What is Thyroid Cancer?

What is Thyroid Cancer?

Thyroid cancer is the uncontrolled growth of cells originating in the thyroid gland. The thyroid is a butterfly-shaped gland in the front of the neck, which produces hormones that help regulate your heart rate, metabolism, blood pressure, and body temperature.

Thyroid cancer diagram

Types of Thyroid Cancer


Different types of thyroid cancer depend on the cells from which they arise, and each requires its own treatment.

  • Papillary thyroid cancer - This form of the disease accounts for approximately 8 out of every 10 thyroid cancer cases. While it can affect people of any age, papillary thyroid cancer usually occurs in people aged 30 to 50. Most of these cancers are small and slow-growing, though they can spread to the lymph nodes in the neck.
  • Follicular thyroid cancer - The second most common type of thyroid cancer, follicular cancer, mostly affects people over age 50. Though this form of the disease rarely spreads to lymph nodes in the neck, large tumors of this type may spread to other parts of the body, including the bones and lungs.
  • Anaplastic thyroid cancer - A rare form of thyroid cancer that spreads quickly and is difficult to treat, anaplastic cancer sometimes develops out of existing papillary or follicular cancers. It usually occurs in people age 60 and up.
  • Medullary thyroid cancer - This rare form of thyroid cancer begins in the thyroid's C cells, which produce the hormone calcitonin. Treatment of this type of cancer typically requires removal of the entire thyroid and the lymph nodes around it. Medullary thyroid cancer can be a part of an inherited genetic syndrome.

Stages of Thyroid Cancer


When your doctor diagnoses you with thyroid cancer, they will use several key factors to determine the stage of the disease. Thyroid cancer staging can be complex and differs based on your cancer type, so it's important to discuss this topic with your doctor thoroughly. There are three significant questions doctors will consider when determining the stage—collectively referred to as the "TNM" system:

  • T: How big is the tumor? Has it grown out of the thyroid and into nearby organs or structures?
  • N: Has the cancer spread to the lymph nodes?
  • M: Has the cancer metastasized, or spread to distant organs?

Depending on how advanced each aspect of the TNM system is, your doctor will assign a number to each letter of the system. For example, a small tumor that has not grown outside the thyroid will be categorized as T1. A tumor that has grown outside the thyroid and into the blood vessels of the surrounding area would be categorized as T4.

With the help of the TNM system, your physician will determine your cancer's stage. For people aged 55 and younger, doctors only utilize stages I and II to account for this population. For those over age 55, doctors use stages I through IV.

  • Stage I: In those younger than 55, the cancer is any size and may or may not have spread to the lymph nodes, but has not spread to distant sites. In those older, the tumor must be small, confined to the thyroid, and have not spread to lymph nodes or distant sites.
  • Stage II: In those younger than 55, the cancer is any size and may or may not have spread to the lymph nodes but has spread to distant sites, including the blood, bones, or other internal organs. In those over 55, stage II means the tumor has not spread to distant sites but to nearby lymph nodes. The tumor may extend into the muscles in front of the thyroid.
  • Stage III: The cancer has spread beyond the thyroid into nearby structures that typically lie behind or to the side of the thyroid, including the larynx, trachea, esophagus, or recurrent laryngeal nerve, and may or may not have spread to nearby lymph nodes. It has not spread to distant sites.
  • Stage IVA: The cancer has spread extensively beyond the thyroid into the blood vessels or bone around the gland, may or may not have spread to nearby lymph nodes, and has not metastasized to distant sites.
  • Stage IVB: The cancer is any size and may or may not have spread to the nearby lymph nodes but has metastasized to distant organs, lymph nodes, or bones.

All anaplastic cancers are considered stage IV due to their poor prognosis, but there are substages within this depending on the size and spread of the tumor. Age is not a factor in the staging of medullary cancer, and follows a I through IV staging system with subdivisions within that.

Signs & Symptoms of Thyroid Cancer

Signs & Symptoms

In early stages of the disease, thyroid cancer typically does not cause any symptoms. As the cancer progresses, however, signs of thyroid cancer may become noticeable and include:

  • Pain in the neck and throat
  • Swelling in the neck
  • A lump in the neck that may grow quickly
  • Hoarseness or other vocal changes
  • Difficulty swallowing

Causes & Risk Factors

Causes & Risk Factors

Thyroid cancer occurs when DNA mutations cause cells in the thyroid to grow uncontrollably. The type of cancer depends on which cells mutate. There is no clear consensus on what causes these changes, but several risk factors have been associated with a higher chance of developing thyroid cancer.

These risk factors include:

  • Genetic factors - Several genetic conditions, including Cowden disease, multiple endocrine neoplasia, and familial adenomatous polyposis have been linked to an increased risk of thyroid cancer. A family history of thyroid cancer can also indicate you're at higher risk of the disease.
  • Iodine deficiency - Thyroid cancer rates are higher in areas where people's diets are low in iodine. Too much iodine, however, has also been linked to thyroid cancer.
  • Gender - Thyroid cancers occur in women about three times more often than in men
  • Age - The disease can develop at any age, but is most likely to occur in women between the ages of 40 and 60 and in men between the ages of 60 and 80
  • Radiation exposure - Radiation is a proven risk factor for thyroid cancer. Radiation from head or neck medical treatments or fallout from nuclear power plants are all possible radiation sources.



There is no way to prevent thyroid cancer, but if you're at a high risk of developing the disease, there are several ways to try and decrease that risk. If you're concerned about genetic factors that may contribute to thyroid disease, ask your doctor about genetic testing and increased screening for thyroid cancer so any possible tumors may be caught earlier.

Avoiding radiation exposure to the head and neck can help lower your risk. If you live near a nuclear power plant, some medicines can help block radiation from reaching the thyroid in the event of an accident.

Get Care

Trust NewYork-Presbyterian for Thyroid Cancer Care

At NewYork-Presbyterian, our thyroid cancer specialists are highly experienced in diagnosing all types of thyroid cancer and matching patients with the most effective therapies, which often result in a cure. We offer comprehensive care through the dedicated New York Thyroid Center at NewYork-Presbyterian Columbia University Medical Center and the Thyroid Disease Center at NewYork-Presbyterian Weill Cornell Medical Center. Make an appointment with us today.