Thyroid Cancer: The Facts

What is it?

Thyroid Cancer occurs when cancer cells are found in the tissues of the thyroid gland. The thyroid gland is located at the base of your throat and is made of two lobes, a right lobe and a left lobe. The lobes are joined together by a narrow piece of tissue called the isthmus. The purpose of the thyroid gland is to absorb iodine from your bloodstream and to produce hormones that are important for many body functions such as heart rate, blood pressure, temperature and metabolism. There are four different types of cancer that can be found in the thyroid gland. These different categories are determined by the type of cells that are affected.

PAPILLARY CARCINOMA

Papillary carcinoma is the most common type of thyroid cancer. It develops from thyroid follicle cells and usually grows very slowly. With most papillary carcinomas, only one lobe of the thyroid gland is involved, but in about 10-20% of papillary carcinomas, both lobes are involved. If detected early, the survival rate is very high.

FOLLICULAR CARCINOMA

Follicular Carcinoma is the second most common type of thyroid cancer. This type of thyroid cancer is usually confined to the thyroid gland, but can spread to other areas of the body, such as the lungs or bone. Follicular Cancer very rarely spreads to the lymph nodes.

ANAPLASTIC CARCINOMA

Anaplastic Carcinoma is a rare form of thyroid cancer. Research shows it develops from an existing papillary or follicular cancer. This is a very aggressive type of thyroid cancer that commonly spreads throughout the neck and often to other areas of the body. Anaplastic carcinoma is also known as Undiffereniated Thyroid Cancer. It occurs more frequently in older people.

MEDULLARY CANCER

Medullary Cancer (MTC) develops from the C-cells, sometimes called calcitonin-producing parafollicular cells, which are found in the thyroid gland and are responsible for 5-10% of thyroid cancer cases. Medullary Cancer can spread to the lymph nodes, the lungs, or the liver before a thyroid nodule has been detected or a screening test is done. MTC can also spread to the bone, brain, and adrenal medulla. This type of thyroid cancer is easier to control if detected in the early stage and has not spread to other areas of the body.

There are two types of MTC. The first type represents 80% of all medullary thyroid cancers, and is called sporadic medullary thyroid cancer. This type of MTC is not inherited and occurs most frequently in one thyroid lobe in older adults.

The second type of MTC has a hereditary basis and can occur in each generation of a family. This inherited type of MTC can develop from a change or alteration in a gene called RET. Almost everyone who has the altered RET gene will develop medullary thyroid cancer. The RET gene can be detected with a blood test. If this altered gene is detected in a person with medullary cancer, the physician may encourage other family members to be tested for the altered RET gene. When MTC occurs in a family, it may be called "familiar medullary cancer" or "multiple endocrine neoplasia (MEN) syndrome". Individuals diagnosed with MEN syndrome have a higher risk of developing other cancers in the endocrine organs, such as the adrenal glands and the pancreas.

Who gets it?

The exact cause of Thyroid Cancer is unknown. Each year in the U.S., 14,000 women and 4,600 men are diagnosed with Thyroid Cancer. There are certain risk factors that increase the probability of developing Thyroid Cancer.

• Females are at a 2-3 times more likely to develop Thyroid cancer than men.
  
  
• People 40 years or older are at risk for developing Thyroid cancer. People older than 65 years are at risk for Anaplastic Thyroid cancer.
  
  
• Caucasians are more likely than African Americans to develop thyroid cancer.
  

Other factors also contribute to the likelihood of developing thyroid cancer.

Radiation Exposure - People who have been exposed to high levels of radiation to the neck through x-rays. Routine diagnostic x-rays use very small doses of radiation, however repeated exposure could be harmful. Radioactive fallout from atomic weapons testing, nuclear power plant accidents, and released from atomic weapons production plants. This type of radioactive fallout contains radioactive iodine (I-131). People exposed to I-131, especially children, may be at increased risk for developing thyroid cancer. People exposed to radiation are more likely to develop papillary or follicular thyroid cancer.

Family History - Medullary thyroid cancer can be caused by a change or alteration in a gene called RET. Altered RET genes can be passed from a parent to a child. Almost all individuals with the altered RET gene will develop medullary thyroid cancer. A blood test can detect an altered RET gene.

Decreased iodine in the diet - When an individual does not have enough iodine in their diet, they develop goiters. The risk of developing thyroid cancer is increased.

