Types and Stages of Thyroid Cancer

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The thyroid is a butterfly-shaped gland near the base of the throat. It has two sides, or lobes, with one on either side of the windpipe. Thyroid tumors or nodules are fairly common and about 90% of them are benign. Around 10% of them will turn out to be cancerous.

As part of a cancer diagnosis, doctors will stage the cancer. For thyroid cancer, the stage depends on the type of cancer. A person’s age also plays a role in staging certain kinds of thyroid cancer. Staging is a way of describing the extent of cancer in the body. This information helps doctors choose the best treatment and predict the likelihood of success.

There are four main stages for most kinds of thyroid cancer. Doctors use Roman numerals to label the stages: I, II, III and IV. Some stages also have letters to describe substages. Higher numbers represent more advanced cancers. Lower numbers are earlier stages, which generally have a better prognosis. However, even some advanced thyroid cancers remain highly treatable and have a positive outlook.

Biopsy and imaging exam results give doctors the information they need to stage cancers. The thyroid cancer stage depends on:

  • How large the tumor is and whether it extends outside the gland
  • Whether cancer cells have spread to your lymph nodes
  • Whether the cancer has metastasized—or spread—to other parts of the body

Papillary or Follicular Thyroid Cancer Under Age 55

Papillary and follicular cancers are the most common types of thyroid cancer. Together, they account for about 95% of thyroid cancers. Of the two, papillary cancer is more common. About 8 in 10 thyroid cancers are papillary. This cancer starts in the follicular cells—the cells that make thyroid hormone. It typically occurs in one lobe and is a differentiated cancer. This means it looks a lot like normal thyroid cells under a microscope. Papillary thyroid cancer often spreads to lymph nodes.

Follicular cancer also starts in the follicular cells, but is much less common. Only 1 in 10 thyroid cancers are follicular cancer. Like papillary cancer, it is a differentiated cancer. Both types tend to grow slowly. However, follicular cancer rarely spreads to lymph nodes. It is more likely to spread to other parts of the body.

People under age 55 are less likely to die from a differentiated thyroid cancer. Staging takes this into account by breaking out this age group. Stages of papillary or follicular cancer for people younger than 55 years are:

  • Stage I: This stage is a tumor of any size that may have spread to nearby lymph nodes or tissues, but not to distant sites in the body.
  • Stage II: This stage is a tumor of any size that has spread to another part of the body. It may or may not have spread to lymph nodes.

Surgery has an excellent cure rate for these cancers. People with stage II cancers may also receive radioactive iodine and other cancer treatments.

Papillary or Follicular Thyroid Cancer Age 55 and Older

The prognosis for people over the age of 55 is not quite as good as younger people. So, the staging is different for this age group. Stages of papillary or follicular cancer for people older than 55 years are:

  • Stage I: This stage is a tumor 4 cm or smaller with cancer only in the thyroid. It has not spread outside the thyroid or to lymph nodes.
  • Stage II: This stage is a tumor 4 cm or smaller that is still confined to the thyroid but cancer cells have spread to lymph nodes. OR it is a tumor larger than 4 cm that is still confined to the thyroid and it may or may not have spread to lymph nodes. OR it is a tumor of any size that has spread to nearby muscles but not to distant sites and it may or may not have spread to lymph nodes.
  • Stage III: This stage is a tumor of any size that has spread outside the thyroid to soft tissues, the voice box, the esophagus or the trachea. It may or may not have spread to lymph nodes, but has not spread to distant body sites.
  • Stage IVA: This stage is a tumor of any size that has spread extensively to nearby tissues in front of the spine or surrounding the carotid artery or blood vessels between the lungs. It may or may not have spread to lymph nodes, but has not spread to distant sites.
  • Stage IVB: This is a tumor of any size that has spread beyond nearby tissues to distant body sites, most commonly the lungs or bones.

When cancer has spread to distant sites, the prognosis is poorer than when it remains in the thyroid. At these later stages, treatment may involve external beam radiation therapy, targeted therapy, or chemotherapy.

