Background and objectives Methods The reasons behind the removal of the biopsy tract in osteosarcomas are not well known, and studies about tumor seeding in the biopsy tract have generated conflicting results. This study is designed to evaluate the presence and possible clinical significance of tumor cell seeding in the biopsy tract of osteosarcomas. We prospectively evaluated 55 cases of osteosarcomas for tumor cell seeding and other clinical and pathologic prognostic parameters. Results Conclusions Eleven cases (20%) involved microscopic tumor foci in the biopsy tract. The higher local recurrence rates (P = 0.005) and worse recurrence-free survivals (P = 0.009) were observed in patients with tumor cell foci in the biopsy tract. Mitotic rate, tumor cell pleomorphism, and matrix production in main tumor foci were higher in cases with tumor seeding (P = 0.047, P = 0.012, and P = 0.005, respectively) Tumor seeding in the biopsy tract is a fact in osteosarcomas. The higher local recurrence rates are more likely to occur in cases with tumor seeding.