PDCD1 and primary central nervous system lymphoma: On the other hand, the efficacy of PD-1 or PD-L1 blockades in non-Hodgkin lymphoma (NHL) has shown disappointingly low response rates, except for some specific subsets of NHL, such as primary mediastinal B cell lymphoma (PMBCL) [13], primary testicular lymphoma (PTL) or primary central nervous system lymphoma (PCNSL) [14,15].