Immunohistochemical identification of lysozyme and vimentin in an experimental malignant fibrous histiocytoma.

The immunoperoxidase avidin-biotin-peroxidase complex method was used to investigate the presence of histiocyte markers such as lysozyme, alpha-1-antitrypsin (A1AT) and alpha-1-anti-chymotrypsin (A1ACT) and of vimentin, a specific marker for mesenchymal differentiation, in a spontaneous and transplantable rat tumor of supposed fibroblastic-histiocytic origin. Positive staining was obtained for lysozyme and vimentin but A1AT and A1ACT were not demonstrable in any of the tumor sections. These results provide evidence for the fibro-histiocytic nature of the tumor studied and suggest its classification as a malignant fibrous histiocytoma (MFH).