He R, et al. - Considering the crucial role played by programmed death-1 (PD-1) pathway in tumor host immunity evasion, researchers evaluated PD-1 and PD-L1 expression by immunohistochemistry in 39 chronic lymphocytic leukemia/small lymphocytic lymphoma, 15 DLBCL-RT, and 26 other DLBCL. In DLBCL-RT, a biological continuum from prolymphocytes/paraimmunoblasts in CLL/SLL PCs to the neoplastic B-cells was observed. The characteristic PD-1 expression makes it a potential surrogate marker for determining clonal relatedness to CLL/SLL in DLBCL-RT. This might be having significant prognostic and therapeutic implications.