Thyroid Tumors

What are thyroid nodules?

Thyroid nodules or lumps are very common. As many as 5 percent of the North American population may have a thyroid nodule. When a nodule is felt in the neck a concern is raised about the possibility of cancer. However, most nodules are not cancer. Other causes for these nodules include cysts, thyroiditis, nodular goiter, adenomatous nodules, follicular adenomas and Hürthle cell adenomas. All of these conditions are benign.

Even though as many as ten million people in the United States may have a palpable thyroid nodule there are only about 25,690 new thyroid cancers expected to be diagnosed in 2005. Most thyroid cancers are able to be treated and are not a real threat to the patient if they are managed appropriately. When a thyroid nodule is found, the first step is for a doctor to take a detailed history from the patient.

Most nodules that occur between the ages of 30 and 50 are benign. When nodules occur in the very young or very old there is a greater worry about the possibility of cancer. Benign nodules are more common in both men and women but nodules are five times more frequent in females. Therefore the proportion of malignant nodules in males is twice that of females.

One of the most important aspects is whether a patient has received prior radiation to the head and neck area. This has been clearly associated with an increased risk of both benign and malignant nodules. For a patient with a solitary nodule who has had prior radiation exposure, the prevalence of cancer is 30-50 percent.

If there is a history of other endocrine problems such as pheochromocytoma or hyperparathyroidism, the patient may have a multiple endocrine neoplasia syndrome, which increases the possibility of thyroid cancer.

What are thyroid adenomas?

Thyroid adenomas grow from the cell layer that lines the inner surface of the thyroid gland. The adenoma itself secretes thyroid hormone. If the adenoma secretes enough thyroid hormone, it may cause hyperthyroidism. Thyroid adenomas may be treated if they cause hyperthyroidism. Treatment may include surgery to remove the part of the thyroid with the overactive nodule.

What are cancerous thyroid tumors?

A nodule that has been stable in size for years is almost always benign. Rapid development of a nodule would suggest a cyst or a hemorrhage. Thyroid cancer usually develops over weeks or months. If there is difficulty swallowing, speaking or breathing these symptoms are more worrisome for thyroid cancer. Nodules that are hard when felt during the examination and that are fixed to surrounding tissue such as the muscles of the neck are more likely to be cancerous. The presence of a single nodule is more likely to be associated with a cancer diagnosis. 

Cancer of the thyroid occurs more often in people who have undergone radiation to the head, neck, or chest. However, most thyroid cancer can be cured with appropriate treatment. Thyroid cancer usually appears as small growths (nodules) within the thyroid gland.

The symptoms of thyroid cancer may resemble other conditions or medical problems. Always consult your physician for a diagnosis.

What are the different types of thyroid cancer?

The National Cancer Institute (NCI) describes the major types of thyroid cancer as follows:

papillary and follicular variant of papillary thyroid cancers 
These two types of thyroid cancer account for 80 percent to 90 percent of all thyroid cancers. Papillary thyroid cancer is the more common of the two types. Both types begin in the follicular cells of the thyroid and tend to grow slowly. 

follicular thyroid cancer
This type of thyroid cancer occurs most often among elderly patients and accounts for about 15 percent of thyroid cancers. This type of thyroid cancer is more aggressive and tends to spread through the bloodstream to other parts of the body.

medullary thyroid cancer
This type of thyroid cancer accounts for 5 percent to 10 percent of all thyroid cancers. Medullary thyroid cancer is the only thyroid cancer that begins in the C cells. This type of thyroid cancer is easier to control if it is found and treated early, before it spreads to other parts of the body. There are two types of medullary thyroid cancer: sporadic medullary thyroid cancer and familial medullary thyroid cancer (FMTC). Because familial medullary thyroid cancer tends to run in families, screening tests for genetic abnormalities in the blood cells may be conducted. 

anaplastic thyroid cancer
This rare type of thyroid cancer accounts for about 1 percent to 2 percent of all thyroid cancers. Anaplastic thyroid cancer begins in the follicular cells and tends to grow and spread very quickly.

