A reduced risk of squamous cell carcinoma was seen with both HLA Class I (HLA-B*15 (OR = 0.55, P = 4.78 × 10−6)) and HLA Class II alleles (HLA-DQA1*0103 (OR = 0.69, P = 0.006), HLA-DRB1*13 (OR = 0.71, P = 5.27 × 10−4), HLA-DQB1*0603 (OR = 0.69, P = 0.007)). This evidence concerns the gene HLA-DRB1 and squamous cell carcinoma.