Thyroid gland
Miscellaneous
AJCC / TNM staging

Author: Andrey Bychkov, M.D., Ph.D.

Revised: 7 August 2018, last major update December 2017

Copyright: (c) 2003-2018, PathologyOutlines.com, Inc.

PubMed Search: TNM[TI] OR AJCC[TI] staging thyroid

Cite this page: Bychkov, A. AJCC / TNM staging. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/thyroidstaging.html. Accessed October 20th, 2018.

Pathologic TNM staging of differentiated and anaplastic thyroid cancer, AJCC 8th edition
Definition / general
  • AJCC / TNM staging is used for predicting disease specific survival
  • Clinical staging is based on inspection / palpation and imaging (ultrasound, PET / CT, etc.) of thyroid gland and regional lymph nodes
  • Pathologic staging (pTNM) is based on all information used for clinical staging plus histologic examination plus surgeon's description of gross unresected tumor
  • Any information obtained within the first 4 months after thyroid surgery should be used to refine the N and M status
  • AJCC 8th edition (Amin: AJCC Cancer Staging Manual, 8th Edition, 2017) is effective from January 1, 2018
  • Other staging systems also exist (Ann Surg 2007;245:366, Endocr Relat Cancer 2007;14:29)
Essential features
  • T, N and M categories are the mainstay for predicting survival in patients with thyroid cancer
  • Age (cutoff of 55 years) is an essential variable for AJCC staging of differentiated thyroid cancer
TNM definitions
Primary tumor (pT) for papillary, follicular, poorly differentiated, Hürthle cell and anaplastic thyroid carcinomas:
  • 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 into major neck structures
    • 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 carotid artery or mediastinal vessels from a tumor of any size

Primary tumor (pT) for medullary thyroid carcinomas:
  • TX - T3: Definitions are similar to the above
  • T4: Advanced disease
    • T4a: Moderately advanced disease; tumor of any size with gross extrathyroidal extension into the nearby tissues of the neck, including subcutaneous soft tissue, larynx, trachea, esophagus or recurrent laryngeal nerve
    • T4b: Very advanced disease; tumor of any size with extension toward the spine or into nearby large blood vessels, invading the prevertebral fascia or encasing the carotid artery or mediastinal vessels

Regional lymph node (pN):
  • NX: Regional lymph nodes cannot be assessed
  • N0: No evidence of regional lymph node metastasis
    • N0a*: One or more cytologic 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, 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):
  • M0: No distant metastasis
  • M1: Distant metastasis

* All categories may be subdivided: (s) solitary tumor and (m) multifocal tumor (the largest tumor determines the classification)
AJCC prognostic stage grouping
Differentiated thyroid cancer:
Age at diagnosis < 55 years
Stage I: any T any N M0
Stage II: any T any N M1
Age at diagnosis ≥ 55 years
Stage I: T1 N0 / NX M0
T2 N0 / NX M0
Stage II: T1 N1 M0
T2 N1 M0
T3a / T3b any N M0
Stage III: T4a any N M0
Stage IVA: T4b any N M0
Stage IVB: any T any N M1

Medullary thyroid cancer:
Stage I: T1 N0 M0
Stage II: T2 N0 M0
T3 N0 M0
Stage III: T1 - 3 N1a M0
Stage IVA: T4a any N M0
T1 - 3 N1b M0
Stage IVB: T4b any N M0
Stage IVC: any T any N M1

Anaplastic thyroid cancer:
Stage IVA: T1 - T3a N0 / NX M0
Stage IVB: T1 - T3a N1 M0
T3b any N M0
T4 any N M0
Stage IVC: any T any N M1
Major changes in the AJCC / TNM 8th edition
Differentiated thyroid cancer (Thyroid 2017;27:751):
  1. Age cutoff used for staging was increased from 45 to 55 years at diagnosis
  2. Minimal extrathyroidal extension detected only on histologic examination was removed from the definition of T3 disease and therefore has no impact on either T category or overall stage
  3. N1 disease no longer upstages a patient to stage III; if the patient's age is < 55 years at diagnosis, N1 disease is stage I; if age is ≥ 55 years, N1 disease is stage II
  4. T3a is a new category for tumors > 4 cm confined to the thyroid gland
  5. T3b is a new category for tumors of any size demonstrating gross extrathyroidal extension into strap muscles (sternohyoid, sternothyroid, thyrohyoid or omohyoid muscles)
  6. Level VII lymph nodes, previously classified as lateral neck lymph nodes (N1b), were reclassified as central neck lymph nodes (N1a) to be more anatomically consistent and because level VII presented significant coding difficulties for tumor registrars, clinicians and researchers
  7. In differentiated thyroid cancer, the presence of distant metastases in older patients is classified as stage IVB disease rather than stage IVC disease; distant metastasis in anaplastic thyroid cancer continues to be classified as stage IVC disease

Anaplastic thyroid cancer (CA Cancer J Clin 2018;68:55):
  1. Unlike previous editions where all anaplastic thyroid cancers were classified as T4 disease, anaplastic cancers will now use the same T definitions as differentiated thyroid cancer
  2. Intrathyroidal disease is stage IVA, gross extrathyroidal extension or cervical lymph node metastases are stage IVB and distant metastases are stage IVC
Diagrams / tables

Images hosted on PathOut server:

Images contributed by Dr. Andrey Bychkov:

AJCC / TNM charts



Images hosted on other servers:

Levels of the cervical lymph nodes



TNM sketches:

T category

N category

T1N0

T2N0


T3N0 and T1N1

T3N1

T1M1

T2M1

Videos

Staging thyroid cancer (2010) by MSKCC

Staging of medullary thyroid cancer (2013) by OncLiveTV

Staging animation

Board review question #1
50 year old woman presented with widely invasive follicular thyroid carcinoma penetrating thyroid capsule and strap muscles (confirmed on thyroidectomy) and spinal metastasis (confirmed by imaging and biopsy). What is the clinical stage as per the AJCC / TNM 8th edition?

  1. Stage I
  2. Stage II
  3. Stage III
  4. Stage IVA
  5. Stage IVC
Board review answer #1
B. Stage II. Despite the advanced disease, this patient is qualified as having stage II because her age is less than 55 years. Age at presentation is a critical prognostic characteristic in well differentiated thyroid carcinoma.
Board review question #2
Histopathological examination of total thyroidectomy specimen revealed conventional papillary thyroid carcinoma in the right lobe (1.8 cm), with minimal extrathyroidal extension (perithyroidal fat), microscopically involved posterior resection margin and micrometastasis in the single perithyroidal lymph node (0.2 cm). What are the correct pT and pN categories?

  1. pT1N0
  2. pT1aN1a
  3. pT1bN1a
  4. pT2N1a
  5. pT3N1a
Board review answer #2
C. pT1bN1a. T1b describes a tumor > 1 cm but ≤ 2 cm in greatest dimension limited to the thyroid. Minimal extrathyroidal extension was removed from the definition of T3 disease in the AJCC / TNM 8th edition and therefore has no impact on T category. Metastasis to the central lymph nodes qualifies as N1a.