RET and medullary thyroid gland carcinoma: While some studies have suggested a putative role of the RET L769L variant with a higher risk of MTC and younger age of onset [121,122,123,124] as well as a higher risk of lymph node invasion [125], in contrast, a large case-control association study carried out on 585 sporadic MTCs, 1529 non-medullary thyroid cancers, and 989 healthy controls, Gemignani et al. reported that RET L769L allele frequency was lower in patients with MTC (OR = 0.70 95%CI [0.58–0.84], p = 1.9 × 10−4) and rare homozygotes showed a lower OR = 0.32 (95%CI [0.17–0.60], p = 2.3 × 10−4) [126].