Clinical Presentation of Medullary Thyroid Carcinoma

  • Sporadic MTC (75% of all cases):
    • Typically occurs between the fourth to sixth decade of life:
      • However, patients with hereditary disease:
        • Present earlier
    • Patients with MTC who present with a palpable thyroid nodule:
      • 70% will have cervical lymphadenopathy
      • 15% to 20% will have palpable cervical lymphadenopathy.
    • Pain or aching:
      • Is also a common symptom of MTC
    • Local tumor invasion may produce symptoms of:
      • Dysphagia, dyspnea, or dysphonia
    • Patients with extensive metastatic disease frequently develop:
      • Diarrhea:
        • Which may result from:
          • Increased intestinal motility and impaired intestinal water and electrolyte flux:
            • Due to high calcitonin levels
      • About 2% to 4% of patients develop:
        • Cushing syndrome:
          • As a result of ectopic production of ACTH
  • Classic MEN2A is the most common variant of MEN2 (95% of the cases):
    • Most patients carry germline RET mutations in:
      • Codons 609, 611, 618, or 620 of exon 10
      • Codon 634 of exon 11
    • Almost all patients develop MTC:
      • But pheochromocytomas have the highest penetrance in patients with:
        • Codon 634 mutations:
          • 52% by age 50
          • 88% by age 77
        • These adrenal tumors:
          • Are almost always benign
          • Are usually multicentric
          • Are associated with diffuse adrenal nodular hyperplasia
      • HPT:
        • Is usually mild and may involve one to four parathyroid glands.
        • RET codon 634 mutations:
          • Are associated with a penetrance of up to 30% for PHPT, whereas it ranges from 2 to 12% for the remaining mutations.
  • Cutaneous lichen amyloidosis (CLA):
    • Can occur sporadically or in an inherited manner:
      • Either separately or in the context of MEN2A
    • The skin lesions of CLA in MEN2A:
      • Are most apparent in the dermatomes corresponding to T2 to T6:
        • Scapular region of the back
    • The classic symptom is:
      • Itching:
        • That worsens in times of stress
        • Improves with sun exposure
    • The lesions are incited by notalgia paresthetica:
      • A sensory neuropathy of the dorsal spinal nerve:
        • May occur prior to MTC
    • CLA is almost exclusively found in patients with:
      • The codon 634 mutations (exon 11)
      • Although cases have also been reported in patients with:
        • Codon 804 mutations
      • Pheochromocytomas and PHPT in CLA patients:
        • Occur at frequencies similar to classic MEN2A
  • In patients with MEN2B:
    • MTC often presents in infancy and is usually highly aggressive
    • Approximately 75% to 90% of MEN2B cases occur in patients:
      • Having de novo RET mutations:
        • Whereas 10% to 25% occur in families with:
          • Known history of MEN2B
    • About 95% of MEN2B individuals:
      • Have codon M918T mutations (exon 13) – Highest risk (HST)
        • The remaining 5% have codon A883F mutations (exon 15) – High risk (H):
          • The MTCs in codon A883F tend to be less aggressive
    • Pheochromocytomas develop in:
      • About 50% of MEN2B patients
    • These individuals also have a typical appearance that includes:
      • Eye abnormalities:
        • Thickened and everted eyelids
        • Mild ptosis
        • Thickened corneal nerves
      • Marfanoid body habitus
      • Long narrow facies
      • Pes cavus
      • Pectus excavatum
      • High-arched palate
      • Scoliosis
      • Slipped capital femoral epiphyses
      • Mucosal neuromas
      • Diffuse ganglioneuromatosis of the aerodigestive tract
        • Leading to bloating, intermittent constipation, diarrhea, and even intestinal obstruction
    • Some patients have atypical MEN2B:
      • Which presents later in life:
        • Around 20 to 30 years of age:
          • These patients have double RET germline mutations:
            • Occurring in tandem on the same allele:
              • Usually V804M and either Y806C, S904C, E805K, or Q781R