Biologic characterization of human bone tumors IX. Occurrence of macrophages.

Fifty bone tumors were investigated using immunohistological methods for an assessment of the amount and nature of macrophage infiltration. Polyclonal antibodies against lysozyme, alpha 1-antichymotrypsin, and alpha 1-antitrypsin were used as markers, besides certain monoclonal antibodies against blood monocytes and mature tissue macrophages. Particularly high macrophage infiltration was found in malignant fibrous histiocytomas, giant cell-containing osteosarcomas, giant cell tumors of bone, and aneurysmal bone cysts. Moderate infiltrates were seen in some highly malignant osteosarcomas, in fibrosarcoma, and in chondroblastoma. A low macrophage content was observed in some osteosarcomas, in Ewing's sarcomas, chordomas, fibrous dysplasias, aggressive fibromatoses, and cartilage tumors. Osteoclast-like giant cells showed distinctly positive reactions with the monoclonal antibody against mature tissue macrophages. In fibrohistiocytic tumors (MFH, giant cell tumor, non-ossifying fibroma) only macrophages gave positive reactions with those antibodies, whereas the reaction of spindle-shaped tumor cells was always negative. These results strongly indicate that the macrophages found in bone tumors (including those of fibrohistiocytic type) result from reactive infiltration. The autochthonous tumor cells are most probably derived from local mesenchymal cells, and are thus cytogenetically unrelated to the infiltrating macrophages.