Thyroid Cancer

Thyroid Cancer

 

Thyroid cancer is the most common endocrine malignancy and represents 1% of all malignancies.

Epidemiology

  • Incidence
    • 9/100,000 per year
  • Age
    • Incidence increases with age
  • Gender
    • Affects females more frequently than males, but male gender associated with worse prognosis 

Risk Factors

  • Childhood radiation
  • Familial syndromes
    • Multiple endocrine neoplasias – MEN 2
  • Family history of thyroid cancer

Pathophysiology

  • Classification based on tumor cell type
    • Papillary
      • Incidence – 80% of thyroid malignancies
      • Tumor growth
        • Slow, local spread
      • Prognosis – excellent
    • Follicular
      • Incidence – 5-10% of thyroid malignancies
      • Gender – F:M; 3:1
      • Age of onset – 50 years
      • Risk factors – iodine deficiency
      • Tumor growth – greater risk of hematogenous spread
        • Includes variant called Hürthle cell cancer
      • Prognosis – excellent if no hematogenous spread  
    • Medullary (C-cell)
      • Incidence – 5-10% of thyroid malignancies
      • Risk factors –  MEN 2A and 2B, RET oncogene
      • Tumor growth – more aggressive
        • Elevated calcitonin is a marker
      • Prognosis – good
    • Lymphoma
      • Incidence – 2/1,000,000
      • Gender – F:M; 4:1
    • Anaplastic
      • Incidence – 2% of all thyroid malignancies
      • Gender – F:M; 3:1
      • Age of onset – 6th and 7th decade
      • Tumor growth – poorly differentiated
      • Prognosis – poor due to aggressiveness of disease

Clinical Presentation

  • Enlarging thyroid
  • Thyroid nodule
  • Metastasis – hoarseness, neck node involvement

Diagnosis

  • Imaging studies
    • Ultrasound
    • Tissue biopsy – fine needle aspirate
      • BRAF V6000E mutation testing for prognostication

Disease Monitoring

  • Sequential circulating thyroglobulin levels for papillary and follicular thyroid cancer
  • Sequential calcitonin levels
    • Calcitonin levels >100 pg/mL may occur in medullary thyroid carcinomas (MTC), leukemias and myeloproliferative disorders
    • Provocative testing (calcium) is suggested in patients with MTC if calcitonin is not clearly diagnostic
    • Calcium infusion alone, with peak calcitonin >120 pg/mL in women or >265 pg/ mL in men, indicates MCT or C-Cell hyperplasia (C-Ch)
  • RET oncogene – presence of familial syndrome

See Also