What is the thyroid?
The thyroid is a hormone-producing organ (or gland) that is
located on the front of the neck, just under the Adam’s apple. The thyroid
gland, which is made up of a right lobe and a left lobe, produces and secretes
thyroid hormones into the bloodstream. Thyroid hormones are important to
functions that include regulating the metabolic rate and body temperature.
What is thyroid cancer?
Thyroid cancer occurs when cells of the thyroid gland grow
uncontrollably to form masses of cells called tumors that can invade the tissues
of the neck, spread to the surrounding lymph nodes, or to the bloodstream, and
then to other parts of the body. The most common types of cancers of the thyroid
gland are derived from the cells responsible for thyroid hormone production.
The most common kinds of thyroid cancer are papillary
adenocarcinoma of the thyroid and follicular adenocarcinoma of the thyroid. (Adenocarcinoma
is a general term for cancer that comes from glandular tissue.) Other kinds of
thyroid cancer are medullary and anaplastic.
What are the risk factors for thyroid cancer?
- Age—The majority of people diagnosed with this condition are over the
age of 40. Most people diagnosed with anaplastic thyroid cancer are over age
65.
- Gender—Women are about three times as likely as men to develop thyroid
cancer.
- Family history or genetic makeup—Thyroid cancer can sometimes run in
families. Rare gene changes in the RET, PTEN, or APC genes are
associated with an increased risk of thyroid cancer.
- Exposure to radiation—A history of exposure to radiation (especially
during childhood) is a very strong risk factor for thyroid cancer. Exposure
might have occurred during medical treatments or accidental exposure to
radioactive fallout from nuclear power plant accidents.
- Iodine deficiency—Iodine is necessary for thyroid hormone production.
Without enough iodine, the thyroid enlarges to form a mass called a goiter.
In the U.S., iodine is often added to table salt, preventing most Americans
from being deficient. In areas of the world where iodine deficiency occurs
more frequently, there are higher rates of goiters and slightly higher rates
of thyroid cancer.
What are the symptoms of thyroid cancer?
In most cases, no signs or symptoms will appear in the early
stages of thyroid cancer. Having one or more of the following symptoms does not
necessarily mean that thyroid cancer is present, as other conditions can cause
similar symptoms. However, one or more of the following might occur as thyroid
cancer grows:
- Pain in the lower front part of the neck
- Breathing problems
- Hoarseness or trouble swallowing
- Lump in the front of the neck below the Adam’s apple
- Swollen lymph nodes, especially in the neck
How is thyroid cancer diagnosed?
Nodules (or lumps in the thyroid) might be discovered by the
doctor during a routine exam or might be seen or felt by the patient. In some
cases, thyroid nodules are detected during tests to evaluate another head or
neck condition.
One or more of the following tests help to determine the nature of the nodule:
- Blood tests—Blood tests (thyroid function tests) can provide information
about the function of the thyroid gland. Also, if medullary cancer is
diagnosed using a biopsy (see below), you might have tests that check for
levels of calcitonin in the blood. That hormone is produced in high levels
with this form of thyroid cancer.
- Thyroid scans— With this scan, a special camera produces an image of the
thyroid on a computer screen using the radioactivity of iodine (given as a
pill). This test can determine which thyroid nodules will require biopsy and
which will not.
- Fine-needle aspiration (FNA) biopsy— During this procedure, the doctor
places a thin needle through the skin and into a nodule, removing a sample
of cells. The doctor might obtain tissue from different parts of the nodule.
The samples are sent to a laboratory for analysis.
- Surgical biopsy—If the FNA doesn't provide a certain diagnosis, the
doctor might operate to remove the nodule, which is then examined in a
pathology laboratory.
- Staging tests—After thyroid cancer is diagnosed, staging tests can help
determine whether the cancer has spread (metastasized). For papillary and
follicular cancers, a radioactive iodine whole bodyscan is often used for
staging. Imaging tests such as computerized tomography (CT) or magnetic
resonance imaging (MRI) are used in the staging of medullary cancer.
If a patient has familial (several members of the family have
medullary thyroid carcinoma) medullary thyroid cancer but does not test positive
for the RET gene mutation (see "risk factors for thyroid cancer" section), it is
still important for close family members to have their calcitonin levels tested.
This is generally done using a calcium infusion test. Although the calcitonin
level of healthy people rises slightly after an injection of calcium, it is much
higher in people with medullary thyroid cancer. In sporadic cases (only one
member of the family has the disease) negative for RET gene mutations, there is
no need to check family members.
What are the stages of thyroid cancer?
