However, given that some thymic carcinoma cells express PD-L1, which is used as a treatment biomarker of anti-PD-1 antibody in certain cancer types, we designed and conducted a single-arm, multicenter, phase II trial of nivolumab for the treatment of unresectable or recurrent thymic carcinoma: the PRIMER study (UMIN 000022007) (1). Here, PDCD1 is linked to thymic carcinoma.