[A biological and morphological study of ovoid and spindle cells in malignant fibrous histiocytomas]

To clarify the histogenesis of malignant fibrous histiocytoma (MFH), ovoid and spindle cells, the major components of this tumor, were biologically and morphologically studied using the following methods: (1) flow cytometric nuclear DNA analysis, (2) argyrophil staining for nucleolar organizer regions (Ag-NORs), (3) separation of MFH cells into the two types described above using a flow cytometric cell sorting system, (4) electron microscopic morphological observation, and (5) immunohistochemical examination. Specimens were obtained from 24 cases of soft-tissue MFH and 7 cases of MFH in the bone, which were treated in our institute. In ovoid cells, aneuploid pattern was shown by nuclear DNA analysis and high proliferation activity was found on Ag-NORs staining. Ultrastructural analysis showed that the ovoid cells had malignant characteristics and were presumedly histiocytic in origin. Immunohistochemical examination also, supported histiocytic origin. However, spindle cells were not identified as malignant tumor cells by the various methods described above. Although the histogenesis of MFH remains to be elucidated, these findings provide interesting information.