IDO1 and neoplasm: The findings demonstrated that IDO1 had a moderate diagnostic accuracy (AUC between 0.6 and 0.9) for KIRP, STAD, UCEC, KICH, OSCC, LUAD, CESC, ESAD, CHOL, ESCA, HNSC, LIHC and THCA in predicting tumor or non-tumor prognosis, but a higher diagnostic accuracy (AUC > 0.9) for KIRH and GBM (Fig. 4M).