Syndecan-4 and fibronectin in osteosarcoma. Syndecan-4 (SDC4) and fibronectin (FN), which belong to the cell adhesion molecules, have been reported to correlate with tumour growth and invasion in various carcinomas. We aimed to investigate the prognostic value of these molecules in osteosarcoma.Using immunohistochemistry, we compared the expression of these molecules in high grade osteosarcoma to low grade central osteosarcoma, osteoid osteoma and normal bone. Further, the expression of SDC4 and FN were analysed with prognostic factors of high grade osteosarcoma.In high grade osteosarcoma, SDC4 was expressed in 50 of the 65 samples; of these, 32 of 65 showed strong expression profiles. FN was expressed in 46 of 65 samples, and 29 of 65 had evidence of strong expression of this molecule. SDC4 and FN expression were increased in high grade osteosarcoma as compared to other tissues. Strong SDC4 expression was associated with the occurrence of distant metastasis and a large tumour size, and strong FN expression was associated with the occurrence of distant metastasis. Strong expression of SDC4 or FN was associated with significantly shorter overall survival, respectively. CONSLUSIONS: Increased expression of SDC4 and FN may be underlying molecular alteration of osteosarcoma which accounts for more aggressive clinical behaviour.