ANGPT2 and neoplasm: To explore the relevance between Ang-2 expression and tumor size, tumors were classified based on the tumor size (cutoff value was 3 or 5 cm), and three studies were included, and the combined OR showed that Ang-2 expression was not significantly associated with tumor size [28, 31, 40], with a pooled OR estimate of 1.09 (95 % CI: 0.59–2.00, p = 0.78 and I2 = 0 %; Fig. 3d).