In conclusion, these data suggested a pivotal role of AhR in thyroid cancer tumorigenesis and confirmed the importance of the IDO1-kynurenine-AhR pathway not only in mediating an immunosuppressive microenvironment but also in favoring the acquisition of a mesenchymal phenotype that could promote invasiveness and metastasis. The gene discussed is IDO1; the disease is thyroid gland carcinoma.