About Thyroid Cancer — Risks, Statistics, Different Types

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Thyroid cancer refers to cancer that occurs in your thyroid gland. Your thyroid is a small, butterfly-shaped gland that is located in your neck. Its role is to facilitate the delivery of oxygen and energy to cells, tissues, glands, and organs, and the hormones it produces are essential for all of your body’s functions.

According to the American Cancer Society, the most recent statistics for thyroid cancer in the United States are:

  • An estimated 56,870 new cases of thyroid cancer (42,470 in women, and 14,400 in men) will be diagnosed in 2017.
  • An estimated 2,010 deaths from thyroid cancer (1,090 women and 920 men) will occur in 2017.

Some key information:

  • Thyroid cancer is more common when you are younger.
  • Two-thirds of those diagnosed are between the ages of 20 and 55.
  • Women are three times as likely to develop thyroid cancer than men.
  • Around 2 percent of thyroid cancer cases are diagnosed in children and teenagers.

The overall number of people diagnosed with thyroid cancer is increasing about six percent per year, and the total number of people diagnosed in 2016 was about double the number of people diagnosed in 1990. There is controversy regarding the reason for this increase. A minority of experts say that there is simply more thyroid cancer. The majority of researchers believe that the increase is due to better detection of small cancerous thyroid nodules via imaging tests, such as MRIs, CT scans, and ultrasounds.

Risk factors for thyroid cancer

There are a number of risk factors for thyroid cancer:

  • Gender: Women are more at risk than men.
  • Age: About two-thirds of thyroid cancer is diagnosed between the ages of 20 and 55.
  • Your family history: You are at increased risk if you have a family history of thyroid cancer.
  • Genetic mutation: Certain inherited genes put you at higher risk of some thyroid cancers.
  • Personal thyroid history: You are at a higher risk if you have Hashimoto’s disease or goiter.
  • Hypothyroidism with poor thyroid stimulating hormone (TSH) control: If you are hypothyroid and are untreated, or on insufficient levels of thyroid medication, having TSH levels that high-normal or above the reference range cutoff put you at higher risk factor for thyroid cancer.
  • Prior radiation treatment: Previous radiation treatments for cancer, acne, tonsils, and adenoids increase your risk for thyroid cancer
  • Prior radiation exposure: Being exposed to radiation from nuclear accidents or weapons testing— especially as an infant or child — is a thyroid cancer risk factor.
  • Chronic iodine deficiency: Chronic deficiency of iodine, a key nutrient, is a risk factor for thyroid cancer.
  • Other inherited health conditions: There are several inherited conditions associated with an increased risk of developing thyroid cancer, including familial adenomatous polyposis), Gardner syndrome, Cowden disease, and Carney complex.

The three categories of thyroid cancer

There are three different categories of thyroid cancer:

  • Differentiated thyroid cancers, including papillary or mixed papillary-follicular thyroid cancer, which makes up about 80 percent of thyroid cancer cases, and follicular thyroid cancer, which makes up about 15 percent of thyroid cancer cases
  • Medullary thyroid cancer, which makes up about 3 percent of thyroid cancer cases
  • Anaplastic thyroid cancer, which makes up about 2 percent of thyroid cancer cases

Papillary thyroid cancer

Papillary thyroid cancer is the most common type of thyroid cancer. Typically, this type of cancer is found in one of the two lobes of your thyroid gland, and in some cases, spreads into the nearby cervical lymph nodes. Papillary thyroid cancer usually grows very slowly and is less likely than other types of thyroid cancer to spread to other organs. It is considered very treatable and survivable. A mixed papillary-follicular cancer is a variant of papillary thyroid cancer and has similar features and a similar prognosis. This type of cancer is more often associated with radiation exposure.

Stage I indicates that cancer has not spread. Staging goes up to Stage IV, where cancer has spread to organs and the cancer has spread beyond the thyroid and lymph nodes. According to the American Cancer Society, based on the stage at first diagnosis, the following are the 5-year relative survival rates for papillary thyroid cancer.

  • Stage I: near 100 percent
  • Stage II: near 100 percent
  • Stage III: 93 percent
  • Stage IV: 51 percent

Follicular thyroid cancer

Follicular thyroid cancer is the second most common type of thyroid cancer. This type of cancer is more aggressive than papillary cancer and more likely to spread to organs than the lymph nodes. It is also considered very treatable, with high long-term survival rate. The best prognosis for follicular thyroid cancer is in those diagnosed at a younger age. This type of cancer is more often associated with iodine deficiency.

The following are the American Cancer Society’s 5-year relative survival rates for follicular thyroid cancer.

  • Stage I: near 100 percent
  • Stage II: near 100 percent
  • Stage III: 71 percent
  • Stage IV: 50 percent

Medullary thyroid cancer

Medullary thyroid cancer is the third most common type of thyroid cancer. Medullary thyroid cancer is more aggressive and can spread to the lymph nodes, liver, or lungs before a nodule is even detected and cancer diagnosed. About 75 percent of medullary thyroid cancer cases are considered sporadic, and not inherited. About one in four cases are “familiar medullary thyroid cancer,” which is inherited.

Treatment depends on the stage, and can include surgery, external beam radiation, and targeted drug therapy. RAI, however, is not typically performed, as it is not effective against this type of thyroid cancer.

The following are the American Cancer Society’s 5-year relative survival rates for medullary thyroid cancer.

