Thyroid malignancies

Thyroid malignancies are most commonly primary thyroid cancers but can rarely be metastatic deposits.

Pathology

Classification

Thyroid malignancies can be categorized into the following key subtypes:

• primary thyroid cancers
  • ​papillary thyroid carcinoma: 60-80% of carcinomas
  • follicular thyroid carcinoma: 10-20%
  • medullary thyroid carcinoma: 5%
  • anaplastic thyroid carcinoma : 1-2%
• thyroid lymphoma: ~2.5%
  • primary thyroid lymphoma
  • secondary thyroid involvement with lymphoma
• metastases to the thyroid: 1%
• squamous cell carcinoma (rare) ⁴
  • primary
  • secondary
    • direct invasion from head and neck squamous cell carcinoma
    • metastatic disease

Risk factors

• head and neck irradiation (see radiation-induced thyroid cancer)
• family history of thyroid cancer
• age <30 or >60 years
• male
• >2 cm 

Staging

For primary thyroid tumors see: staging of thyroid cancer.