Anaplastic thyroid cancer staging refers to TNM staging of anaplastic thyroid carcinomas. Papillary, follicular, and medullary thyroid carcinomas are staged separately. The following article reflects the 8^th version manual published by the American Joint Committee on Cancer, which is used for staging starting January 1, 2018 ^1,2.

Primary tumor (T)

• 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, limited to the thyroid

  • T1b: tumor >1 cm but ≤2 cm, limited to the thyroid

• T2: tumor >2 cm but ≤4 cm, 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)

• T4: gross extrathyroidal extension beyond the strap muscles

  • T4a: tumor invading subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve

  • T4b: tumor invading prevertebral fascia or encasing carotid artery or mediastinal vessels

Regional lymph node (N)

• NX: regional lymph nodes cannot be assessed

• N0: no regional lymph node metastasis

  • N0a: one or more lymph nodes confirmed benign by cytology/histology

  • N0b: no radiologic or clinical evidence of regional lymph node metastasis

• N1: regional lymph node metastasis

  • N1a: central lymph node metastases to level VI (pretracheal, paratracheal, and prelaryngeal/Delphian lymph nodes) or level VII (upper mediastinal); can be unilateral or bilateral

  • N1b: lateral neck lymph node metastases (levels I, II, III, IV, or V, or retropharyngeal); can be unilateral, bilateral, or contralateral

Distant metastases (M)

The terms pM0 and MX are not valid TNM categories. The following categories may be used:

• cM0: no evidence of metastases

• cM1: distant metastasis

• pM1: distant metastasis, microscopically confirmed

Stage groups

• stage IVA

  • [T1, T2, T3a], [N0, NX], M0

• stage IVB

  • [T1, T2, T3a], N1, M0

  • [T3b, T4], [Any N], M0

• stage IVC

  • [Any T], [Any N], M1

Changes since prior versions

Compared to the 7^th edition, anaplastic tumors are no longer automatically classified as T4 disease and T category is defined the same as for differentiated thyroid cancers. The stage groups were modified accordingly to reflect the poor prognosis of anaplastic thyroid cancer: stage IVA indicates intrathyroidal disease, stage IVB indicates extrathyroidal extension or regional nodal metastases, and stage IVC indicates distant metastases.

See also

• differentiated thyroid cancer staging