There were significant associations between CTLA-4 polymorphisms and two types of cancers (colorectal cancer: GA vs. AA, OR = 1.72, 95%CI = 1.13-2.60, Pheterogeneity< 0.001, P = 0.011; GG+GA vs. AA, OR = 1.52, 95%CI = 1.08-2.15, Pheterogeneity< 0.001, P = 0.017, Figure 4; thyroid cancer: G-allele vs. A-allele, OR = 1.50, 95%CI = 1.22-1.85, Pheterogeneity= 0.134, P< 0.001). Here, CTLA4 is linked to thyroid cancer.