PDCD1 and peritoneal neoplasm: Compared with primary peritoneal neoplasms group, the percentages of CD45 + PD-1+, CD3 + PD-1+, and CD3 + CD4 + PD-1 + were increased in the secondary peritoneal neoplasms group (the p value was respectively 0.010, 0.044, and 0.040, Fig. 4A), while PD-1 expressed on CD3 + CD8 + T cells had no difference (p = 0.112, Fig. 4A).