Demonstration of alpha-1-antitrypsin and alpha-1-antichymotrypsin in fibrous histiocytomas using the immunoperoxidase technique.

Until recently, the diagnosis and classification of malignant fibrous histiocytomas (MFH) has been based on light- and electron-microscopic appearances. Tissue culture studies have led to the suggestion that these tumors have a common histiocytic origin. Using the immunoperoxidase PAP technique, a variety of soft-tissue tumors have been stained for the histiocyte markers alpha-1-antitrypsin (A1AT), alpha-1-antichymotrypsin (A1ACT) and lysozyme. A1AT and A1ACT are found to be useful specific markers for tumors of the MFH group whereas lysozyme is not a reliable marker for such tumors. The presence of these substances within the tumors supports the theory that they share a common origin from tissue histiocytes. Only a proportion of superficial skin histiocytomas stain for A1AT and A1ACT, raising the possibility that these are a heterogeneous group and do not share a common histogenesis with MFH.