Niu et al. showed that in patients with papillary thyroid carcinoma (PTC), HHLA2 mRNA expression levels were significantly higher in PTC tissues than in normal tissues, and significant HHLA2 upregulation was uncovered in PTC cells compared with normal cells (p < 0.001) [48]. This evidence concerns the gene HHLA2 and thyroid gland papillary carcinoma.