Thyroid Cancer

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Introduction

Thyroid cancer is one of the least deadly types of cancer.  It occurs when cells in the thyroid gland grow abnormally and out of control.  Your thyroid gland is located in the front of your neck.  There are several different types of thyroid cancers and specific treatments for each.  Treatments may include surgery, radiation, radioactive iodine therapy, hormone treatments, and chemotherapy.
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Anatomy

Your thyroid gland is located in the front lower part of your neck, in front of your windpipe.  The thyroid gland is shaped like a butterfly.  It has two lobes, the right lobe and the left lobe.  A narrow isthmus joins the right and left lobes. 
 
The thyroid gland is mainly composed of two types of cells, thyroid follicle cells and C cells.  These cells produce hormones.  The thyroid hormones are secreted into your blood circulation and travel throughout your body.  They regulate the function of every cell and tissue.  Your thyroid produces thyroxine (T4) and triiodothyronine (T3), which are necessary for good health and control of your metabolism and energy levels.  C cells produce calcitonin, which helps to regulate calcium metabolism.
 
The hypothalamus and pituitary gland in your brain regulate T4 and T3 production.  When T4 and T3 levels are low, the hypothalamus produces thyrotropin-releasing hormone (TRH) to signal the pituitary gland to produce thyroid stimulating hormone (TSH).  The TSH travels in the bloodstream and signals the thyroid gland to produce more T4 and T3.  When T4 and T3 levels are high, the pituitary gland stops producing TSH.
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Causes

The exact cause of most thyroid cancers is unknown.  Cancer occurs when cells grow abnormally and out of control, instead of dividing in an orderly manner.  Thyroid cancer is more common in women than in men.  It occurs most frequently between the ages of 20 and 60 years old.

Some cases of thyroid cancer may be linked to changes in DNA.  Your DNA is the carrier of your genetic information, including directions for how your cells divide.  You inherited your DNA from your parents.  People with a family history of thyroid cancer have an increased risk for developing thyroid cancer.

Exposure to radioactivity from nuclear reactive material, nuclear plant accidents, or some types of radiation therapy for cancer can increase the risk for thyroid cancer.  In some parts of the world, diets that are low in iodine increase the risk for thyroid cancer.  This is not a concern in the United States, since iodine is contained in table salt and many of the foods we eat.

There are several types of thyroid cancer.  Some of the more common types of thyroid cancer include:

Papillary carcinoma

The majority of thyroid cancers are papillary carcinomas.  They occur most frequently in women of childbearing age.  Papillary carcinoma originates in the thyroid follicle cells.  It is generally a very slow growing cancer that may gradually spread to other parts of the body.  Papillary carcinoma tends to spread to the lymph nodes in the neck, most of the time this is very treatable.  Papillary cancer is the least likely type of thyroid cancer to cause death.

Follicular carcinoma
Follicular carcinoma is the second most common type of thyroid cancer.  It is more common in countries where people do not eat enough iodine in their diets.  This is not a common situation in the United States where people ingest iodine in table salt and food on a regular basis.  Follicular carcinoma usually remains in the thyroid gland, but it may spread to the lungs and bone.  Follicular carcinoma tends to return.  Cancer that comes back after treatment is termed recurrent

Medullary carcinoma of the thyroid (MCT)
MCT develops in the C cells of the thyroid gland.  MCT can quickly spread to the lymph nodes, liver, and lungs.  Most cases of MCT are sporadic.  However, isolated familial medullary thyroid carcinoma (FMTC) is a type of thyroid cancer that is inherited and can occur in each generation of a family.  MCT does not respond to radioactive iodine treatments and tends to have a poor prognosis.

Anaplastic carcinoma
Anaplastic carcinoma is also called undifferentiated thyroid cancer, giant cell cancer, and spindle cell cancer.  It is rare.  Anaplastic carcinoma is an aggressive cancer.  It can spread very quickly to nearby throat and neck structures.  Anaplastic carcinoma does not respond to radioactive iodine treatments.  It is the most deadly form of thyroid cancer.

