PDCD1 and primary cutaneous T-cell non-Hodgkin lymphoma: Clinical trials of anti–PD-1 antibodies revealed that the PD-1 expression status or deletion was unrelated to anti–PD-1 therapy outcomes in CTCL patients (4), implying that factors other than PD-1 expression determined the tumor-suppressive activity of the PD-1 signaling pathway in CTCLs.