The expression of Novel Ca2+-binding proteins S100A1, S100A2, S100A4, S100A6 and S100B; an intermediate filament protein, glial fibrillary acidic protein (GFAP); and an extracellular matrix glycoprotein, tenascin were evaluated in chondro-osseous tumors. The tumor specimens obtained from surgery and routinely processed for paraffin embedding were evaluated. The tumors were histologically diagnosed as chondroma (n=2), osteoma (n=2), chondrosarcoma (n=3), osteosarcoma (n=6) and Ewing's sarcoma (n=2). Chondrocytes or chondrometaplastic cells in both benign and malignant tumors as well as undifferentiated round, spindle and elongated cells in chondrosarcoma and osteosarcoma showed an intense immunoreactivity for S100B and occasionally for S100A6, S100A1 and S100A4 but not for S100A2. The intensity of immunostaining for osteosar-coma was less intense than that for chondrosarcoma. S100B reactive cells were also reactive for GFAP, although the intensity of staining was less intense for GFAP. Reaction products for tenascin was seen in the matrix of neoplastic cartilage in chondroma and chondrosarcoma, and uncalcified osseous matrix in osteoma and osteosarcoma, and the immunoreactive areas of tenascin usually coincided with intensely reactive cells for S100B in neoplastic chondroid tissue. The results reasonably allowed to conclude that S100B may be a potential marker for the identification of chondroid cells in neoplastic lesions and the S100B containing cells may express GFAP and may be associated with an enhanced expression of tenascin in the tumor matrix, the functional significance of which is under investigation.
