This retrospective study aimed to evaluate the prevalence of occult contralateral disease and to identify clinicopathological factors associated with disease-free survival (DFS).<h4>Methods</h4>We retrospectively analyzed all surgical patients with sMTC at a tertiary academic center (2013-2025), excluding patients with hereditary MTC, RET mutations, or clinical evidence of MEN2. The gene discussed is RET; the disease is medullary thyroid gland carcinoma.