In a recent retrospective study, high PD-1 expression (> 40% staining) in inflammatory cells was associated with worse overall survival (OS; hazard ratio, 3.36; 95% confidence interval, 1.00 to 12.96; P < 0.05) and trended towards worse PFS, whereas high PD-L1 expression in tumor cells (> 33% staining) trended towards worse PFS and OS indicating the crucial role of PD-1/PD-L-1 pathway in ATC [88]. Here, PDCD1 is linked to neoplasm.