CTLA4 and medullary thyroid gland carcinoma: However, PD-L1 positivity is associated with aggressive clinicopathological features (e.g., larger tumor size, lymph node or distant metastasis and higher TNM stage) (18, 19) and accounted as a predictor of structural recurrence and biochemical recurrence/persistent disease (19), and CTLA-4 expression is also correlated with advanced staging and structural recurrence-free survival (21), thus suggesting a possible prognostic role in the management of MTC (22).