Several molecular epidemiological studies of CDKN1A Ser31Arg SNP show conflicting results with some studies reporting increased risk association with tobacco related upper aerodigestive tract cancers,49 while showing a protective effect in human papilloma virus related cervical cancers.50, 51 The only study of this SNP in MTC has been reported by Barbieri et al27 in a small cohort of 45 sporadic MTC cases. Here, CDKN1A is linked to medullary thyroid gland carcinoma.