Diagnosis of thyroid cancer:

Most blood tests are normal in patients with a solitary thyroid nodule. Blood studies to measure thyroid function can determine if the patient has a hyper or overactive thyroid or a hypo or under active thyroid. The best test for doing this is measurement of thyroid stimulating hormone or TSH. TSH is low in hyperthyroidism and high in hypothyroidism.

There are a number of ways that the thyroid gland and the nodule can be visualized radiologically. One is ultrasound of the neck. This can be done in the office and can show if a nodule is present and whether it is solid or cystic by passing sound waves from a transducer through the neck and back to the transducer.

A thyroid scan can show if a nodule functions like normal thyroid tissue. It does this because the thyroid takes up a radio labeled isotope preferentially. This can be measured with a gamma counter, which is like a Geiger counter. If the thyroid nodule does not function it is called cold. If it functions more than normal tissue it is called hot. Hot nodules are almost never malignant. Cold nodules may harbor cancer but most do not.

The best way to diagnose the nature of a nodule is to do a fine needle aspiration biopsy (FNA). This is an office procedure that uses the same needles for drawing blood to take some cells from the thyroid nodule. These can be looked at under the microscope by a cytologist. The cellular features can be used to confirm that the nodule is benign, to diagnose a cancer, or to diagnose a follicular neoplasm. This latter diagnosis is really indeterminant because the cells of a benign follicular tumor and a malignant follicular tumor look quite the same and the whole tissue has to be examined under the microscope to determine whether a cancer is present.

Small nodules that have been diagnosed benign by fine needle aspiration biopsy do not usually require surgery. Surgery is the preferred treatment for thyroid nodules that are cancerous, suspicious for cancer, or are non cancerous but large enough to cause symptoms such as difficulty breathing or swallowing. Enlargements of the thyroid that have moved down into the chest are called substernal goiters. These should be removed because they often cause symptoms and it is very difficult to be sure they are not increasing in size since they cannot be felt.

People who have thyroid nodules after having had radiation exposure to the head, neck or chest should also undergo surgery because of their high risk of having thyroid cancer. Most thyroid cancers grow and spread slowly so that delaying surgery a short time for a suspicious nodule does not really pose a health risk for the patient. If there is a delay, it is a good idea to take thyroid hormone replacement to put the thyroid gland at rest. Taking these pills replaces the normal thyroid function and avoids stimulation to the growth of the thyroid or the nodule. Thyroidectomy can also be used to treat hyperthyroidism.

Summary:

In addition to a complete medical history and physical examination, diagnostic procedures for thyroid cancer may include:

• blood tests - to evaluate the level of thyroid-stimulating hormone (TSH), calcium, calcitonin (a hormone produced by normal C cells of the thyroid gland), and other substances in the blood such as thyroglobulin.
• thyroid scan - a type of nuclear scan that examines the thyroid after a person is given (by mouth or intravenously) a small amount of radioactive material that contains iodine or technetium. For a short period, the radioactive material emits radiation. A special camera, called a gamma camera, is used to determine the amount of radiation that has been absorbed by thyroid nodules. Cold nodules are nodules that absorb less radioactive material than the surrounding thyroid tissue. Hot nodules are nodules that absorb more radioactive material. 
• ultrasound (also called sonography.) - a diagnostic imaging technique that uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels. 
• biopsy - a procedure in which tissue samples are removed (with a needle or during surgery) from the body for examination under a microscope to determine if cancer or other abnormal cells are present. 

Treatment for thyroid cancer:

Thyroid surgery is most often done under general anesthesia although it can be done under local. The operation is done through a small incision made in the lower neck. This area of the body heals quite well and often these incisions cannot even be seen when they are healed. The muscle and other tissue are separated to expose the thyroid gland.

A total lobectomy and isthmusectomy is the minimum procedure that is recommended if there is a nodule in one lobe of the thyroid. The isthmus is the narrow band of tissue connecting the two lobes of the thyroid. Removed tissue is always examined under a microscope to determine whether cancerous cells are present.

