of this tumor is consistent with the view that MFHs may potentially arise in any part of the body.

Malignant fibrous histiocytoma of the lung.Cancer. 1979 Nov;44(5):1793-801

Two malignant fibrous histiocytomas arising primarily in the lung are described. The first was a large tumor of the right lower lobe in a 53-year-old man. The other tumor was found incidentally on routine roentgenograms in a 25-year-old woman and involved the left main pulmonary artery. The lesions could be resected but both patients developed early cerebral metastases. The neoplasms were predominantly fibroblastic, had a characteristic storiform pattern, and included large histiocytes with bizarre nuclei and a vacuolated cytoplasm. The ultrastructure of the cells in the fibroblastic areas was characterized by irregular nuclei and a cytoplasm with a well-developed endoplasmic reticulum and dilated cisternae. Some cells lacked the prominent endoplasmic reticulum of fibroblasts and others were characteristic histiocytes with numerous cytoplasmic lysosomes. The cases appear to be the first reported primary malignant fibrous histiocytomas of the lung.