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TNM staging

The stage of a cancer means how big it is and whether it has spread. it helps your doctor to decide which treatment you need.

It might not be possible to fully stage your cancer until after your surgery.

Doctors may also use a number staging system.

Tumour (T)

T describes the size of the tumour. There are 4 main T stages for thyroid cancer, except for anaplastic thyroid cancer.

T1a

T1a – the tumour is entirely inside the thyroid and is less than 1cm across in any direction

Diagram showing stage T1a thyroid cancer

T1b

T1b – the tumour is entirely inside the thyroid and is more than 1 cm but no more than 2cm across in any direction

Diagram showing stage T1b thyroid cancer

T2

T2 – the tumour is entirely inside the thyroid and is more than 2cm but no more than 4cm across in any direction.

Diagram showing stage T2 thyroid cancer

T3a

T3a – the tumour is less than 4cm across and is only in the thyroid

Diagram showing stage T3 thyroid cancer smaller than 4cm

For medullary thyroid cancer, T3a means that the tumour is 4cm or more across and is only in the thyroid.

T3b

T3b – the tumour is any size and it has spread to the one or more of the muscles beside the thyroid (strap muscles).

 

T4a

T4a – the cancer has grown outside the covering of the thyroid gland into nearby soft tissue, such as the voice box (larynx), windpipe (trachea), food pipe (oesophagus) or the voice box nerve (recurrent laryngeal nerve).

T4a thyroid cancer is called moderately advanced thyroid cancer.

Diagram showing stage T4a thyroid cancer

T4b

T4b – the cancer has grown outside the thyroid gland into the area surrounding the bones of the spine, or one of the main blood vessels in the neck area.

T4b thyroid cancer is called very advanced thyroid cancer.

Diagram showing stage T4b thyroid cancer

Anaplastic thyroid cancers

All anaplastic thyroid cancers are considered to be T4 tumours at the time of diagnosis.

  • T4a means that the tumour is still within the thyroid gland
  • T4b means that the tumour has spread outside the thyroid

Node (N)

Node describes whether your cancer has spread to the lymph nodes. There are 2 possible stages of lymph node involvement.

N0 means that the cancer hasn't spread to nearby lymph nodes.

N1 means the cancer has spread to nearby lymph nodes and is divided into 2 groups.

N1a

N1a means the cancer has spread to lymph nodes close to the thyroid in the neck (called pretracheal, paratracheal, and prelaryngeal lymph nodes) or in the upper chest (the superior mediastinal nodes). 

Diagram showing stage N1a thyroid cancer

N1b

N1b means the cancer has spread to other lymph nodes in the neck (called cervical nodes) or to lymph nodes behind the throat (retropharyngeal).

Diagram showing stage N1b thyroid cancer

Metastases (M)

Metastases (M) describes whether the cancer has spread to a different part of the body.

There are 2 possible stages of cancer spread. Either the cancer hasn't spread to another part of the body (M0) or it has spread (M1).

Diagram showing stage M1 thyroid cancer
Last reviewed: 
15 May 2018
  • AJCC Cancer Staging Manual (8th Edition)
    S Edge and others
    Springer, 2017
     

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