Medullary Thyroid Cancer

Medullary thyroid cancer accounts for about 4% of thyroid cancers. It starts in the C cells. These cells make calcitonin, a hormone that regulates the use of calcium. This type of thyroid cancer has little resemblance to normal thyroid cells. It can be hard to find and may have already spread to lymph nodes and distant sites at diagnosis. This type of thyroid cancer can also be harder to treat.

About 25% of medullary thyroid cancers are inherited or familial. This means family members are at increased risk of developing it too. A genetic test is available for people with familial medullary thyroid cancer.

Stages of medullary thyroid cancer are:

  • Stage I: This stage is a small tumor of 2 cm or less with cancer only in the thyroid. There is no spread to lymph nodes and no metastasis.
  • Stage II: This stage is a tumor larger than 2 cm, but cancer is still only in the thyroid. OR the tumor is any size with spread to the muscles in the neck.
  • Stage III: This stage is a tumor of any size with spread to lymph nodes around the thyroid gland on one or both sides of the neck. The cancer may or may not have spread to the muscles in the neck, but has not spread to distant sites.
  • Stage IVA: This stage is a tumor of any size that has spread outside the thyroid to soft tissues, the voice box, the esophagus or the trachea. It may or may not have spread to lymph nodes on one or both sides of the neck. OR it is a tumor of any size with spread to lymph nodes throughout the neck on one or both sides or in the chest. The cancer may or may not have spread to the muscles in the neck, but has not spread to distant body sites.
  • Stage IVB: This is a tumor of any size that has spread extensively in the neck and upper chest. It may or may not have spread to lymph nodes.
  • Stage IVC: This is a tumor of any size that has spread to distant body sites, such as the lungs or liver.

Anaplastic Thyroid Cancer

Anaplastic thyroid cancer is rare, accounting for about 1% of thyroid cancers. It may develop from either papillary or follicular cancer or from a benign tumor. It is an undifferentiated cancer, meaning it bears very little similarity to normal thyroid cells.

This form of thyroid cancer is very fast-growing and spreads quickly. Usually, it has already spread within the neck by the time of diagnosis. Its aggressiveness makes it harder to treat successfully. Because of the poor treatment prognosis doctors consider all anaplastic thyroid cancer to be stage IV. The anaplastic thyroid cancer stages are:

  • Stage IVA: This stage is a tumor of any size with cancer only in the thyroid. It has not spread to lymph nodes or distant parts of the body.
  • Stage IVB: This stage is a tumor of any size. The tumor has not invaded tissues outside the thyroid, but there are cancer cells in lymph nodes. OR it is a tumor of any size that has spread to nearby muscles or more extensively into structures in the neck. It may or may not have spread to lymph nodes.
  • Stage IVC: This stage is a tumor of any size that has spread to distant parts of the body.

Planning Treatment

Your treatment options depend on the type of thyroid cancer and its stage. Your age and other factors play a role as well. Talk with your doctor about your options and your treatment goals. For thyroid cancers that are advanced or difficult to treat, consider asking about a clinical trial. Clinical trials can give you access to cutting-edge treatments that aren’t available to the public yet. Participating in a clinical trial also helps doctors understand how to improve future treatments.

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Apr 8
  1. Thyroid Cancer. American Society of Clinical Oncology. https://www.cancer.net/cancer-types/thyroid-cancer/introduction
  2. Thyroid Cancer Stages. American Cancer Society. https://www.cancer.org/cancer/thyroid-cancer/detection-diagnosis-staging/staging.html
  3. Thyroid Cancer Treatment (Adult) (PDQ®)–Patient Version. National Cancer Institute. https://www.cancer.gov/types/thyroid/patient/thyroid-treatment-pdq#_27
  4. Thyroid Cancer Treatment (Adult) (PDQ®)–Health Professional Version. National Cancer Institute. https://www.cancer.gov/types/thyroid/hp/thyroid-treatment-pdq#_139
  5. Treatment of Thyroid Cancer by Type and Stage. American Cancer Society. https://www.cancer.org/cancer/thyroid-cancer/treating/by-stage.html
  6. What Is Thyroid Cancer? American Cancer Society. https://www.cancer.org/cancer/thyroid-cancer/about/what-is-thyroid-cancer.html
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