PDCD1 and undifferentiated pleomorphic sarcoma: We previously performed immunohistochemistry (IHC) staining of lymphocyte markers and immune checkpoint proteins programmed death-ligand 1 (PD-L1) and programmed cell death protein 1 (PD-1) in several sarcoma subtypes and found that a subset of undifferentiated pleomorphic sarcoma (UPS) and myxofibrosarcoma (MFS) contained tumour infiltrating lymphocytes (TILs) as well as PD-L1 and PD-1 expression [22].