The staging of thyroid cancer follows the same internationally accepted staging system of T (for primary tumor lesions), N (for lymph node metastases), and M (for distant metastases) (below), which classifies tumors into stages I-IV, with the later the stage, the worse the patient’s outcome.
The specific staging of medullary thyroid cancer is as follows:
| Staging | Meaning |
| I Period |
No lymph node metastasis or distant metastasis; The primary focus is confined to the thyroid gland and has a maximum diameter of ≤ 2 cm |
| Stage II | No lymph node metastases and no distant metastases Primary foci confined to the thyroid with a maximum diameter of >2 cm, or primary foci invading outside the thyroid but involving only the peripheral strap muscles (a group of muscles in the anterior neck band) |
| Stage III |
No distant metastases; Metastasis to zone VI or VII lymph nodes in the neck (below), or retropharyngeal lymph nodes; The primary focus was confined to the thyroid gland, or the primary focus invaded outside the thyroid gland but involved only the surrounding strap muscles |
| Stage IVA |
No distant metastases, with the primary focus confined to the thyroid but with metastases in the lymph nodes of the lateral cervical region (regions II-V) (below); or no distant metastasis, with or without lymph node metastasis, and involvement of the surrounding subcutaneous soft tissue, trachea, esophagus, or laryngeal nerve |
| Stage IVB | No distant metastases, with or without lymph node metastases, primary foci involving the spine or surrounding great vessels, invasion to the prevertebral fascia, encircling carotid artery or mediastinal vessels |
| Stage IVC | Distant metastases, regardless of the extent of the primary site and the presence or absence of lymph node metastases |
Figure Note: Internationally, cervical lymph nodes are divided into 7 zones, identified by Roman numerals I-VII. The lymph nodes in zones VI-VII are the central zone lymph nodes, and zones I-V are the lateral cervical zone lymph nodes. The most common lymph node metastasis in thyroid cancer is in the central zone, followed by the lateral cervical zone, and metastasis in zones II-V is common.
Co-written by Dr. Ben Ma, Cancer Hospital of Fudan University