Expression in tumor cells was detected in medullary thyroid carcinoma, anaplastic thyroid carcinoma, and poorly differentiated thyroid carcinoma, while it was absent in benign lesions/tumors and differentiated carcinomas. Pleomorphic/giant cell morphology seemed to correlate with TIGIT expression in anaplastic thyroid carcinomas. This evidence concerns the gene TIGIT and poorly differentiated thyroid gland carcinoma.