Thyroid Cancer

What is thyroid cancer?

Sometimes thyroid tissue begins to grow uncontrollably, causing one or more nodules to form. The reason why this happens is unknown. Cancer (malignancy) is the biggest concern when nodules form. Cancerous nodules 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.

There are four types of thyroid cancer.
Papillary thyroid cancer. This is the most common type of cancer. Over 70 percent of thyroid cancers are papillary. This cancer is usually not fast growing and does not spread quickly into surrounding tissue.
Follicular thyroid cancer. This type makes up 10 to 15 percent of thyroid cancers. Follicular cancer can travel through the bloodstream and into other areas of the body, such as the lungs or bone.
Medullary thyroid cancer. This type accounts for 4 percent of thyroid cancers. It is more likely to develop if there is a family history of this type of cancer.
Anaplastic thyroid cancer. This type is rare, accounting for about 2 percent of thyroid cancers. Anaplastic cancer is a fast growing cancer, spreading quickly into surrounding tissue. Treatment is the least effective in this type of cancer.

What are the risk factors for thyroid cancer?

Gender. Women are about three times more likely than men to develop thyroid cancer.
Age. In women, thyroid cancer is usually diagnosed in their 40s and 50s. Men are usually diagnosed in their 60s and 70s.
Family history or genetic makeup. Thyroid cancer can sometimes run in families. Inheriting an abnormal gene can increase the risk of developing medullary thyroid cancer.
Exposure to radiation. A history of radiation treatments to the head and neck, especially treatments that were given during childhood. Exposure to radiation can also come from fallout from a nuclear power plant accident. Tests that use radiation to make a medical diagnosis – such as dental x-rays or mammograms -- do not cause thyroid cancer.
History of goiter. Goiter is an enlargement of the thyroid gland.
Iodine deficiency. Iodine is necessary to produce thyroid hormone production. Thyroid cancer is more common in parts of the world where there is a lack of iodine in the diet, such as central Asia and central Africa. In the US, iodine is present in table salt and other foods, lowering the risk of thyroid cancer.
What are the symptoms of thyroid cancer?
In most cases, no signs or symptoms are seen 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:

Lump in the neck
Pain in the lower front part of the neck
Trouble breathing
Trouble swallowing
Swollen lymph nodes, especially in the neck

How is thyroid cancer diagnosed?

Fine Needle Aspiration

One or more of the following tests help to determine if cancer is present.

Physical exam. A physical exam can check for lumps or swelling in the neck, enlargement of the thyroid (goitre), and general health.
Blood tests. Blood tests check for levels of hormones released by other organs in the body. An elevated level of one hormone in particular, calcitonin, is a sign of thyroid cancer.
Thyroid scan. With this scan, a special camera and radioactive iodine (given as a pill), produce an image of the thyroid on a computer screen. This test is not ordered frequently since it is only useful in certain circumstances.
Other scans/imaging tests (CT scan, radio-iodine scan, PET scan, MRI). These tests use various methods to determine location, size, and spread of thyroid cancer. Methods include x-rays, injection of dyes or radioactive substances in a vein, radio waves, and a magnet.
Fine-needle aspiration (FNA) biopsy. During this procedure, a thin needle is inserted through the skin and into the thyroid gland and/or nodules. A sample of cells is removed and checked for cancer.
Ultrasound of the thyroid. This test determines the size of the lump on the thyroid. It is also used to guide a FNA biopsy.
Surgical biopsy. Since individual nodules cannot be removed, this involves taking out either one thyroid lobe (one side) or the whole thyroid.
Genetic testing.

How is thyroid cancer treated?

You may hear your surgeon talk about the ‘stage’ of thyroid cancer. This is a classification system that determines the size of the tumour, if it has spread within the thyroid gland, or how much the cancer has spread to other areas of the body. The lower the stage (the stages are 0 through IV), the less the cancer has spread. Treatment plans are developed based on the stage and the type of cancer.

Stage I and II papillary and follicular thyroid cancer
Treatment options include:

Surgery to remove the entire 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. This option is used only when the tumour is very small (less than 10 mm -- which is less than one-third of an inch) stage I cancers.
Stage III and IV papillary and follicular thyroid cancer
Treatment options include:

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
Hormone therapy
Clinical trial of chemotherapy or of targeted therapy
Medullary thyroid cancer:
Treatment options include:

Total thyroidectomy for tumours only in the thyroid, with removal of lymph nodes in the neck that contain cancer
For tumours that recur (come back) in the thyroid, radiation therapy given as a palliative treatment (given 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
Targeted therapy for cancer that has spread to other areas of the body
Anaplastic thyroid cancer
There is no staging system for anaplastic cancer. It is considered to be stage IV thyroid cancer. This type of thyroid cancer grows faster than the other types.

Treatment options include:

Surgery to create an opening in the windpipe, for tumours that block the airway. This surgery is called a tracheostomy.
Total thyroidectomy to reduce symptoms only if the tumour is in the area of the thyroid
External-beam radiation therapy
Clinical trials of chemotherapy and radiation therapy following thyroidectomy
Clinical trials studying new methods of treatment of thyroid cancer
Thyroid cancer that recurs
Treatment options include:

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
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. The 5-year survival rates for people with papillary and follicular thyroid cancers exceed 90 percent. The 5-year survival rate for people with medullary thyroid cancer is about 86 percent; 10-year survival rate is about 65 percent. The 5-year survival rate for people with anaplastic thyroid cancer is about 7 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. Changes in specific genes can occur in members of the same family. These gene changes are associated with an increased risk of thyroid cancer. A person might choose having his/her currently cancer-free thyroid totally removed to prevent cancer from developing there.
Taking potassium iodide tablets after exposure to large amounts of radiation. Potassium iodide protects the thyroid gland from iodine 131, though not from other radioactive material. People who have multinodular goitre, 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 the 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.