Description

Thyroid malignant neoplasia is an autologous growth of thyroid nodules with potential for metastases:

• Papillary carcinoma:
  • Most common variety, 60–70% of thyroid tumors
  • Peak incidence in the 3rd–4th decades
  • 3× more common in women
  • May be associated with radiation exposure
  • Tumor contains psammoma bodies.
  • Metastasizes by lymphatic route (30% at time of diagnosis)
  • Multicentric in ≥20%, especially in children
• Follicular carcinoma:
  • 10–20% of thyroid tumors
  • Peak incidence in 5th decade of life
  • Incidence has been decreasing since the addition of dietary iodine.
  • Metastasizes by the hematogenous route
• Hürthle cell carcinoma (variant of follicular with poorer prognosis):
  • Usually in patients >60 years
  • Radioresistant
  • Composed of distinct large eosinophilic cells with abundant cytoplasmic mitochondria
  • Variant of follicular carcinoma with worse prognosis
• Medullary thyroid carcinoma (MCT):
  • Arises from parafollicular cells, C cells
  • Multiple endocrine neoplasia (MEN) syndromes 2A and 2B occur within the first 2 decades of life.
  • 3–4% of all thyroid tumors
  • 25–35% are associated with MEN syndromes (2A more common than 2B), which can be familial or sporadic.
  • Calcitonin is a chemical marker.
  • RET proto-oncogene mutation is screen; family members who carry the RET gene should consider early prophylactic thyroidectomy.
• Anaplastic carcinoma:
  • 3% of thyroid tumors
  • Usually in patients >60 years
• Other: Lymphoma, sarcoma, or metastatic (renal, breast, or lung)
• System(s) affected: Endocrine/Metabolic
• Synonym(s): Follicular carcinoma of the thyroid; Papillary carcinoma of the thyroid; Hürthle cell carcinoma of the thyroid; Anaplastic cell carcinoma of the thyroid

Geriatric Considerations
Risk of malignancy increases at >60 years.

Pediatric Considerations
>60% of thyroid nodules are malignant.

Epidemiology

• 10/100,000 per year in the US
• Deaths: 6/1 million per year in the US
• In 2012, estimated 56,460 new cases and 1,780 deaths from thyroid cancer in the US
• Predominant age: Usually >40 years
• Predominant sex: Female > Male (2.6:1).

Risk Factors

• Family history
• Neck irradiation (6–2,000 rads): Papillary carcinoma
• Iodine deficiency: Follicular carcinoma
• Multiple endocrine neoplasia syndrome: Medullary carcinoma
• Previous history of subtotal thyroidectomy for malignancy: Anaplastic carcinoma
• Asian race

• Familial polyposis of the colon, Turcot syndrome, and Gardner syndrome with the APC gene, 5q21
• Medullary: Autosomal dominant with MEN syndrome
• BRAF mutation
• RET oncogene

General Prevention

• Physical exam in high-risk group
• Calcium infusion or pentagastrin stimulation test screening in high-risk MEN patients
• Screen for RET proto-oncogene in groups at risk for MCT.

Etiology

Unknown

Commonly Associated Conditions

Medullary carcinoma: Pheochromocytoma, hyperparathyroidism, ganglioneuroma of the GI tract, neuromata of mucosal membranes