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.
T describes the size of the tumour. There are 4 main T stages for thyroid cancer, except for anaplastic thyroid cancer.
T1a – the tumour is entirely inside the thyroid and is less than 1cm across in any direction
T1b – the tumour is entirely inside the thyroid and is more than 1 cm but no more than 2cm across in any direction
T2 – the tumour is entirely inside the thyroid and is more than 2cm but no more than 4cm across in any direction.
T3a – the tumour is less than 4cm across and is only in the thyroid
For medullary thyroid cancer, T3a means that the tumour is 4cm or more across and is only in the thyroid.
T3b – the tumour is any size and it has spread to the one or more of the muscles beside the thyroid (strap muscles).
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.
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.
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 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 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).
N1b means the cancer has spread to other lymph nodes in the neck (called cervical nodes) or to lymph nodes behind the throat (retropharyngeal).
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).