Thyroid Cancer

 

Clinical Background

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

Epidemiology

  • Incidence – 9/100,000
  • Age – incidence increases with age
  • Sex – M<F, 1:2 or more
  • Prognosis – male sex associated with worse prognosis 

Risk Factors

  • Childhood radiation
  • Familial syndromes
    • Syndromic with predominance of nonthyroidal tumors (predominant autosomal dominant inheritance)
      • PTEN mutation – hamartoma syndrome
      • Camey complex (Cowden syndrome)
      • Gardner syndrome
      • Peutz-Jeghers syndrome
      • Werner syndrome
      • Multiple endocrine neoplasias – MEN2
      • Familial adenomatous polyposis
    • Nonsyndromic or familial with preponderance of non-medullary thyroid carcinoma
      • Familial papillary thyroid carcinoma
      • Familial papillary thyroid carcinoma associated with renal neoplasia
      • Familial multinodular goiter
      • Familial non-medullary thyroid carcinoma type 1
  • Family history of thyroid cancer

Pathophysiology

  • Classification based on tumor cell type
    • Papillary
      • Prevalence – 70-80% of thyroid malignancies
      • Sex – M<F
      • Tumor growth
        • Slow, local spread; high correlation between tumor size and extension
      • Prognosis – excellent
    • Follicular
      • Prevalence – 5-20% of thyroid malignancies
      • Sex – M<F, 1:3
      • Age – onset is 50 years
      • Risk factors – iodine deficiency
      • Tumor growth – greater risk of hematogenous spread to lungs, bone, brain, bladder and skin
        • Includes variant called Hürthle cell cancer (4-5%)
      • Prognosis – excellent if no hematogenous spread of thyroid cancer
    • Medullary (C-cell)
      • Prevalence – 3-10% of thyroid malignancies
      • Two types – sporadic, familial
      • Age
        • Sporadic – onset in older adults
        • Familial – onset in children
      • Risk factors – MEN2A and 2B, RET oncogene (familial predisposition in 20-25% of cases)
      • Tumor growth – more aggressive with early metastases to lung, bone, mediastinum, abdominal nodes
        • Elevated calcitonin is a marker
      • Prognosis – good if discovered early; aggressive if found to be part of familial syndrome
    • Anaplastic
      • Prevalence – 2% of thyroid malignancies
      • Sex – M<F, 1:3
      • Age – onset in 50s
      • Tumor growth – poorly differentiated; aggressive growth with metastases to lungs, pleura, bone and brain
      • Prognosis – poor due to aggressiveness of disease
    • Lymphoma
      • Incidence – 2/1,000,000
      • Sex – M<F, 1:4

Clinical Presentation

  • Enlarged thyroid
  • Thyroid nodule
  • Hoarseness, enlarged cervical adenopathy – metastases