CD274 and Hodgkins lymphoma: Although PD-L1 is frequently expressed in malignant cells, the regulatory mechanisms are not uniform and a number of complex signaling pathways are involved in its regulation in HL and NHL (with the exception of ENKL), such as MEK/ERK, NF-jB, PI3K/Akt, JAK/STAT and p38 MAPK (32,33).