Thyroid (Anaplastic)

Anaplastic thyroid carcinoma now uses the same T/N/M categorization system as differentiated thyroid carcinoma.
Previously all anaplastic thyroid carcinoma was considered to be T4 at diagnosis.

T Category	Criteria
T0	No evidence of primary tumour
TX	Primary tumour cannot be assessed
T1	2 cm or smaller and limited to the thyroid.
T1a	1 cm or less and limited to the thyroid.
T1b	> 1 - 2 cm and limited to the thyroid.
T2	>2 - 4 cm and limited to the thyroid.
T3	>4 cm and limited to the thyroid OR any size with gross extrathyroidal extension to the straps only.
T3a	>4 cm and limited to the thyroid
T3b	Primary tumour of any size with gross extrathyroidal extension to the straps only.
T4	Gross extrathyroidal extension beyond the strap muscles.
T4a	Gross extrathyroidal extension to the trachea, esophagus, soft tissues of the neck, larynx, or recurrent laryngeal nerve.
T4b	Gross extrathyroidal extension invading the pre-vertebral fascia, carotid artery encasement, or mediastinal vessels.

N Category	Criteria
NX	Regional lymph nodes cannot be assessed.
N0	No evidence of locoregional lymph node metastasis.
N0a	One or more cytologically or histologically confirmed benign lymph nodes.
N0b	No radiologic or clinical evidence of lymph node metastasis.
N1	Metastasis to regional nodes.
N1a	Metastasis to level VI or level VII (central compartment lymph nodes)
N1b	Metastasis to lateral neck nodes (I-V) or retropharyngeal lymph nodes.

M Category	Criteria
M0	No distant metastasis
M1	Distant metastasis present