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Thyroid cancer staging

Staging of thyroid malignancies is by the TNM staging system. This applies to papillary, follicular and medullary thyroid cancer. For anaplastic cancer, there is no generally accepted stating system. All patients with anaplastic thyroid cancer are considered to have stage IV disease.

T: Tumour
  • 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 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 in greatest dimension limited to the thyroid or any tumor with minimal extrathyroid extension (e.g., extension to sternothyroid muscle or perithyroid soft tissues)
  • T4 - Advanced disease
    • T4a - Moderately advanced disease - tumor of any size extending beyond the thyroid capsule to invade subcutaneous soft tissues, larynx, trachea, esophagus, or recurrent laryngeal nerve
    • T4b - Very advanced disease - tumor invades prevertebral fascia or encases carotid artery or mediastinal vessels
    • cT4a - Intrathyroidal anaplastic carcinoma
    • cT4b - Anaplastic carcinoma with gross extrathyroid extension
N: Nodes
  • NX - Regional lymph nodes cannot be assessed
  • N0 - No regional lymph node metastasis
  • N1 - Regional lymph node metastasis
    • N1a - Metastases to Level VI (pretracheal, paratracheal, and prelaryngeal/Delphian lymph nodes)
    • N1b - Metastases to unilateral, bilateral, or contralateral cervical (Levels I, II, III, IV, or V) or retropharyngeal or superior mediastinal lymph nodes (Level VII)
M: Metastases
  • MX – Distant metastases cannot be assessed
  • M0 - No distant metastasis
  • M1 - Distant metastasis

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