HAVCR2 and medullary thyroid gland carcinoma: In a large cohort study of MTC, positive TIGIT, LAG-3, CTLA-4, PD-1, and TIM-3 expression was detected in 6 (3.0 %), 6 (3.0 %), 25 (12.5 %), 27 (13.5 %), and 96 (48.0%) patients, respectively, with a positive correlation between TIM-3, PD-1, and CTLA-4 expression.