SYMPTOMS

Early thyroid cancer does not usually produce symptoms. As Thyroid Cancer develops, an individual may experience the following symptoms:

• A lump may be found in the front of the neck, near the Adam's apple. This bulge is sometimes called a "goiter." Most goiters are benign.
  
• Hoarseness or difficulty speaking with a normal voice.
  
• Swollen lymph nodes, particularly in the neck.
  
• Difficulty swallowing or breathing.
  
• Pain experienced in the throat or neck.
  

These symptoms may not be the result of cancer. It is important to be evaluated by a doctor so the cause of the symptoms may be identified.

How is it detected?

DIAGNOSTIC TESTS:

• Physical exam - The doctor will examine the neck for unusual growths or swelling. The areas that will be examined are: the neck, thyroid, voice box and lymph nodes.
  
  
• Blood tests - A Doctor or lab technician will draw blood, usually from the arm, and test the blood to see how much thyroid stimulating hormone (TSH) is present. TSH controls the release of thyroid hormone and also controls the rate at which follicular cells grow. If these levels are abnormally high, it may suggest that the growth of cells is not being properly controlled. These cells may be cancer. The doctor may also have blood tests done to assess the presence of an altered RET gene or high levels of calcitonin and calcium. High levels of these substances may indicate the presence of cancer.
  
  
• Ultrasonography - An ultrasound is done by rubbing a wand attached to a machine over the area in question. The machine emits waves that produce a detailed picture of the inside of the body. The physician then uses the picture of the thyroid produced by the ultrasound to determine how many nodules are present, their size and whether they are filled with fluid or are solid. This procedure requires the patient to lie still while the machine takes pictures and is relatively painless.
  
  
• Radionuclide Scanning - A painless diagnostic procedure done to detect any change in your thyroid gland. A small amount of radioactive iodine (a tracer amount) is taken by mouth or injected into a vein. The radioactive iodine is absorbed by the thyroid gland. The nodule of the thyroid gland that absorb less radioactive material compared to the surrounding tissue are called cold nodules. The nodules that absorb more radioactive material than the surrounding tissue are called hot nodules and are usually benign. Most thyroid nodules appear on thyroid scans as cold nodules. Benign and cancerous nodules can appear as cold nodules and further testing will need to be done to determine if Thyroid Cancer is present. This test may be done if the results of the fine needle aspiration biopsy are inconclusive. Scans are also helpful for staging purposes in showing how far the Thyroid Cancer has spread.
  
  
• Biopsy - A small amount of tissue is surgically removed from the suspicious area and examined under a microscope by a pathologist for evidence of tissue alterations, cancer cells and other abnormalities.
  

STAGING OF THYROID CANCER:

Once the diagnosis of Thyroid Cancer is made, staging will need to be done so the Oncologist can determine the most appropriate treatment. Staging is used to describe how developed the cancer is. Staging is achieved through diagnostic tests such as magnetic resonance imaging (MRI), ultrasonography, computed tomography(CT) and whole body scan. The results of these diagnostic tests help the physician determine the size and location of the Thyroid Cancer and if the cancer has spread to other areas of the body. Papillary, follicular, and medullary thyroid cancer will be staged using staging categories I-IV, with I being the least advanced and IV the most severe. Anaplastic thyroid cancer does not have a staging system because it grows more quickly than other types of thyroid cancers.

Is it curable?

As with all cancers, the sooner thyroid cancer is detected, the better the chances of a cure.

• Thyroid cancer is one of the most curable of all cancers.
  
• Papillary and Follicular are the most common types of thyroid cancers and are also among the most easily cured. When treated appropriately, these types of cancer can have up to a 95% cure rate.
  
• Medullary thyroid cancer is more difficult to treat because it often involves the lymph nodes as well as the thyroid.
  
• Anaplastic thyroid cancer has a poor prognosis because it spreads very quickly and is difficult to control. Fortunately, this is also one of the more rare types of thyroid cancer.
  

It's easier to prevent cancer than to treat it....

Certain lifestyle and dietary habits may reduce your risk of developing Thyroid Cancer (as well as other cancers). Some of these include:

• Using iodized salt
  
• Not smoking
  
• Regular exercise
  
• Moderate, if any, consumption of alcohol
  
• Low fat, balanced diet
  

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