What is the thyroid gland? The thyroid is a small gland weighing less than one ounce that is located in the front of your neck. There are two lobes along the windpipe; these two lobes are joined by a narrow band of thyroid tissue called the isthmus. One of the major functions of the thyroid is to take the iodine in your body and convert it into thyroid hormones – important in the normal regulation of the metabolism of the body. Thyroid cells are the only cells in your body that can absorb and use iodine. Click here to learn more about how your thyroid works.
Thyroid cancer forms in the thyroid. It can occur at any age although it's more common after age 30. Typically, the older the patient, the more aggressive the cancer. About 35,000 new cases are found each year according to the National Cancer Institute, and women are more likely than men to have thyroid cancer by a ratio of three to one. Most thyroid cancers are found when patients or their primary physicians find a nodule in their thyroid, usually with no symptoms. Most thyroid nodules are benign, but it is important to exclude thyroid cancer in any clinical setting.
There are four types of thyroid cancer; these four types are determined by how the cancer cells look under a microscope:
- Papillary — This is the most common type of thyroid cancer, with a very high cure rate, very slow growth rate, and a ten year survival rate approaching 90% for the most favorable stages. Metastasis to the lymph nodes in the neck usually is present in about half the cases with small tumors, and in 75% of the cases with larger tumors. The presence of the cancer in the lymph nodes does cause a higher recurrence rate but it doesn't indicate a higher mortality rate. Lung and bone cancer are the two most common forms of distant metastasis – when the cancerous cells have spread beyond the immediate area of the thyroid gland. Distant metastasis is very uncommon. Peak onset for this type of thyroid cancer is age 30-50, with a 3 to 1 ratio of females to males (typically women of childbearing age). The overall cure rate is very high.
Learn more about papillary thyroid cancer.
- Follicular — This is the second most common form of thyroid cancer, accounting for about 10% of thyroid cancer cases. Like papillary thyroid cancer, it is very curable and treated in much the same way, with complete removal of the thyroid lobe with the malignant node and complete or partial removal of the unaffected lobe. Follicular thyroid cancer is considered more malignant than papillary thyroid cancer, and occurs in a slightly older age group (40-60). It's more likely to recur and spread than papillary thyroid cancer, but occurs only rarely after radiation therapy. Because vascular invasion and spread is more likely in follicular thyroid cancer, distant metastasis is more common. Lung, bone, brain, liver, bladder, and skin are typical potential sites for metastatic growth of follicular thyroid cancer. Conversely, lymph node involvement is generally far less than in papillary thyroid cancer.
Learn more about follicular thyroid cancer.
- Medullary — The third most common form of thyroid cancer, medullary carcinoma is a cancer of nonthyroid cells that release a hormone called calcitonin. These cells, called "C" cells, are normally present in the thyroid gland. Symptoms include a firm thyroid mass, goiter, diarrhea, cough, and/or cough with blood. Medullary cancer has a lower cure rate than the well-differentiated papillary and follicular thyroid cancers, but the cure rates are still much higher than for anaplastic thyroid cancer. Ten year survival rates are about 90% if the disease is confined to the thyroid, and about 70% if it has spread to the neck lymph nodes, and 20% when it has spread to distant sites. This form of the thyroid cancer tends to occur in families, and requires different treatment than other types of thyroid cancer.
Learn more about medullary thyroid cancer.
- Anaplastic — The least common thyroid cancer is the most deadly. Found in about .5% to 1.5% of people with thyroid cancer, it has a very low cure rate even with the very best of treatment. Only 10% of patients are alive three years after diagnosis; most patients do not live a year from date of diagnosis. Like papillary thyroid cancer, anaplastic thyroid cancer can arise many years after radiation exposure. Symptoms can include a lower neck mass that is enlarging, hoarseness or changing voice, cough, difficulty swallowing, loud breathing, and/or coughing up blood. Cervical lymph nodes are affected about 90% of the time at diagnosis. Anaplastic thyroid cancer is usually diagnosed when the patient or a family member notices a growing neck mass. These tumors are extremely fast-growing, and the patient will likely say they just noticed it, and it seems to be larger every day. These tumors invade adjacent as well as distant tissues and organs; at time of diagnosis, about 50% of patients will show metastasis to the lungs. Treatment is difficult; most of the cancers are so aggressively attached to vital neck structures that they are inoperable at time of diagnosis. Even with comprehensive and aggressive radiation, chemotherapy and surgical treatments, the survival rate at 3 years is less than 10%. Not all people who get anaplastic thyroid cancer will die but it is extremely important that this cancer be caught early and treated aggressively.
