Thyroid Cancer

What You Need
To Know AboutTM
Thyroid
National Cancer Institute
Cancer
U.S. DEPARTMENT OF
HEALTH AND HUMAN SERVICES
National Institutes of Health

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Contents
About This Booklet 1
The Thyroid 2
Cancer Cells 2
Types of Thyroid Cancer 5
Risk Factors 6
Symptoms 8
Diagnosis 9
Staging 11
Treatment 13
Second Opinion 23
Follow-up Care 24
Sources of Support 26
The Promise of Cancer Research 28
Dictionary 30
National Cancer Institute Information Resources 39
National Cancer Institute Publications 40
U.S. DEPARTMENT OF
HEALTH AND HUMAN SERVICES
National Institutes of Health
National Cancer Institute

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About This Booklet
This National Cancer Institute (NCI) booklet is
about cancer* that begins in the thyroid. Each year in
the United States, more than 25,000 women and 8,000
men learn they have thyroid cancer.
This booklet tells about diagnosis, staging,
treatment, and follow-up care. Learning about the
medical care for thyroid cancer can help you take an
active part in making choices about your own care.
This booklet has lists of questions that you may
want to ask your doctor. Many people find it helpful to
take a list of questions to a doctor visit. To help
remember what your doctor says, you can take notes or
ask whether you may use a tape recorder. You may also
want to have a family member or friend with you when
you talk with the doctor—to take part in the discussion,
to take notes, or just to listen.
For the latest information about thyroid
cancer, please visit our Web site at
http://www.cancer.gov/cancertopics/types/thyroid.
Or, contact our Cancer Information Service. We
can answer your questions about cancer. We can
send you NCI booklets and fact sheets. Call
1–800–4–CANCER (1–800–422–6237) or instant
message us through the LiveHelp service at
http://www.cancer.gov/help.
*Words in italics are in the Dictionary on page 30. The Dictionary
explains these terms. It also shows how to pronounce them.
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The Thyroid
Your thyroid is a gland at the front of your neck
beneath your voice box (larynx). A healthy thyroid is a
little larger than a quarter. It usually cannot be felt
through the skin.
The thyroid has two parts (lobes). A thin piece of
tissue (the isthmus) separates the lobes.
The thyroid makes hormones:
• Thyroid hormone: Thyroid hormone is made by
thyroid follicular cells. It affects heart rate, blood
pressure, body temperature, and weight.
• Calcitonin: Calcitonin is made by C cells in the
thyroid. It plays a small role in keeping a healthy
level of calcium in the body.
Four or more tiny parathyroid glands are behind the
thyroid. They are on its surface. They make
parathyroid hormone, which plays a big role in helping
the body maintain a healthy level of calcium.
Cancer Cells
Cancer begins in cells, the building blocks that make
up tissues. Tissues make up the organs of the body.
Normal, healthy cells grow and divide to form new
cells as the body needs them. When normal cells grow
old or get damaged, they die, and new cells take their
place.
Sometimes, this orderly process goes wrong. New
cells form when the body does not need them, and old
or damaged cells do not die as they should. The build-
up of extra cells often forms a mass of tissue called a
growth or tumor.
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Thyroid
Larynx
Lymph nodes
Isthmus
Lobes
Parathyroid
glands
Isthmus
The pictures show the front and back of the thyroid.
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Growths on the thyroid are often called nodules.
Most thyroid nodules (more than 90 percent) are
benign (not cancer). Benign nodules are not as harmful
as malignant nodules (cancer):
• Benign nodules
—are rarely a threat to life
—don’t invade the tissues around them
—don’t spread to other parts of the body
—usually don’t need to be removed
• Malignant nodules
—may sometimes be a threat to life
—can invade nearby tissues and organs
—can spread to other parts of the body
—often can be removed or destroyed, but
sometimes the cancer returns
Cancer cells can spread by breaking away from the
original tumor. They enter blood vessels or lymph
vessels, which branch into all the tissues of the body.
The cancer cells attach to other organs and grow to
form new tumors that may damage those organs. The
spread of cancer is called metastasis.
See the Staging section on page 11 for information
about thyroid cancer that has spread.
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Types of Thyroid Cancer
