[Electron microscopic study on malignant fibrous histiocytoma induced by local application of DMBA heterotransplanted in nude mice].

Though Malignant Fibrous Histiocytoma (MFH) has been regarded as a relatively common neoplasm of the mesenchymal soft tissues, the issue of character is largely unresolvable at present. Our department formerly reported that produced experimental MFH by administering 9, 10-dimethyl-1, 2-benzanthracene (DMBA) in male hamsters. In this study I have examined the fine structure of transplantation and heterotransplantation of MFH. The following results were obtained. 1. Five different types of cells were found in the MFH: fibroblast-like cells, histiocyte-like cells, undifferentiated cells, multinucleated giant cells and xanthomatous cells. 2. In histiocyte-like cells, nonphagocytic and actively phagocytic histiocyte-like cells could be distinguished. 3. The multinucleated giant cells could be found two types, fibroblast-like and histiocyte-like. 4. In transplantation, the histology of the original tumor was retained. 5. In heterotransplantation, the tumor was composed mainly of nonphagocytic histiocyte-like cells and undifferentiated cells. 6. The possibility is suggested that both principal cell types in this tumor may derive from the same undifferentiated stem cells.