We detected the positive expression of STAT3 protein in 45.00% of 80 TETs, compared with 5.00% in 20 para-tumorous normal tissues with significant significance (P < 0.01), implying the possible role of STAT3 protein in oncogenesis and development of TET and its potential value as a parameter in molecular biology in diagnosis of TET. The gene discussed is STAT3; the disease is thymic epithelial neoplasm.