TNM staging for thyroid cancer

The stage of a cancer tells you about its size and whether it has spread. It helps your doctor to decide which treatment you need.

Doctors use the TNM system to stage thyroid cancer. TNM stands for:

• tumour (cancer)
• node or lymph node
• metastasis

When a cancer spreads, this spread is called a metastasis or secondary.

Your doctor works out your TNM stage by looking at tissue from your thyroid and the results of your scans. It might not be possible to fully stage your cancer until after your surgery.

Doctors may also use another system called the number staging system. This system divides cancers into 4 groups, from stage 1 to stage 4.

Tumour (T)

T describes the size of the cancer. 

T0 means there is no sign of a cancer.

T1 means the cancer is within the thyroid gland and is 2cm or less. T1 tumours are further divided into T1a and T1b.

T1a

T1a means the cancer is completely inside the thyroid. It is1cm across or smaller.

T1b

T1b means the cancer is completely inside the thyroid. It is between 1cm and 2cm across.

T2

T2 means the cancer is completely inside the thyroid. It is more than 2cm but no greater than 4cm across.

T3

T3 is divided into T3a and T3b.

T3a

T3a means the cancer is more than 4cm across. It is still completely inside the thyroid.

T3b

T3b means the cancer is any size. It has grown outside the thyroid into one or more of the muscles beside the thyroid (strap muscles).

T4

T4 cancers have grown outside the thyroid and are divided into T4a and T4b.

T4a

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

T4b

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

Node (N)

N describes whether the cancer has spread to the lymph nodes. 

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

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

N1a

N1a means the cancer has spread to lymph nodes close to the thyroid in the neck. These are called the pretracheal, paratracheal, and prelaryngeal lymph nodes. Or it has spread to lymph nodes in the upper chest. These are the superior mediastinal lymph nodes. 

N1b

N1b means the cancer has spread to other lymph nodes in the neck. These are called cervical lymph nodes. Or it has spread to lymph nodes behind the throat, called the retropharyngeal lymph nodes.

Metastases (M)

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

M0 means the cancer hasn’t spread to another part of the body.

M1 means the cancer has spread to another part of the body, such as the lungs or bones.