Recent approved biologics targeting the PD-1 (programmed cell death protein 1) and programmed-death-ligand-1 (PD-L1) immune checkpoint axis utilize IHC for PD-L1 expression as a complementary or companion diagnostic [6, 7], and PD-L1 immunoreactivity on tumor cells (TC) has been shown to decrease during tissue storage [1, 8, 9]. Here, PDCD1 is linked to neoplasm.