Learn more about anaplastic thyroid cancer.
Review Date: 3/28/2011
Reviewed By: The UT Health Science Center Surgical Oncology Faculty
Occasionally there are symptoms such as hoarseness, neck pain, or enlarged lymph nodes. Generally though, a thyroid nodule is found and will then be examined to determine if it is malignant. Most thyroid nodules are not malignant – these nodules are very common in adults, and the likelihood of having a thyroid nodule increases as we age. Again – very few of these nodules are malignant. Although symptoms can vary depending on the type of thyroid cancer, Typical symptoms include:
For more information on diagnostic tests, please visit the American Association of Endocrine Surgeons Patient Education site.
- Difficulty swallowing
- Enlargement of the thyroid gland
- Hoarseness or changing voice
- Neck swelling
- Thyroid lump (nodule)
Your physician will do a thorough physical exam. He will feel your thyroid for lumps (nodules) and will check your neck and nearby lymph nodes for growths or swelling. In addition to the physical, some or all of these tests may be done:
- Blood tests – Your doctor may check for abnormal levels of thyroid-stimulating hormone (TSH) in the blood. Too much or too little TSH means the thyroid is not working well. If your doctor thinks you may have medullary thyroid cancer, you may be checked for a high level of calcitonin and have other blood tests.
- Ultrasound – An ultrasound device aims sound waves at the thyroid, and a computer creates a picture of the waves that bounce off the thyroid. This picture can show nodules that are too small to be felt. Using the ultrasound image, the doctor can determine the size and shape of each nodule and whether the nodules are solid or filled with fluid. Nodules that are filled with fluid are usually not cancer. Nodules that are solid may be cancer.
- Thyroid scan – Your doctor may order a scan of your thyroid. You'll be asked to swallow a small amount of a radioactive substance. This will travel through your bloodstream. Thyroid cells that absorb the radioactive substance can then be seen on a scan. Nodules that take up more of the substance than the thyroid tissue around them are called "hot" nodules. Hot nodules are usually not cancer. Nodules that take up less substance than the thyroid tissue around them are called "cold" nodules, and these may be cancer.
- Biopsy – A biopsy is the only sure way to diagnose thyroid cancer. A pathologist checks a sample of tissue for cancer cells with a microscope. Your doctor may take tissue for a biopsy in one of two ways:
- Fine-needle aspiration – Most people have this type of biopsy. Your doctor removes a sample of tissue from a thyroid nodule with a thin needle. An ultrasound device helps the doctor see where to place the needle.
- Surgical biopsy – If a diagnosis can't be made from fine-needle aspiration, a surgeon removes the whole nodule during an operation. If the doctor suspects follicular thyroid cancer, surgical biopsy may be needed for diagnosis.
Treatment options vary depending on the type of thyroid cancer but, in general, surgery is usually the first treatment of choice with complete removal of the afflicted lobe as well as partial to complete removal of the second lobe of the thyroid. Radioactive iodine therapy is often used after surgery. An external beam of radiation can also be used in some situations. If the cancer has not responded to surgery or radiation, chemotherapy may be used but its effectiveness is limited, and only about a third of those treated with chemotherapy will show any improvement or benefit.
There is no known prevention for any of the types of thyroid cancer. Awareness of some risk factors, such as radiation therapy to the neck, can allow for earlier diagnosis and treatment.
Most thyroid cancers are very treatable and curable. The two most common types of thyroid cancer (papillary and follicular) are the most curable. In younger patients, the cure rate is better than 97% with appropriate treatment which usually consists of complete surgical removal of the lobe that contains the cancerous node, as well as partial or complete removal of the other thyroid lobe. Most thyroid cancers are papillary thyroid cancer – one of the most curable forms of cancer that humans get. The outlook for those diagnosed with medullary cancer is not quite so good, but still has about an 86% five year survival rate. Unfortunately, anaplastic thyroid cancer has a poor prognosis, with less than 5% of patients surviving five years; most do not survive longer than six months.