Staging is the process of finding out if and how far a cancer has spread. The stage of a cancer is one of the most important factors in choosing treatment options and predicting your chance for cure and long-term survival.

Staging is based on the results of the physical exam, biopsy, and imaging tests (ultrasound, CT scan, MRI, chest x-ray, and/or nuclear medicine scans), which are described in the section, "How Is Thyroid Cancer Diagnosed?"

The TNM staging system

A staging system is a standard way for the cancer care team to summarize how large a cancer is and how far it has spread. Ask your doctor to explain thyroid cancer staging in a way that you understand so that you can take a more active role in making informed decisions about your treatment.

The most common system used to describe the stages of cancers is the American Joint Committee on Cancer (AJCC) TNM system. The TNM system describes 3 key pieces of information:

• T indicates the size of the main (primary) tumor and whether it has grown into nearby areas.

• N describes the extent of spread to nearby (regional) lymph nodes. Lymph nodes are small bean-shaped collections of immune system cells that are important in fighting infections. Cells from oral cavity or oropharyngeal cancers can travel to lymph nodes in the neck area.

• M indicates whether the cancer has spread (metastasized) to other organs of the body. (The most common site of spread of thyroid cancer is to the lungs. The next most common sites are the liver and bones.)

Numbers or letters appear after T, N, and M to provide more details about each of these factors. The numbers 0 through 4 indicate increasing severity. The letter X means "cannot be assessed because the information is not available."

T categories for thyroid cancer:

T categories for anaplastic thyroid cancers:

N categories for thyroid cancer:

M categories for thyroid cancer:

Stage grouping

To make this information clearer, TNM descriptions can be grouped together into stage I through stage IV. Unlike most other cancers, thyroid cancers are grouped into stages in a way that considers both the subtype of cancer and the patient's age.

For papillary or follicular thyroid carcinoma (differentiated thyroid cancer)

Younger people have a low likelihood of dying from differentiated (papillary or follicular) thyroid cancer. The TNM stage groupings for these cancers take this fact into account. So, all people younger than 45 years with papillary thyroid cancer, for example, are stage I if they have no distant spread and stage II if they have distant metastases beyond the neck or upper mediastinal lymph nodes.

Patients younger than 45 years:

Stage I (any T, any N, M0): The tumor can be any size and may or may not have spread to nearby lymph nodes. It has not spread to distant sites.

Stage II (any T, any N, M1): The tumor can be any size and may or may not have spread to nearby lymph nodes. It has spread to distant sites.

Patients 45 years and older:

Stage I (T1, N0, M0): The tumor is less than 2 cm across and has not spread to nearby lymph nodes or distant sites.

Stage II (T2, N0, M0): The tumor is 2 to 4 cm across and has not spread to nearby lymph nodes or distant sites.

Stage III (T3, N0, M0 or T1 to T3, N1a, M0): One of the following applies:

• The tumor is larger than 4 cm or has grown slightly outside the thyroid, but it has not spread to nearby lymph nodes or distant sites.

• The tumor is any size and has spread to lymph nodes around the thyroid in the neck (cervical nodes) but not to distant sites.

Stage IVA (T4a, N0 to N1a, M0 or T1 to T4, N1b, M0): One of the following applies:

• The tumor is any size and has grown beyond the thyroid gland to invade nearby tissues of the neck. It may or may not have spread to lymph nodes around the thyroid in the neck (cervical nodes). It has not spread to distant sites.

• The tumor is any size and may have grown outside the thyroid gland. It has spread to lymph nodes in the side of the neck (lateral cervical nodes) or upper chest (upper mediastinal nodes) but not to distant sites.

Stage IVB (T4b, any N, M0): The tumor is any size and has grown either back to the spine or into nearby large blood vessels. It may or may not have spread to nearby lymph nodes, but it has not spread to distant sites.

Stage IVC (any T, any N, M1): The tumor is any size and may or may not have grown outside the thyroid. It may or may not have spread to nearby lymph nodes. It has spread to distant sites.

For medullary thyroid carcinoma

Stage grouping for medullary thyroid carcinoma in people of any age is the same as for papillary or follicular carcinoma in people older than age 45.

For anaplastic/undifferentiated thyroid carcinoma

All anaplastic thyroid cancers are considered stage IV, reflecting the poor prognosis of this type of cancer.

Stage IVA (T4a, any N, M0): The tumor is still within the thyroid and may be resectable (removable by surgery). It may or may not have spread to nearby lymph nodes, but it has not spread to distant sites.

Stage IVB (T4b, any N, M0): The tumor has grown outside the thyroid and is not resectable. It may or may not have spread to nearby lymph nodes, but it has not spread to distant sites.

Stage IVC (any T, any N, M1): The tumor is any size and may or may not have grown outside of the thyroid. It may or may not have spread to nearby lymph nodes. It has spread to distant sites.

Recurrent (relapsed) cancer

This is not an actual stage in the TNM system. Recurrent (relapsed) disease means that the cancer has come back (recurred) after treatment. Thyroid cancer usually returns in the neck, but it may reappear in another part of the body (for example, lymph nodes, lungs, or bones). Doctors may assign a new stage based on how far the cancer has spread, but this is not usually as formal a process as the original staging. The presence of recurrent disease does not change the original, formal staging.

If you have any questions about the stage of your cancer or how it affects your treatment, do not hesitate to ask your doctor.

Thyroid cancer survival by type and stage

The following survival statistics come from the AJCC Cancer Staging Manual (6th Ed). There are some important points to note about these numbers:

• The 5-year survival rate refers to the percentage of patients who live at least 5 years after being diagnosed. Many of these patients live much longer than 5 years after diagnosis. Five-year relative survival rates (such as the numbers below) don't include patients who die from other causes. They are considered to be a more accurate way to describe the outlook for patients with a particular type and stage of cancer.

• These numbers were derived from patients treated between 1985 and 1991. Although they are among the most current numbers we have available, they represent people who were first diagnosed and treated at least 15 to 20 years ago. Improvements in treatment since then mean that the outlook for people now being diagnosed with these cancers is likely to be better.

• Survival statistics can sometimes be useful as a general guide, but they may not accurately represent any one person's prognosis. A number of other factors, including other tumor characteristics and a person's age and general health, can also affect outlook. Your doctor is likely to be a good source as to whether these numbers may apply to you, as he or she is familiar with the aspects of your particular situation.

Papillary thyroid cancer

Follicular thyroid cancer

Note: All the stage III and IV patients with follicular or papillary thyroid cancer are, by definition, over 45 years old.

Medullary thyroid cancer

Anaplastic

The 5-year relative survival rate for anaplastic (undifferentiated) carcinomas, all of which are considered stage IV, is around 9%.

Last Medical Review: 04/28/2009
Last Revised: 05/14/2009