Contribution of histiocytic cells to sarcomatous development of the gliosarcoma. An immunohistochemical study

The expression of glial fibrillary acidic protein, fibronectin (FN), factor VIII-related antigen (FVIII/RAG), and of three monohistiocytic markers, lysozyme, alpha-1-antitrypsin and alpha-1-antichymotrypsin was examined in five gliosarcomas (GS) by peroxidase-antiperoxidase immunostaining of formalin-fixed and paraffin-embedded specimens, and compared with vascular changes in 16 glioblastomas (GB). In contrast to GB, endothelial proliferations of GS were sheathed by sarcomatous tissue (perivascular sarcoma), which was contiguous with fibrosarcomatous areas. Cells with conspicuous intracytoplasmic FN content (FN+ cells) were seen in the vascular stroma of GB and dominated in the sarcomatous parts of GS. Most FN+ cells of GS were of varying size and shape and clearly neoplastic. Monohistiocytic markers were demonstrable in small infiltrating mononuclear cells as well as in many sarcomatous cells including FN+ cells. FVIII/RAG was restricted to lumen-lining endothelium and was not found in sarcomatous cells. These results suggest that a major part of sarcoma in GS is less likely to develop from proliferated endothelial cells than from histiocytic cells in the perivascular spaces of GB. By FN mediation, histiocytic cells might also guide and promote sarcomatous proliferations of other mesenchymal cells, leading to fibrosarcomatous development. Prominent monstrous giant cells of one GS seemed to be degenerating glioma cells.