PDCD1 and B-cell non-Hodgkin lymphoma: In contrast to other B-cell lymphoma entities, PD-L1 and PD-L2 are rarely expressed by FL tumor cells [112], and SVs of PD-L1/PD-L2 are infrequent, detected only in 4% of cases [93]; however, PD-1 is abundantly expressed in the ME, though with variable expression patterns [113].