Cancer that begins in the cells of the thyroid gland is classified as thyroid cancer. Your thyroid is made up of several different types of cells, and the type of cancer will depend on which cells are affected. Additionally, your treatment for thyroid cancer will depend on both the type of thyroid cancer you have, as well as the stage of the cancer.
Staging for thyroid cancer generally follows the TNM staging system. This is made up of classifications about the tumor (T), the lymph nodes (N), and whether the cancer has metastasized (M).
Tumor Categories
The “T” in TNM refers to the size of the primary tumor in the thyroid and whether or not it has grown into nearby areas. The staging for this category is split into the different types of thyroid cancer, including anaplastic thyroid cancer and non-anaplastic thyroid cancer.
Non-anaplastic thyroid tumors are gauged based on the size of the tumor measured in centimeters. This ranges from a tumor that is less than 2 centimeters across and has not grown out of the thyroid to a tumor that is larger than 4 centimeters and has grown extensively beyond the thyroid gland into the spine or nearby large blood vessels.
Anaplastic thyroid tumors are classified simply on whether or not the tumor has grown outside of the thyroid.
Lymph Node Categories
The “N” part of TNM staging is focused on the extent of spread to nearby lymph nodes. Thyroid cancer cells can potentially spread to the lymph nodes in the neck and chest areas. The stages for this category depend on if the cancer has spread to the lymph nodes, as well as which lymph nodes are being affected.
Metastasize Categories
The TNM staging system’s last portion, “M,” describes whether the cancer has spread (metastasized) to other organs in the body. Thyroid cancer will most often spread to the lungs, liver, and the bones.
Stage Categories
Once the values for TNM are decided based on extensive testing and diagnosis, the categories are combined into stages that are expressed using Roman numerals I through IV. Thyroid cancer staging is different than most other cancers, since it also considers the subtype of the thyroid cancer and the age of the patient at the time of diagnosis in order to determine a prognosis.
The stages are determined based on:
- Papillary or follicular thyroid cancer: This type of thyroid cancer is divided into two categories based on whether or not the patient is older than 45 years old.
- Medullary thyroid cancer: Age is not a factor in this type of cancer, as the prognosis will be the same no matter what your age.
- Anaplastic thyroid cancer: All anaplastic thyroid cancers will begin at stage IV, which is why this type of thyroid cancer usually receives a poor prognosis.
- Recurrent cancer: Your prognosis will suffer if your cancer returns after it has already been treated. A new stage will usually be assigned based on how far the cancer is spread, taking into consideration your original staging.
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