Thyroid & parathyroid
Thyroid - general
AJCC / TNM Staging
Author: Andrey Bychkov, M.D., Ph.D.
Last author update: 1 December 2017
Last staff update: 15 August 2023
Copyright: 2003-2024, PathologyOutlines.com, Inc.
PubMed Search: TNM[TI] OR AJCC[TI] staging thyroid
Table of Contents
Definition / general | Essential features | TNM definitions | AJCC prognostic stage grouping | Major changes in the AJCC / TNM 8th edition | Diagrams / tables | Videos | Board review style question #1 | Board review style answer #1 | Board review style question #2 | Board review style answer #2 | Additional referencesCite this page: Bychkov A. AJCC / TNM Staging. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/thyroidstaging.html. Accessed April 25th, 2024.
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:
Primary tumor (pT) for medullary thyroid carcinomas:
Regional lymph node (pN):
Distant metastasis (M):
* All categories may be subdivided: (s) solitary tumor and (m) multifocal tumor (the largest tumor determines the classification)
- 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:
Medullary thyroid cancer:
Anaplastic 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):
Anaplastic thyroid cancer (CA Cancer J Clin 2018;68:55):
- Age cutoff used for staging was increased from 45 to 55 years at diagnosis
- 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
- 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
- T3a is a new category for tumors > 4 cm confined to the thyroid gland
- T3b is a new category for tumors of any size demonstrating gross extrathyroidal extension into strap muscles (sternohyoid, sternothyroid, thyrohyoid or omohyoid muscles)
- 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
- 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):
- 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
- Intrathyroidal disease is stage IVA, gross extrathyroidal extension or cervical lymph node metastases are stage IVB and distant metastases are stage IVC
Diagrams / tables
Scroll to see all images:
Contributed by Andrey Bychkov, M.D., Ph.D.
AJCC / TNM charts
Images hosted on other servers:
Levels of the cervical lymph nodes
TNM sketches
T1N0
T2N0
T3N0 and T1N1
T3N1
T1M1
T2M1
Staging charts
Stage I, < 55 yo
Stage I, 55 yo
Stage II, < 55 yo
Stage II, > 55 yo
Stage III
Stage IVA
Stage IVB
Anaplastic cancer, stage IVA
Anaplastic cancer, stage IVB
Anaplastic cancer, stage IVC
Medullary cancer, stage I
Medullary cancer, stage II
Medullary cancer, stage III
Medullary cancer, stage IVA
Medullary cancer, stage IVB
Medullary cancer, stage IVC
Videos
Advanced thyroid carcinoma
Thyroid carcinoma
Staging thyroid cancer
Staging of medullary thyroid cancer
Staging animation
Board review style 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?
- Stage I
- Stage II
- Stage III
- Stage IVA
- Stage IVC
Board review style 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.
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Reference: Thyroid & parathyroid - Staging
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Reference: Thyroid & parathyroid - Staging
Board review style 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?
- pT1N0
- pT1aN1a
- pT1bN1a
- pT2N1a
- pT3N1a
Board review style 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.
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Reference: Thyroid & parathyroid - Staging
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Reference: Thyroid & parathyroid - Staging
Additional references
