[Formation of giant cells in oral squamous cell carcinoma during bleomycin treatment: enzymehistochemical, electronmicroscopic and ultrahistochemical investigations (author's transl)].

During treatment of keratinizing squamous cell carcinomas with bleomycin tumor cells are devitalized by keratinization, while simple necrosis plays a minor role. Connected with this process is a marked resorptive granulomatous inflammation with numerous macrophages which is followed by a fibrous organization. In the border region of the keratinized tumor areas many multinucleated giant cells appear. The nature of these giant cells was the subject of controversy. Enzyme histochemical, electronmicroscopic, and ultrahistochemical investigations in three cases of advanced squamous cell carcinoma of the oral cavity prove that the giant cells which are formed during bleomycin treatment are not multinucleated tumor cells, but multinucleated macrophages. The enzymatic pattern is similar to macrophages with a high content of acid phosphatase and aminopeptidase. The ultrastructure of the giant cells is characterized by lysosomes with acid phosphatase activity, pinocytotic vesicles, and cytoplasmic projections on the cell surface with signs of macroendocytosis. The tumor cells show an epithelial differentiation with desmosomes, tonofibrils, and keratohyaline granula. The giant cells are formed by fusion of mononucleated (monocytogenic) macrophages. The fusions seem to be related to the functional status of the cells. It is possible, that the macrophages and the giant cells have an additional immunologic function. This is suggested by the frequent association of giant cells with lymphocytes. The importance of these facts for the evaluation of the action of bleomycin and the consequences for its therapeutic use are discussed. A combination with methods causing a dedifferentiation of the tumor or suppression of the immunologic defense seems to be problematic.