  • Stage I: near 100 percent
  • Stage II: 98 percent
  • Stage III: 81 percent
  • Stage IV: 28 percent

Anaplastic thyroid cancer

Anaplastic thyroid cancer is the rarest, and most serious, thyroid cancer. Anaplastic thyroid cancer — which is often diagnosed based on a rapidly growing mass in the neck — is aggressive, and frequently spreads quickly to the lymph nodes and other organs. Unlike other types of thyroid cancer, anaplastic thyroid cancer is found most often in people over 60, and in men. Long-term survival rates are far less than for the other three types of cancer because treatment options are limited and often not effective.

The following are the American Cancer Society’s 5-year relative survival rates for medullary thyroid cancer.

  • All are Stage IV: 7 percent

Differentiated and undifferentiated thyroid cancer

According to the American Cancer Society, thyroid cancer is differentiated or undifferentiated. Differentiated thyroid cancer features cells that generally look like normal thyroid tissue. Papillary and follicular thyroid cancer are differentiated cancers. Anaplastic thyroid cancer is undifferentiated, with cells that do not resemble normal thyroid cells. Medullary thyroid cancer can be either differentiated, somewhat undifferentiated, or undifferentiated.

Signs and symptoms of thyroid cancer

Thyroid cancer does not always have symptoms, but if you do have symptoms, they can include:

  • A lump in your neck that you can see or feel
  • Pain in your throat or neck, sometimes radiating up to your ears
  • Enlarged lymph nodes
  • Swelling in your face
  • Swelling in your neck
  • A hoarse voice
  • Difficulty swallowing
  • Chronic diarrhea (in medullary cancer)
  • A rapidly enlarging lump, chronic coughing, coughing up blood (in anaplastic cancer)

How thyroid cancer is diagnosed

The process of diagnosing thyroid cancer typically follows a number of key steps:

  1. A nodule or lump is found.
  2. Your doctor conducts an examination.
  3. Blood tests arerun to assess your thyroid function.
  4. Imaging tests such asultrasound, MRI, or CT scan are performed to evaluate the nodule.
  5. Fine needle aspiration (FNA) biopsy is performed on suspicious nodules, followed by cytology to determine if cancer is present.
  6. Molecular testing is conducted on indeterminate or inconclusive samplesto determine if cancer is evident.
  7. Surgical biopsy is performed to remove the nodule or the lobe of the thyroid for cytology assessment in some cases.

Surgery

If thyroid cancer is conclusively diagnosed, the next step is almost always thyroid surgery — a thyroidectomy — to remove your thyroid. The extent of your thyroid surgery (partial or total removal) will depend on the type and stage of your cancer.

Thyroid cancer treatment

Treatment for thyroid cancer depends on the type of cancer, the size, and staging, among other factors.

Surgery: If it hasn’t already been performed, surgery to remove all or a portion of your thyroid is performed. In some cases, cervical lymph nodes are also removed during the surgery.

Radioactive iodine (RAI) remnant ablation: After surgery, you doctor may recommend “remnant ablation,” a radioactive iodine (RAI) treatment to eliminate any leftover thyroid tissue or affected lymph nodes.

Radiation and medications: For advanced thyroid cancers, cancers that do not respond well to RAI, or some cancers that have spread, other treatments are used, including external beam radiation and a number of drug treatments.

Thyroid hormone replacement: After a full thyroidectomy, you will be on prescription thyroid hormone replacement for life, to replace the missing thyroid hormone produced by the gland. Depending on the type of cancer, suppressive therapy may be recommended, with higher doses that keep your TSH very low to prevent thyroid cancer recurrence.

Thyroid cancer monitoring and follow-up

Thyroid cancer recurs in about 30 percent of people, but recurrence also is related to the type and staging of your cancer. After thyroid cancer treatment, your doctor will monitor you for a recurrence. This monitoring can include:

  • Periodic examination by your doctor, to physically assess your thyroid.
  • Thyroid blood testing to manage your thyroid medication dosage, as well as testing of calcitonin and thyroglobulin (Tg) levels, which can be used as cancer markers.
  • Periodic radioactive scans. Before a scan, you will be asked to follow a low-iodine diet and stop taking thyroid hormone replacement drugs until your TSH significantly increases, or replace your thyroid medication with the drug Thyrogen.
  • Periodic imaging tests, such as positron emission tomography (PET) scan, MRI or CT scans, to evaluate whether you have a recurrence or a spread to other organs.

The “good cancer” controversy

There is controversy among thyroid cancer patients regarding the medical community and media’s tendency to refer to thyroid cancer as “the good cancer.” This characterization is due to the very high cure and treatment rates associated with most types of thyroid cancer when compared to other, more common cancers. Some thyroid cancer patients reject this characterization, as it minimizes the impact of their thyroid cancer, especially the resulting lifelong hypothyroidism, or challenges of living with advanced or aggressive thyroid cancer.

Information and support

Thyroid cancer is still not very common, so it is important to become as knowledgeable as possible about your type of cancer, the treatment options, and how to optimize your health after thyroid cancer.

One highly recommended resource is the Thyroid Cancer Survivors’ Association, known as ThyCa. ThyCa has a website with in-depth information on thyroid cancer diagnosis and treatment, and its advisory board is made up of the nation’s leading experts on thyroid cancer. The group also holds an annual conference each fall, where thyroid cancer patients and caregivers learn about thyroid cancer diagnosis and treatment options from a range of top experts. ThyCa also has an excellent guide called the Thyroid Cancer Survivors’ Association: Thyroid Cancer Basics Handbook, available as a free PDF download.

You may also want to connect with the American Cancer Society, which has in-depth resources regarding thyroid cancer.

See more helpful articles:

Current Issues in Thyroid Cancer, With Dr. John C. Morris

Life After Thyroid Cancer: Patients Speak

How is Thyroid Cancer Treated?