Primary malignant fibrous histiocytoma of the pleura. A case report.

An uncommon primary malignant fibrous histiocytoma (MFH) of the pleura is described. At light microscopy the tumor was characterized by a 'storiform' pattern of growth, with numerous multinucleated giant cells. Immunohistochemistry showed an intense, diffuse immunostaining for alpha-1-antitrypsin, focal for lysozyme. Ultrastructurally, histiocyte- and fibroblast-like cells and cells with intermediate features were present; moreover, it was possible to demonstrate the presence of mesenchymal 'stem' cells. Findings are discussed, also with respect to histogenesis of MFH.