Medullary thyroid carcinoma (MTC) arises from parafollicular C cells and secretes calcitonin. In familial MTC associated with MEN2, the RET codon 634 point mutation confers the HIGHEST risk phenotype. Prophylactic thyroidectomy is recommended at what age in MEN2A patients with codon 634 mutation (ATA risk category C)?
- A Before age 10 years
- B Before age 5 years ✓
- C After age 18 years when molecular diagnosis is confirmed
- D Only after pentagastrin stimulation test becomes positive
Correct answer: B. Before age 5 years
Explanation
The ATA (American Thyroid Association) risk stratification for RET mutations guides timing of prophylactic thyroidectomy in MEN2. Codon 634 mutations (Cys634Arg/Tyr) are classified as ATA-C (high risk) and prophylactic thyroidectomy is recommended before age 5 years to prevent MTC, which can develop early in childhood in these patients. The highest-risk codon 918 mutations (MEN2B, ATA-D) warrant surgery within the first 6 months of life.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.