In this study fresh frozen tissue samples of benign osseous
tumors (five non-osteogenic
fibromas, one fibrous dysplasia, one chondromyxoidfibroma),
tumors of uncertain
biological behaviour (eight cases of
histiocytosis X, two
giant-cell tumors), and of malignant intraosseous
tumors (two
malignant fibrous histiocytomas, two
malignant histiocytosis, four
osteosarcomas, one
chondrosarcoma and two Ewing
sarcomas) were studied with a panel of
monoclonal antibodies reactive with monocyte/macrophages and various types of dendritic cells. In addition,
tumors were further defined with a broad spectrum of
antibodies against filamentous
proteins and lymphocyte
differentiation antigens. The specimens were stained with a triple-layer immunoalkaline
phosphatase protocol.
Tumors stained with these
antibodies could be roughly divided into two groups. The first group comprised
tumors with one predominant cell population reactive with one particular
monoclonal antibody. In this group, cases of
histiocytosis X were found to be consistently labelled with CD-1
antibodies. The
giant-cell tumors showed a very homogeneous staining with certain monocyte/macrophage
antibodies (Ki-M8). Nevertheless, even in these
tumors, heterogeneity was demonstrated by the occurrence of cells with monocytic differentiation in
histiocytosis X and conversely by the occurrence of cells with
differentiation antigens of the dendritic cell system in
giant-cell tumors. An exception has to be made for the two cases of
malignant histiocytosis examined. These
tumors were selectively labelled with
antibodies against monocyte/macrophages (Ki-M8, IOM-1). The second group comprised
tumors showing a high degree of heterogeneity demonstrated by the varying amounts of
tumor cells reacting with the applied markers of the monocyte/macrophage and dendritic cell systems. In most cases it was difficult to ascribe labelled cells to the
tumor cell population as opposed to an "innocent bystander" inflammatory cell population. This distinction was especially difficult in
malignant fibrous histiocytomas underlining the current concept that these
tumors are of primitive mesenchymal rather than true histiocytic origin.