PDCD1 and classic Hodgkin lymphoma: In classical Hodgkin lymphoma (cHL), PD-L1 is commonly overexpressed by Hodgkin and Reed–Sternberg (HRS) cells [1], and increased PD-1+ tumor infiltrating leukocytes (TILs) [2,3,4] and PD-L1 expression on HRS cells [3,5] have been associated with worse outcome.