Figure 1 shows a flowchart of the literature screening process. All eight articles reported on the expression of STAT3 in thyroid cancer tissue and normal thyroid tissue. Six reports described the relationship between STAT3 expression in thyroid cancer tissue and lymph node metastasis, while three reported the relationship between STAT3 expression in thyroid cancer tissue and tumor TNM staging. Also, four articles explained the relationship between the expression of STAT3 in thyroid cancer tissue and age and gender.  Table 1 provides specific information from the included literature. This evidence concerns the gene STAT3 and thyroid cancer.