A multicenter study showed that RET pathogenic variants correlated with the tumor size; variants affecting codon C634 being associated with larger tumors compared with those involving codon C618 (1.85 ± 1.11 versus 0.89 ± 0.67 cm, p = 0.004) and with higher calcitonin levels as well (333.9 ± 314.5 versus 84.5 ± 201.9 ng/mL, p = 0.030) [41]. The gene discussed is CALCA; the disease is neoplasm.