SPP1 and neoplasm: The combined data showed that elevated OPN expression was associated with lymph node metastasis (OR = 2.03, 95% CI = 1.38–2.98, p < 0.001), TNM stage (OR = 1.83, 95% CI = 1.22–2.75, p = 0.004), depth of invasion (OR = 1.97, 95% CI = 1.22–3.17, p = 0.005), tumor size (OR = 1.43, 95% CI = 1.05–1.93, p = 0.022) and distant metastasis (OR = 2.66, 95% CI = 1.24–5.71, p = 0.012) (Table 3).