Anaplastic thyroid cancer (staging)

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 edition manual published by the American Joint Committee on Cancer, which is used for staging starting January 1, 2018 .

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 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