What is the typical metastatic pattern for Medullary Thyroid Cancer (MTC)?

Metastatic Pattern for Medullary Thyroid Cancer

Medullary thyroid cancer metastasizes early to cervical lymph nodes (both paratracheal and lateral), and distant metastases most commonly affect the lungs, liver, and bones, with less frequent involvement of brain, skin, and breast. 1, 2

Regional Lymph Node Metastasis

• Cervical lymph node involvement occurs in approximately 50% of patients at initial presentation 1
• The tumor metastasizes early to both paratracheal (central/level VI) and lateral cervical lymph nodes (levels II-V) 3
• Mediastinal lymph nodes can also be involved as part of regional spread 4

Distant Metastatic Sites

Most Common Sites (in order of frequency):

1. Lungs - Most frequent site of distant metastasis 1, 2, 3
2. Liver - Second most common distant site 1, 2, 3
3. Bones - Third most common distant site 1, 2, 3

Less Common Sites:

• Brain - Rare but documented 1, 2, 3
• Skin - Rare 1, 2, 3
• Breast - Rare 1, 2
• Choroidal/ocular - Extremely rare presentation 5
• Pituitary - Extremely rare 5

Clinical Patterns and Timing

• Distant metastases are present initially in approximately 50% of cases 1
• Metastases are often multiple within affected organs and frequently involve multiple organs simultaneously 1
• Distant metastases occur predominantly in patients presenting with large-sized tumors, extrathyroidal growth, and lymph node involvement 1

Prognostic Implications

• Distant metastases are the main cause of death in MTC patients 1
• Survival after discovery of distant metastases: 51% at 1 year, 26% at 5 years, and 10% at 10 years 1
• Long survival has been observed in some patients with metastatic disease, particularly when metastases are discovered at an early stage 1

Detection Thresholds

• Imaging techniques typically will not demonstrate disease until serum calcitonin approaches levels >150 pg/mL 1, 3
• For calcitonin levels >150 pg/mL, the risk of metastases outside the neck is significantly higher, mandating comprehensive imaging including neck and chest CT, and liver evaluation 1