What Is Anaplastic Thyroid Cancer?

Medically Reviewed by Carol DerSarkissian, MD on May 27, 2020

Anaplastic thyroid cancer is an extremely rare and fast-growing cancer. Just 500-800 people in the U.S. are diagnosed with it each year.

It’s also very deadly. Anaplastic thyroid cancer makes up only 1%-2% of all types of thyroid cancer. But it accounts for as much as half of all thyroid cancer deaths in the country.

The word anaplastic describes cancer cells that multiply quickly and that are very different from normal cells. Anaplastic thyroid cancer is also called undifferentiated thyroid cancer.


This cancer starts in the thyroid, a butterfly-shaped gland at the base of your neck. The thyroid’s job is to make hormones that flow through your bloodstream. These hormones help your heart, brain, and other organs work. They also help you stay warm and burn energy.

Scientists don’t really know what causes anaplastic thyroid cancer. Often, something faulty has happened to the thyroid gland before the cancer starts. It can form in an enlarged thyroid, called a goiter. Other times, anaplastic thyroid cancer can grow from other types of thyroid cancer that started there first.


You can have most types of thyroid cancers and not know it. But anaplastic thyroid cancer often grows quickly and cause symptoms that may include:

  • Cough, with or without blood
  • Trouble swallowing
  • Hoarse or changed voice
  • Loud or troubled breathing
  • Lump in your lower neck
  • Pain or pressure in your neck
  • Food or pills getting “stuck” when you swallow
  • Shortness of breath when you’re lying flat

Risk Factors

Certain things can raise your chances of anaplastic thyroid cancer. They include:

Age. Most cases happen in people ages 60-70 years old.

Gender. Women are more likely than men to get it.

Medical history. Previous cases of goiter or other forms of thyroid cancer raise your risk for anaplastic thyroid cancer. A goiter can be caused by a lack of iodine. But in the U.S., it more often results from your thyroid making too much or too little hormones, or from nodules in your thyroid.

Radiation. Your risk is higher if you’ve had radiation treatment to your head and neck area or been exposed to radioactive materials.

Blood type. One study found that people in the type B blood group may have higher chance of getting this cancer.


Anaplastic thyroid cancer can spread rapidly in a matter of weeks. So it’s important to see your doctor right away. They will examine you and check for a lump or growth in your neck.

Diagnostic tests for anaplastic thyroid cancer include:

  • Biopsy. This takes a sample of your thyroid gland tissue with a needle to examine under a microscope for cancerous cells.
  • Imaging tests such as MRIor CT scans
  • Laryngoscopy, which looks at your airway through a special scope threaded into your throat
  • Thyroid scan, which shows if the tumor absorbs a radioactive substance. If it doesn’t, it’s cancerous.


This cancer can be hard to treat because it grows fast and unpredictably.

The best treatment is to take out all the cancerous tumors with surgery. But if your cancer has spread into other parts of your neck, chest, and elsewhere, you likely will need chemotherapy or radiation therapy, or both. But in most cases, chemotherapy and radiation therapy do not help much.

Sometimes, you might need surgery to help you breathe more easily or to eat.

Another option is to ask your doctor about enrolling in a clinical trial. These studies test unproven medications and therapies that might work better to fight your cancer.


Anaplastic thyroid cancer is extremely aggressive. Most people live months, not years, after their diagnosis.

The 5-year relative survival rate is 7%. That means that 7 out of 100 people live at least 5 years after their diagnosis.

Survival rates differ widely depending on how far the cancer has spread. If the cancer is localized and confined to your thyroid, your 5-year relative survival rate is 31%.

For regional cancers that have spread beyond the thyroid to nearby locations, 12 out of 100 people are alive 5 years later. But if the cancer has reached your bones or other distant locations, the survival rate falls to 4%.

WebMD Medical Reference



University of Texas MD Anderson Cancer Center: “Q&A: Anaplastic Thyroid Cancer.”

National Cancer Institute: “Anaplastic Thyroid Cancer,” “NCI Dictionary of Cancer Terms.”

American Thyroid Association: “Thyroid Cancer.”

U.S. National Library of Medicine: “Anaplastic Thyroid Cancer.”

Columbia University Irving Medical Center: “Anaplastic Thyroid Cancer.”

National Center for Advancing Translational Sciences: “Anaplastic Thyroid Cancer.”

Journal of Oncology: “Anaplastic Thyroid Cancer: A Review of Epidemiology, Pathogenesis, and Treatment.”

Mayo Clinic: “Goiter.”

American Cancer Society: “Thyroid Cancer Survival Rates, by Types and Stage.”

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