According to the recent study, 80% of mature T/NK cell neoplasms and around 30% of mature B cell lymphomas were IDO positive in immunohistochemistry (Kim et al., 2020a), and upregulated IDO expression in DLBCL was associated with a poor prognosis (Sun et al., 2022). The gene discussed is IDO1; the disease is B-cell non-Hodgkin lymphoma.