There are several types of thyroid cancer:
• Papillary thyroid cancer: In the United States, this
type makes up about 80 percent of all thyroid
cancers. It begins in follicular cells and grows
slowly. If diagnosed early, most people with
papillary thyroid cancer can be cured.
• Follicular thyroid cancer: This type makes up
about 15 percent of all thyroid cancers. It begins in
follicular cells and grows slowly. If diagnosed early,
most people with follicular thyroid cancer can be
treated successfully.
• Medullary thyroid cancer: This type makes up
about 3 percent of all thyroid cancers. It begins in
the C cells of the thyroid. Cancer that starts in the
C cells can make abnormally high levels of
calcitonin. Medullary thyroid cancer tends to grow
slowly. It can be easier to control if it’s found and
treated before it spreads to other parts of the body.
• Anaplastic thyroid cancer: This type makes up
about 2 percent of all thyroid cancers. It begins in
the follicular cells of the thyroid. The cancer cells
tend to grow and spread very quickly. Anaplastic
thyroid cancer is very hard to control.
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Risk Factors
Doctors often cannot explain why one person
develops thyroid cancer and another does not.
However, it is clear that no one can catch thyroid
cancer from another person.
Research has shown that people with certain risk
factors are more likely than others to develop thyroid
cancer. A risk factor is something that may increase the
chance of developing a disease.
Studies have found the following risk factors for
thyroid cancer:
• Radiation: People exposed to high levels of
radiation are much more likely than others to
develop papillary or follicular thyroid cancer. One
important source of radiation exposure is treatment
with x-rays. Between the 1920s and the 1950s,
doctors used high-dose x-rays to treat children who
had enlarged tonsils, acne, and other problems
affecting the head and neck. Later, scientists found
that some people who had received this kind of
treatment developed thyroid cancer.
(Routine diagnostic x-rays—such as dental x-rays or
chest x-rays—use very low doses of radiation. Their
benefits usually outweigh their risks. However,
repeated exposure could be harmful, so it’s a good
idea to talk with your dentist and doctor about the
need for each x-ray and to ask about the use of
shields to protect other parts of the body.)
Another source of radiation is radioactive fallout.
This includes fallout from atomic weapons testing
(such as the testing in the United States and
elsewhere in the world, mainly in the 1950s and
1960s), nuclear power plant accidents (such as the
Chornobyl [also called Chernobyl] accident in
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1986), and releases from atomic weapons
production plants (such as the Hanford facility in
Washington state in the late 1940s). Such
radioactive fallout contains radioactive iodine
(I-131) and other radioactive elements. People who
were exposed to one or more sources of I-131,
especially if they were children at the time of their
exposure, may have an increased risk of thyroid
diseases. For example, children exposed to
radioactive iodine from the Chornobyl accident have
an increased risk of thyroid cancer.
For more information, you may want to read the
NCI fact sheet I-131 and Radioactive Fallout:
Questions and Answers. Page 40 tells how to get
NCI fact sheets.
• Family history of medullary thyroid cancer:
Medullary thyroid cancer sometimes runs in
families. A change in a gene called RET can be
passed from parent to child. Nearly everyone with
the changed RET gene develops medullary thyroid
cancer. The disease occurs alone as familial
medullary thyroid cancer or with other cancers as
multiple endocrine neoplasia (MEN) syndrome.
A blood test can detect the changed RET gene. If it’s
found in a person with medullary thyroid cancer, the
doctor may suggest that family members be tested.
For those who have the changed gene, the doctor
may recommend frequent lab tests or surgery to
remove the thyroid before cancer develops.
• Family history of goiters or colon growths: A
small number of people with a family history of
having goiters (swollen thyroids) with multiple
thyroid nodules are at risk for developing papillary
thyroid cancer. Also, a small number of people with
a family history of having multiple growths on the
inside of the colon or rectum (familial polyposis) are
at risk for developing papillary thyroid cancer.
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