Statistical methods
Microsoft Excel 2017 (Microsoft, Redmond, WA, USA) was used to establish the database, and SPSS version 24.0 statistical software (IBM Corp., Armonk, NY, USA) was used to analyze the differences among the groups. The chi-squared test was used to compare frequency data between groups, and the differences between groups was considered to be statistically significant when P < 0.05. The immunohistochemical staining scores for CD3, CD4, CD8, PD-1, and PD-L1 in the 36 patients were analyzed.