Benign Fibrous Histiocytoma of the Skin: An Immunohistochemical Analysis of 30 Cases

Abstract

In this study the immunohistochemical analysis of distinct morphologic variants of benign fibrous histiocytoma (BFH) of the skin was performed with immunoperoxidase technique for both lysozyme and alpha-1-antitrypsin (A1AT). Thirty cases including cellular, fibrous and xanthomatous variants of BFH were selected. Out of the total 6 cases (20%) showed positive staining only for A1AT, 3 cases (10%) only for lysozyme and 10 (33.3%) for both markers. Thus, 19 cases (63.3%) showed positive staining for one of both markers. Positive staining was higher in the cellular variant than the fibrous and xanthomatous types. Negative staining of tumors of definite histiocytic morphology may be interpreted as a variable enzymatic expression of different histiocytic activation and/or undetectable enzymatic content by the current techniques. These results are in accordance with our previous evolutional hypothesis of BFH which considered the cellular tumors as functionally more active variants evolving to less cellular, more fibrous and less active types. Current histogenetic concepts about this controversial group of skin neoplasms are discussed.