Immunohistochemical diagnostic testing for programmed cell death ligand 1 (PD-L1 has been approved for targeted treatment of several major cancer types including non small cell lung cancer, NSCLC However, the semi quantitative scoring of PD-L1 expression is complex and requires training of pathologists to reduce inter and intra reader variability Here we present some of our data for a worldwide, expert led training in PD-L1 interpretation and scoring of NSCLC cases, conducted over a two year period, 2016 2017 using glass slides or equivalent digital images.