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Topic Overview

After you are diagnosed with thyroid cancer, you will have tests to determine the type of cancer cells you have and whether cancer has spread (metastasized) to other parts of your body.

Staging for thyroid cancer is based on the size of the cancer, lymph node involvement, and the involvement of underlying structures, such as muscle or bone. Staging of thyroid cancer has been classified by the American Joint Committee on Cancer (AJCC).¹

• TX: Primary tumor cannot be assessed.
• T0: No evidence of primary tumor.
• T1: Tumor is 2 cm (0.8 in.) or smaller and limited to the thyroid.
• T1a: Tumor is 1 cm (0 in.) or smaller and limited to the thyroid.
• T1b: Tumor is larger than 1 cm (0 in.) but not larger than 2 cm (1 in.) and limited to the thyroid.
• T2: Tumor is larger than 2 cm (0.8 in.) but not larger than 4 cm (2 in.) and limited to the thyroid.
• T3: Tumor is larger than 4 cm (2 in.) and limited to the thyroid or a tumor of any size that has spread just outside the thyroid.
• T4a: Moderately advanced disease. Tumor of any size extending beyond the thyroid to involve soft tissues beneath the skin, the larynx, trachea, esophagus, or recurrent laryngeal nerve.
• T4b: Very advanced disease. Tumor extends into the prevertebral fascia or around the carotid artery or mediastinal vessels.

All anaplastic cancers are considered T4 tumors:

• T4a: Intrathyroidal anaplastic cancer.
• T4b: Anaplastic cancer that has gross extrathyroid extension.

After the tumor (T) is staged, the TNM system stages lymph node involvement (N) to help determine the treatment options at each stage. The nearby (regional) lymph nodes are the central compartment, the lateral cervical, and the upper mediastinal lymph nodes. Lymph node involvement is staged in the following way:

• NX: Nearby lymph nodes cannot be assessed.
• N0: Cancer has not spread (metastasized) to the nearby lymph nodes.
• N1: Cancer has spread to nearby lymph nodes.
• N1a: Cancer has spread to Level VI, which includes the pretracheal, paratracheal, and prelaryngeal/Delphian lymph nodes.
• N1b: Cancer has spread to the lymph nodes on one side, both sides, or opposite sides of the cervical (Levels I, II, III, IV, or V) or retropharyngeal or superior mediastinal lymph nodes (Level VII).

The last part is to determine whether cancer has spread to other parts of the body (metastasized). The TNM system stages metastasis (M) in the following way:

• M0: Cancer has not metastasized.
• M1: Cancer has metastasized.

The TNM staging system allows your doctor to recommend the most effective treatment options and discuss your long-term outcome (prognosis) based on the type of tumor, the stage of the cancer, your age, and your overall health.

The stage groupings are separate for papillary or follicular cancer, medullary cancer, and anaplastic cancer.