PDCD1 and classic Hodgkin lymphoma: Koh et al. [5] also came to that understanding and, based on recent studies that reported the associations between PD-L1 or PD-L2/PD-1 pathways and pro-angiogenic genes, examined the relationship of PD-L1, PD-L2, PD-1, VEGF expression, and microvessel density (MVD) in cHL.