Lysozyme and alpha 1-antitrypsin in giant-cell tumor of bone and in other lesions that contain giant cells.

We performed an immunohistochemical study of 24 giant-cell tumors of bone and 30 other lesions (fibrous histiocytoma, nonossifying fibroma, and giant-cell tumor of the tendon sheath) using lysozyme and alpha 1-antitrypsin as markers for histiocytic cells. The presence of histiocytic cells in giant-cell tumors of bone is confirmed by the finding of a positive reaction for alpha 1-antitrypsin in both multinucleate giant cells and mononuclear stromal cells in some cases. It is not clear whether the positive cells are to be regarded as neoplastic or reactive and alpha 1-antitrypsin is not considered as a diagnostically useful marker for giant-cell tumor of bone. In malignant fibrous histiocytoma, too, histiocytic cells could be identified by their positive reaction for alpha 1-antitrypsin; some of these cells had the morphologic features of tumor cells. Cells with a positive reaction for lysozyme were rarely found, except in giant-cell tumors of the tendon sheath.