PDCD1 and Hodgkins lymphoma: Unlike other programmed cell death 1 (PD-1) inhibitors or programmed cell death-ligand 1 (PD-L1) inhibitors (nivolumab, pembrolizumab and atezolizumab) approved by America Food and Drug Administration (FDA), sintilimab has been approved in China for classical Hodgkin lymphoma (8, 9).