AhR expression was evaluated by quantitative polymerase chain reaction (qPCR) in 90 papillary thyroid cancers (PTCs), 11 medullary thyroid cancers (MTCs), and 6 anaplastic thyroid cancers (ATCs) and by immunohistochemistry (IHC) in a subgroup of 41 of the 90 PTCs. Here, AHR is linked to medullary thyroid gland carcinoma.