Tumour IDO expression not significantly correlated with histology, clinical/nodal stage or tumour differentiation, but positively associated with density of FOXP3+ TILs (P = .028). High IDO expression was an independent predictor of poor DFS (HR = 3.973, P = .026) and OS (HR = 3.258, P = .029). This evidence concerns the gene IDO1 and neoplasm.