HIF1A and bone neoplasm: To further explore the relationship between HIF-1α expression and the prognosis of patients with bone tumor, subgroup analyses of OS (Table 3 and Additional file 3: Figure S2) and DFS (Table 4 and Additional file 4: Figure S3) were performed to stratify by region, histological type, the number of cases, follow-up time, or the quality of included articles.