Staging is a way of describing a cancer, such as where it is located, if or where it has spread, and if it is affecting the functions of other organs in the body. Doctors use diagnostic tests to determine the cancer’s stage, so staging may not be complete until all of the tests are finished. Knowing the stage helps the doctor to decide what kind of treatment is best and can help predict a patient's prognosis (chance of recovery). There are different stage descriptions for different types of cancer.
One tool that doctors use to describe the stage is the TNM system. This system uses three criteria to judge the stage of the cancer: the tumor itself, the lymph nodes around the tumor, and if the tumor has spread to other parts of the body. The results are combined to determine the stage of cancer for each person. There are five stages: stage 0 (zero) and stages I through IV (one through four). The stage provides a common way of describing the cancer, so doctors can work together to plan the best treatments.
TNM is an abbreviation for tumor (T), node (N), and metastasis (M). Doctors look at these three factors to determine the stage of cancer:
- How large is the primary tumor and where is it located? (Tumor, T)
- Has the tumor spread to the lymph nodes? (Node, N)
- Has the cancer metastasized to other parts of the body? (Metastasis, M)
In addition to the TNM system, papillary and follicular thyroid cancers are also staged by the age of the patient.
Tumor. Using the TNM system, the letter “T” plus a letter or number (0 to 4) is used to describe the size and location of the tumor. Some stages are also divided into smaller groups that help describe the tumor in even more detail. When describing “T” in thyroid cancer, doctors may subdivide the general categories by adding the letter “a” to indicate a solitary (single) tumor or “b” to indicate multifocal (more than one) tumors. Specific tumor stage information is listed below.
TX: The primary tumor cannot be evaluated.
T0: There is no evidence of a tumor.
T1: The tumor is 1 centimeter (cm) or smaller at its greatest dimension and limited to the thyroid.
T2: The tumor is at least 1 cm, but it is not larger than 4 cm and is limited to the thyroid.
T3: The tumor is larger than 4 cm, but the tumor does not extend beyond the thyroid gland.
T4: The tumor is any size and has extended beyond the thyroid.
Node. The “N” in the TNM staging system stands for lymph nodes. There are many regional lymph nodes located in the head and neck area, and careful assessment of lymph nodes is an important part of staging thyroid cancer. Lymph nodes in other parts of the body are called distant lymph nodes.
NX: The regional lymph nodes cannot be evaluated.
N0: There is no evidence of cancer in the regional lymph nodes.
N1: Cancer has spread to the lymph nodes.
N1a: Cancer has spread to the ipsilateral cervical lymph nodes (lymph nodes in the neck on the same side as the tumor).
N1b: Cancer has spread to the bilateral cervical (lymph nodes on both sides of the neck), the contralateral cervical (the opposite side of the tumor), the midline cervical (the middle of the neck), or the mediastinal (the chest) lymph nodes.
Distant metastasis. The “M” in the TNM system indicates whether cancer has spread to other parts of the body.
MX: Distant metastasis cannot be evaluated.
M0: Cancer has not spread to other parts of the body.
M1: Cancer has spread to other parts of the body.
Cancer stage grouping
Doctors assign the stage of the cancer by combining the T, N, and M classifications. For thyroid cancer, this staging system differs by tumor type. For papillary or follicular thyroid cancers, it also depends on the age of the patient.
Papillary or follicular thyroid tumors, in a person younger than 45
Stage I: This stage describes a tumor (any T) with no spread to lymph nodes (N0) and no distant metastasis (M0).
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Stage II: This stage describes a tumor (any T) with any metastasis (M1) regardless of whether it has spread to the lymph nodes (any N).
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Papillary or follicular thyroid tumors, in a person 45 and older
Stage I: This stage describes any small tumor (T1) with no spread to lymph nodes (N0) and no metastasis (M0).
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Stage II: This stage describes any larger, noninvasive tumor (T2, T3) with no spread to lymph nodes (N0) and no metastasis (M0).
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Stage III: This stage describes any invasive tumor (T4) with no spread to lymph nodes (N0) and no metastasis (M0), or any tumor (any T) with spread to lymph nodes (N1).
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Stage IV: This stage describes all tumors (any T, any N) when there is evidence of metastasis (M1).
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Medullary thyroid tumors
Stage I: This stage describes a small tumor (T1) with no spread to lymph nodes (N0) and no distant metastasis (M0).
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Stage II: This stage describes any tumor (any T) with no spread to lymph nodes (N0) and no metastasis (M0).
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Stage III: This stage describes any tumor (any T) that has spread to lymph nodes (N1) but has not metastasized (M0).
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Stage IV: This stage is used when there is evidence of metastasis (any T, any N, M1).
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Anaplastic thyroid tumors
Stage IV: All anaplastic thyroid tumors are classified as stage IV, regardless of tumor size, location, or metastasis.
Recurrent: Recurrent cancer is cancer that comes back after treatment.
Used with permission of the American Joint Committee on Cancer (AJCC), Chicago, Illinois. The original source for this material is the AJCC Cancer Staging Manual, Sixth Edition (2002) published by Springer-Verlag New York, www.cancerstaging.net
Last Updated: July 02, 2010