Once cancer of the thyroid is found and surgically removed,
additional testing will be completed to determine if cancer cells have spread to
other parts of the body. This information can be used for staging. A doctor
needs to know the stage of the disease in order to plan future treatment and
modes of follow-up. There are several staging systems for the papillary and
follicular thyroid cancers. It is important to know that most of them are
diagnosed in stage I.
The following stages are used to describe medullary cancers of the thyroid:
Stage I medullary
Cancer is less than 1 centimeter (about 1/2 inch) in size.
Stage II medullary
Cancer is between 1 and 4 centimeters (about 1/2 to 1 1/2 inches) in size.
Stage III medullary
Cancer has spread to the lymph nodes.
Stage IV medullary
Cancer has spread to other parts of the body.
There is no staging system for anaplastic cancer of the thyroid,
which is considered to be Stage IV thyroid cancer. This type of cancer of the
thyroid grows faster than the other types.
Recurrent thyroid cancer means that the cancer has come back (recurred) after it has been treated. It might come back in the thyroid or in another part of the body.
How is thyroid cancer treated?
The type of treatment used for thyroid cancer depends on the
stage of the disease. The following details cover treatments by stage:
Stage I and II papillary and follicular thyroid cancer - Treatment might be one of the following:
- Surgery to remove the thyroid (total thyroidectomy), followed by hormone
therapy and, in most cases, radioactive iodine
- Surgery to remove one lobe of the thyroid (lobectomy), followed by
hormone therapy, is used only in very small (less than 10 mm) stage I
cancers.
Stage III papillary and follicular thyroid cancer – Treatment might be one of the following:
- Surgery to remove the entire thyroid (total thyroidectomy) and lymph
nodes where cancer has spread, followed by radioactive iodine treatment.
- Total thyroidectomy followed by radioactive iodine and external-beam
radiation therapy
Stage IV papillary and follicular thyroid cancer – Treatment might be one of the following:
- Radioactive iodine
- External-beam radiation therapy
- Surgery to remove the cancer from places where it has spread
- Hormone therapy
- A clinical trial of new treatments, including chemotherapy
Medullary thyroid cancer – Treatment might be one of the following:
- Total thyroidectomy for tumors in the thyroid only, with possible
removal of lymph nodes in the neck
- For tumors that come back in the thyroid, radiation therapy as
palliative treatment (to relieve symptoms and improve the patient's quality
of life)
- For cancer that has spread to other parts of the body, chemotherapy as
palliative treatment (to relieve symptoms and improve the patient's quality
of life)
Anaplastic thyroid cancer – Treatment might be one of the following:
- Surgery to create an opening in the windpipe, for tumors that block the
airway (This surgery is called a tracheostomy.)
- Total thyroidectomy to reduce symptoms if the tumor is in the area of
the thyroid only
- External-beam radiation therapy
- Chemotherapy
- Clinical trials of chemotherapy and radiation therapy following
thyroidectomy
- Clinical trials studying new methods of treatment of thyroid cancer
Recurrent thyroid cancer – Treatment might be one of the following:
- Surgery with or without radioactive iodine (A second surgery might be
done to remove tumor that remains.)
- Radioactive iodine
- External-beam radiation therapy or radiation therapy given during
surgery to relieve symptoms caused by the cancer
- Injection of alcohol into the cancerous nodules in the neck
- Chemotherapy
- Clinical trials of new treatments
What are the survival rates for people with thyroid cancer?
The most common types of thyroid cancer can often be completely removed with surgery. Five-year survival rates for people with thyroid cancer exceed 90 percent.
Can thyroid cancer be prevented?
In many cases, it is not possible to prevent thyroid cancer. However, the following might help
reduce or eliminate the risk of thyroid cancer:
- Having preventive (prophylactic) surgery—A person with an RET gene
mutation might choose to have the thyroid removed with surgery.
- Taking potassium iodide tablets after exposure to large amounts of
radioactive iodine—Potassium iodide protects the thyroid gland from iodine
131, though not from other radioactive material. People who have
multinodular goiter, Graves' disease, or autoimmune thyroiditis should not
take potassium iodide tablets.
- Eating healthy foods—A diet high in fruits and vegetables and low in
animal fat can reduce your risk of many types of cancer. The American Cancer
Society recommends eating at least five servings of fruits and vegetables
every day. Unsaturated fats (omega-3 fatty acids), especially those found in
salmon and other fish, might help protect against cancer. Maintaining a
healthy weight can also help protect against many diseases, including cancer
of the thyroid.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 6/15/2008...#12210
