PDCD1 and synovial sarcoma: PD-1 and PD-L1 expression and the presence of CD8+ lymphocytes were assessed in primary osteosarcoma (n = 46), Ewing sarcoma (n = 32), alveolar rhabdomyosarcoma (n = 20), embryonal rhabdomyosarcoma (n = 77), synovial sarcoma (n = 22) and DSRCT (n = 11) and subdivided in negative (0–10 (%)), positive (10–50 (%)) or high positive (≥ 50 (%)) expression (Table 1 and Figure 1).