[Malignant fibrous histiocytoma: an ultrastructural, histochemical and immunohistochemical study of 34 cases].

The microscopical and ultrastructural features of 34 cases of malignant fibrous histiocytoma were studied. Ultrastructurally, the malignant fibrous histiocytoma was composed of fibroblasts, histiocytes, intermediates, myofibroblasts, primitive mesenchymal, xanthomatous and multinucleated tumor giant calls. The histiocytes were confirmed by ACP and alpha 1-AT stainings. Both fibroblasts and myofibroblasts were pleomorphic in appearance, and some of them were often mistaken for histiocytes by LM. The multinucleated giant cells and xanthomatous cells may have derived from fibroblast, histiocyte or myofibroblast. This study supports the concept that the tumor arises from primitive mesenchymal cells which are capable of differentiating toward different cell lines.