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Symptoms

Symptoms of thyroid cancer may vary depending on the type of thyroid cancer.  Some types of thyroid cancer do not cause symptoms in the early stages.  Thyroid cancer may cause a lump or nodule in the neck.  The thyroid gland may appear enlarged and your neck may swell.  It may be difficult for you to breathe and feel like you are breathing through a straw.  You may have problems swallowing.  Your voice may change and sound hoarse.  You may experience coughing without a cold or coughing with blood.  The front of your neck may feel painful.  The pain may spread up to your ears.  Thyroid cancer may cause changes related to hormone release.
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Diagnosis

You should contact your doctor if you develop the symptoms of thyroid cancer.  You should ask your doctor to check your thyroid during each of your regular physical examinations.  Your doctor will review your medical history.  It is very important to tell your doctor if any of your relatives have thyroid cancer.  You should tell your doctor about your risk factors and symptoms.  Your doctor will examine your thyroid by gently feeling your neck.  The firmness and size of your thyroid, as well as any enlarged lymph nodes will be noted.  A biopsy may be used to determine if a lump or nodule is cancerous.  Imaging tests may be used to help diagnose thyroid cancer.  An ultrasound is used to check the number and size of thyroid nodules.  It creates pictures from sound waves transmitted by a device that is placed gently on your throat.  A thyroid scan is a procedure that uses a small amount of radioactive iodine and a special camera.  A thyroid scan can be helpful for determining if cancer has spread.  Your blood may be tested to evaluate how your thyroid is functioning.
 
A biopsy involves removing a sample of cells and fluid to be examined for cancer.  Your doctor will perform a fine needle aspiration.  After numbing your skin, your doctor will place a thin needle in the nodule and withdraw fluid and cells. This takes about 10 seconds.  The procedure may be repeated a few times to take samples from different areas of the tumor.
 
Computed tomography (CT) scans and positron emission tomography (PET) scans are used to determine if cancer has spread. Magnetic resonance imaging (MRI) scans provide a very detailed picture of thyroid cancer.  In some cases, it may identify if a tumor is cancerous or not.  MRIs are also used to see if the cancer has spread to other structures in the body.  CT, PET, and MRI scans are painless procedures and they require that you remain motionless while the images are taken.
 
If you have thyroid cancer, your doctor will assign your cancer a classification stage based on the results of all of your tests.  Staging describes the cancer and how it has metastasized.  Cancer that has spread from its original site to other parts of the body is termed metastasized cancer.  Staging is helpful for treatment planning and recovery prediction. 
 
There is more than one type of staging system for cancer, and you should make sure that you and your doctor are referring to the same one.  Generally, lower numbers in a classification system indicate a less serious cancer, and higher numbers indicate a more serious cancer.  The stages may be subdivided into classifications that use letters and numbers.
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Treatment

The type of treatment that you receive depends on the type of thyroid cancer that you have.  Surgery is the main treatment for all types of thyroid cancer.  Surgery is used to remove all of the tumor and all or part of the thyroid gland.  Cancerous lymph nodes are surgically removed as well.
 
Radioactive iodine therapy is used to destroy any thyroid cancer that remained after surgery and cancer that has spread to other parts of the body.  Radioactive iodine is given in a pill.  Research shows that radioactive iodine therapy can improve the survival rate of people with papillary or follicular thyroid cancer that has spread. 
 
If your thyroid gland is partially or completely removed, you will need to take daily thyroid hormone replacement pills.  Thyroid hormone therapy is also used to lower blood TSH levels to help keep the cancer from recurring.  This process is called suppressive therapy.  It is safe and has few side effects.
 
External beam radiation therapy is most frequently used for thyroid cancers that do not respond to radioactive iodine therapy.  External beam radiation uses high-energy beams to disrupt the growth of cancer cells.  Radiated cancer cells are not able to repair themselves or replicate.  Radiation damages all cells- both healthy and cancerous, in the exposed area.  To reduce side effects of fatigue and sunburn, your doctor will figure out the exact dose of radiation that you need and configure the beam to target your cancer as accurately as possible.  External radiation therapy usually involves receiving treatments five days a week for about six weeks.
 
Chemotherapy may be used to treat thyroid cancers that do not respond to surgery or radiation and has spread to other parts of the body.  It is most frequently used for anaplastic thyroid cancer, but is rarely helpful for other types of thyroid cancer.  Chemotherapy uses a combination of drugs that are administered over a period of time.  Chemotherapy kills cancer cells, but they also damage healthy cells.  The healthy cells are capable of repairing themselves, but the cancer cells are not.  The side effects of chemotherapy depend on the amount and type of medication that you receive.  Your doctor can prescribe medication to help prevent side effects before you receive chemotherapy.
 
