The stage of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the particular type and the stage of the thyroid cancer helps the doctors to decide on the most appropriate treatment.

Generally cancers are divided into four stages: small and localised (stage one); spread into surrounding structures (stages two or three); or spread into other parts of the body (stage four). If the cancer has spread to distant parts of the body this is known as secondary cancer (or metastatic cancer). Thyroid cancer is also staged according to the different types and the age of the person. The different staging systems are described below.

• Stage 1  The tumour can be of any size and nearby lymph nodes may also be affected, but there is no spread of the cancer to other parts of the body.

• Stage 2  A tumour of any size that has spread to other parts of the body, such as the bones or lungs.

There is no stage 3 or 4 for these patients.

• Stage 1  The tumour is no bigger than 2cm in size and is contained within the thyroid gland. There has been no spread to either the lymph nodes or other parts of the body.

• Stage 2  The tumour is contained within the thyroid gland and is between 2 and 4cm in size. There has still been no spread of the cancer to lymph nodes or other parts of the body.

• Stage 3  The tumour is bigger than 4cm in size and is contained within the thyroid gland. Or, the tumour is of any size and has spread just outside the gland or to nearby lymph nodes in the neck.

• Stage 4A  The tumour may be any size and has spread into surrounding parts of the neck (such as the muscles, nerves or blood vessels) and/or to lymph nodes in the neck or the upper chest.

• Stage 4B  The tumour may be of any size and has spread to neck tissues near the backbone or around the upper neck or chest. The cancer may also have spread to lymph nodes.

• Stage 4C  The cancer has spread to other parts of the body, such as the lung or bone.

Everyone with anaplastic thyroid cancer is considered to have stage 4 disease. This stage is divided into three, depending upon how far the cancer has spread.

• Stage 4A  The tumour is of any size and contained within the thyroid gland. Lymph nodes may also be affected, but the cancer has not spread to other parts of the body.

• Stage 4B  The tumour is of any size and it has begun to spread into the soft tissues of the neck. Lymph nodes may also be affected, but the cancer has not spread to other parts of the body.

• Stage 4C  The cancer has spread to other parts of the body, such as the lung or bones.

Your doctors may also describe your thyroid cancer using the TNM staging system.

T describes the size of the tumour. There are four main stages ranging from T1 – T4.

N describes whether the cancer has spread to the lymph nodes close to the thyroid gland. There are two stages: in N0 there is no sign of cancer in the lymph glands; in N1 there are cancer cells in the lymph glands.

M describes whether the cancer has spread to another part of the body, such as the lungs or the bones (secondary or metastatic cancer). There are two stages: M0 is where there are no metastases; M1 is where there are metastases.