Metastases to the thyroid

Metastases to the thyroid are an uncommon cause of thyroid malignancy. 

Epidemiology

Metastases to the thyroid represent 1.4-3% of all malignancies ⁵. In autopsy series, the incidence is ~10% (range 2-24%) ^1,5. 

Pathology

The most common sites of primary malignancy include (note these will vary by region) ^1,2,5:

• kidney
  • renal cell carcinoma (considered most common)
• lung
• head and neck
• breast
• gastrointestinal tract
  • esophageal cancer
  • colorectal cancer
  • gastric cancer ⁸
• skin
  • malignant melanoma
•  neuroendocrine tumor ⁶
• cholangiocarcinoma (rare) ⁷

Radiographic features

Ultrasound

Metastases to the thyroid most commonly have the following features ¹:

• hypoechoic lesion with poorly circumscribed margins (80%)
• no calcifications
• concurrent cervical lymphadenopathy (80%)