If cancer is present the surgeon will usually perform a total thyroidectomy. In this operation the entire gland is removed. This is done when the thyroid gland contains cancer or when there is a high risk of developing thyroid cancer or when there are nodules in both lobes of the thyroid. If the patient does have cancer and it has spread to the lymph nodes, these lymph nodes are removed with a procedure called a neck dissection. The lymph nodes in the center part of the neck are removed with a central neck dissection. The lymph nodes in the lateral part of the neck are removed with a modified neck dissection that preserves the muscle and vessels and nerves in that part of the neck.
Many patients can go home on the day of their surgery if they have only had a lobectomy. For a total thyroidectomy, most patients should stay overnight until they have recovered from their anesthesia and operation. Patients usually return quite quickly to their normal activity after thyroid surgery.

Thyroid surgery is generally quite safe. There are some very special risks associated with it. Hoarseness and change of voice can occur because the nerves that go to the voice box or larynx lie at the back of the thyroid gland. It can be damaged during thyroid surgery. The more experience your surgeon has, the less risk there is.

Summary:

Specific treatment for thyroid tumors will be determined by your physician based on:

• your age, overall health, and medical history
• extent of the disease
• your tolerance for specific medications, procedures, or therapies
• expectations for the course of the disease
• your opinion or preference

Treatment may include one or more of the following:

• surgery - to remove all or part of the thyroid. Types of thyroid surgery include:
• total thyroidectomy – removal of the entire thyroid and sometimes the nearby lymph nodes. 
• lobectomy - removal of the lobe with the cancerous nodule. The nearby lymph nodes and part of the remaining thyroid tissue may also be removed.
• modified neck dissection- the removal of cancer involved lymph nodes in the lateral neck saving muscles, nerves and blood vesels.
• radioactive iodine therapy (also called radioiodine therapy) - a treatment in which small amounts of radioactive iodine (I-131) is given (usually in a capsule or liquid) to destroy any normal thyroid or cancer cells that have not been removed by surgery or have spread to other parts of the body. radioactive iodine therapy is usually not used to treat medullary or anaplastic thyroid cancer.
• external radiation (external beam therapy) - a treatment that precisely sends high levels of radiation directly to the cancer cells. The machine is controlled by the radiation therapist. Since radiation is used to kill cancer cells and to shrink tumors, special shields may be used to protect the tissue surrounding the treatment area. Radiation treatments are painless and usually last a few minutes. This has a very limited role for most thyroid cancers.
• thyroid hormone therapy - hormones are given to prevent, slow, or stop cancer cells from growing. Hormone therapy as a cancer treatment inhibits or blocks any stimulating substances such as TSH that would promote the growth of the thyroid cancer. Thyroid hormone therapy may be used to treat papillary and follicular thyroid cancer. This therapy may also be necessary after surgery or radioactive iodine therapy to replace the natural or body’s own production of thyroid hormone. 
• chemotherapy - the use of anticancer drugs to treat cancerous cells. In most cases, chemotherapy works by interfering with the cancer cell’s ability to grow or reproduce. Different groups of drugs work in different ways to fight cancer cells. The oncologist will recommend a treatment plan for each individual. This has a very limited role for most thyroid cancers.

Click here to view the
Online Resources page of this Web.

Cancer Care at Rush

When it comes to treating cancer, experience matters. And Rush University Medical Center in Chicago, Illinois, has it, with one of the Midwest’s largest and most comprehensive cancer treatment programs, combining leading-edge therapies with vital emotional support.

For more information, visit the Cancer Programs home page.

Looking for Other Health Information?

• Visit our Health Information home page.
   
  or
  
 

• Visit Discover Rush’s Web Resource page to find articles on health topics and recent health news from Rush University Medical Center in Chicago, Illinois. You will also find many helpful links to other areas of our site.

Looking for a Doctor?

Rush University Medical Center in Chicago, Illinois, is a leader in caring for people of all ages, from newborns through older adults.

Just phone (888) 352-RUSH or (888) 352-7874 for help finding the Rush doctor who’s right for you.