HHLA2 and metastatic malignant neoplasm in the lymph nodes: Meta-analysis of the association between HHLA2 expression and clinicopathological parameters showed a significant relationship between high HHLA2 expression and old age (OR = 1.30, 95% CI: 1.03–1.63), lymph node metastasis (OR = 1.99, 95% CI: 1.41–2.81), and vascular invasion (OR = 1.69, 95% CI: 1.18–2.42).