The RET proto-oncogene mutation associated with the highest risk of early aggressive medullary thyroid carcinoma, necessitating prophylactic thyroidectomy within the first 6 months of life, belongs to which MEN2 variant?
- A MEN2A with C634R mutation
- B FMTC with codon 609 mutation
- C MEN2B with M918T mutation ✓
- D MEN2A with codon 634 mutation only
Correct answer: C. MEN2B with M918T mutation
Explanation
The M918T mutation in exon 16 of RET is associated with MEN2B and carries the highest risk (ATA category D, 'highest risk'), mandating prophylactic thyroidectomy within the first 6 months of life — ideally within the first month. Medullary thyroid carcinoma in MEN2B has the most aggressive behaviour, earliest onset, and worst prognosis. Codon 634 mutations in MEN2A are high risk (ATA category C) but recommend thyroidectomy by age 5, not within 6 months.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.