Primary tumor (T) |
Papillary, follicular, poorly differentiated, Hürthle cell and anaplastic thyroid carcinoma |
T category | T criteria |
TX | Primary tumor cannot be assessed |
T0 | No evidence of primary tumor |
T1 | Tumor ≤2 cm in greatest dimension limited to the thyroid |
T1a | Tumor ≤1 cm in greatest dimension limited to the thyroid |
T1b | Tumor >1 cm but ≤2 cm in greatest dimension limited to the thyroid |
T2 | Tumor >2 cm but ≤4 cm in greatest dimension limited to the thyroid |
T3 | Tumor >4 cm limited to the thyroid, or gross extrathyroidal extension invading only strap muscles |
T3a | Tumor >4 cm limited to the thyroid |
T3b | Gross extrathyroidal extension invading only strap muscles (sternohyoid, sternothyroid, thyrohyoid, or omohyoid muscles) from a tumor of any size |
T4 | Includes gross extrathyroidal extension beyond the strap muscles |
T4a | Gross extrathyroidal extension invading subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve from a tumor of any size |
T4b | Gross extrathyroidal extension invading prevertebral fascia or encasing the carotid artery or mediastinal vessels from a tumor of any size |
NOTE: All categories may be subdivided: (s) solitary tumor and (m) multifocal tumor (the largest tumor determines the classification). |
Regional lymph nodes (N) |
N category | N 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 locoregional lymph node metastasis |
N1 | Metastasis to regional nodes |
N1a | Metastasis to level VI or VII (pretracheal, paratracheal, or prelaryngeal/Delphian, or upper mediastinal) lymph nodes. This can be unilateral or bilateral disease. |
N1b | Metastasis to unilateral, bilateral, or contralateral lateral neck lymph nodes (levels I, II, III, IV, or V) or retropharyngeal lymph nodes |
Distant metastasis (M) |
M category | M criteria |
M0 | No distant metastasis |
M1 | Distant metastasis |
Prognostic stage groups |
Differentiated |
When age at diagnosis is... | And T is... | And N is... | And M is... | Then the stage group is... |
<55 years | Any T | Any N | M0 | I |
<55 years | Any T | Any N | M1 | II |
≥55 years | T1 | N0/NX | M0 | I |
≥55 years | T1 | N1 | M0 | II |
≥55 years | T2 | N0/NX | M0 | I |
≥55 years | T2 | N1 | M0 | II |
≥55 years | T3a/T3b | Any N | M0 | II |
≥55 years | T4a | Any N | M0 | III |
≥55 years | T4b | Any N | M0 | IVA |
≥55 years | Any T | Any N | M1 | IVB |
Anaplastic |
When T is... | And N is... | And M is... | Then the stage group is... |
T1-T3a | N0/NX | M0 | IVA |
T1-T3a | N1 | M0 | IVB |
T3b | Any N | M0 | IVB |
T4 | Any N | M0 | IVB |
Any T | Any N | M1 | IVC |