TDO2 and neoplasm: Although the correlation analysis of IDO1, IDO2, TDO2, and IL4I1 with PD‐L1 in the TCGA cohort was quite different from the IHC results in our present study, several reasons might explain the difference: (1) The expressions of IDO1, IDO2, TDO2, and IL4I1 in the TCGA cohort are from the whole tissues, which includes intra‐tumor cells, non‐tumor epithelial cells, and immune cells.