Pediatric Medullary Thyroid Carcinoma: Clinical Presentations and Long-Term Outcomes in 144 Patients Over 6 Decades.

sMTC is primarily a RET-driven disease that represents 14% of childhood-onset MTC in this cohort. Pediatric sMTC patients are older, present with clinical disease at a more advanced TNM classification, and have more persistent disease at last follow-up compared with hMTC, but these differences disappear when comparing those presenting clinically. Somatic molecular testing should be considered in sMTC patients who would benefit from systemic therapy.