TNM staging system of thyroid carcinomas

TNM staging system

T categories for thyroid cancer (other than anaplastic thyroid cancer)

TX: Primary tumor cannot be assessed.

 T0: No evidence of primary tumor.
 T1: The tumor is 2 cm (slightly less than an inch) across or smaller and has not grown out of the thyroid.

• T1a: The tumor is 1 cm (less than half an inch) across or smaller and has not grown outside the thyroid.
• T1b: The tumor is larger than 1 cm but not larger than 2 cm across and has not grown outside of the thyroid.

 T2: The tumor is more than 2 cm but not larger than 4 cm (slightly less than 2 inches) across and has not grown out of the thyroid.

 T3: The tumor is larger than 4 cm across, or it has just begun to grow into nearby tissues outside the thyroid.

 T4: Tumor largely outside the thyroid

• T4a: The tumor is any size and has grown extensively beyond the thyroid gland into nearby tissues of the neck, such as the larynx (voice box), trachea (windpipe), esophagus (tube connecting the throat to the stomach), or the nerve to the larynx. This is also called moderately advanced disease.
• T4b: The tumor is any size and has grown either back toward the spine or into nearby large blood vessels. This is also called very advanced disease.

T categories for anaplastic thyroid cancer: All anaplastic thyroid cancers are considered T4 tumors at the time of diagnosis.

 T4a: The tumor is still within the thyroid.
 T4b: The tumor has grown outside the thyroid.
N categories for thyroid cancer

NX: Regional (nearby) lymph nodes cannot be assessed.

N0: The cancer has not spread to nearby lymph nodes.

N1: The cancer has spread to nearby lymph nodes.

N1a: The cancer has spread to lymph nodes around the thyroid in the neck (called pretracheal, paratracheal, and prelaryngeal lymph nodes).
N1b: The cancer has spread to other lymph nodes in the neck (called cervical) or to lymph nodes behind the throat (retropharyngeal) or in the upper chest (superior mediastinal).

M categories for thyroid cancer

M0: There is no distant metastasis.

M1: The cancer has spread to other parts of the body, such as distant lymph nodes, internal organs, bones, etc.

References