AHR and head and neck squamous cell carcinoma: The present study, at least based on the size of our cohort, rejected all four AHR, CYP1A1, CYP1A2, and CYP1B1 genes as having any statistically significantly detectable contribution to HNSCC in smokers; further, we first found a false-positive observation—that the CYP1B1 haplotype ACTTGATC might be associated with HNSCC risk in our cohort (Table 7).