Follow-up care is very important after treatment of thyroid cancer.  Thyroid cancers can grow very slowly and may recur even after 10 to 20 years following treatment.  With treatment, the outcome for the majority of thyroid cancers is good.  Your doctor will let you know what to expect.
 
The experience of thyroid cancer and cancer treatments can be an emotional process for people with cancer and their loved ones.  It is important that you receive support from a positive source.  Some people find comfort in their family, friends, counselors, co-workers, and faith.  Cancer support groups are another good option.  They can be a source of information and support from people who understand what you are experiencing.  Ask your doctor for cancer support group locations in your area.
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Prevention

Because the exact cause of most thyroid cancers is unknown, it is not possible to reliably prevent thyroid cancer at this time.  If you have a family history of thyroid cancer, you should ask your doctor about genetic blood testing.  Many cases of thyroid cancer can be prevented early.  Know the symptoms of thyroid cancer and contact your doctor if you have concerns.  Make sure that your doctor checks your thyroid during your routine physical exams.

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Am I at Risk

Most people that develop thyroid cancer have no apparent risk factors.  However, researchers have identified risk factors that may increase the likelihood of developing thyroid cancer.  People with all of the risk factors may never develop the condition; however, the chance of developing thyroid cancer increases with the more risk factors you have.  You should tell your doctor about your risk factors and discuss your concerns.


Risk factors for thyroid cancer:


_____ Thyroid cancer is three times more common in women than in men.
_____ Most cases of thyroid cancer occur in people between the ages of 20 and 60.
_____ Follicular thyroid cancer is more common in people with a low-iodine diet. Papillary thyroid cancer is more common in people with a low-iodine diet that have been exposed to radioactivity.  In the United States, people consume iodine in salt and foods so this is not as great of a risk factor as it may be for people living in other parts of the world.
_____ During the 1950s, radiation treatments were used to treat acne, fungus infections of the scalp, and enlarged glands or tonsils. Adults that received head and neck radiation treatments in childhood have an increased risk for developing papillary thyroid cancer.
_____ Children that receive low dose radiation treatments for non-Hodgkin’s lymphoma have an increased risk of developing thyroid cancer.
_____ People that have been exposed to radioactive fallout from nuclear reactive material, nuclear weapons testing, or power plant accidents have an increased risk for developing thyroid cancer. 
_____ An inherited abnormal gene causes some medullary thyroid cancers.  If familial medullary thyroid carcinoma (FMTC) runs in your family, ask your doctor to get tested.
_____ Gardner syndrome, familial polyposis, and Cowden disease are inherited genetic conditions that are associated with higher rates of thyroid cancer.
_____ Certain families appear to have an excess number of papillary thyroid cancers.  Researchers have not identified the genetic link as of yet.  However, you should let your doctor know if your relatives have thyroid cancer.

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Complications

Some types of thyroid cancer can spread to other parts of the body, including the lungs, bones, lymph nodes, and liver.  In some cases, thyroid cancer may come back after treatment.  Such cancers are termed recurrent.  Thyroid cancer usually returns in the neck, but it may also reappear in another part of the body, such as the lungs, bones, lymph nodes, and liver.
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Advancements

Researchers are studying ways to identify exactly what causes thyroid cancer.  They are conducting clinical trials to identify the most beneficial treatment.  Genetic studies have already revealed the cause of familial MTC, and researchers hope to understand the genetic processes involved in other types of thyroid cancers. 
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This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

The iHealthSpot patient education library was written collaboratively by the iHealthSpot editorial team which includes Senior Medical Authors Dr. Mary Car-Blanchard, OTD/OTR/L and Valerie K. Clark, and the following editorial advisors: Steve Meadows, MD, Ernie F. Soto, DDS, Ronald J. Glatzer, MD, Jonathan Rosenberg, MD, Christopher M. Nolte, MD, David Applebaum, MD, Jonathan M. Tarrash, MD, and Paula Soto, RN/BSN. This content complies with the HONcode standard for trustworthy health information. The library commenced development on September 1, 2005 with the latest update/addition on February 16, 2022. For information on iHealthSpot’s other services including medical website design, visit www.iHealthSpot.com.