The thyroid gland is located in the lower front of the neck, below the voice box (larynx) located in the upper part of the neck, and above the collarbones. Thyroid cancer (carcinoma) usually appears as a painless lump in this area. In most cases, the lump affects only one side, and the results of thyroid function tests (blood tests) are usually normal.
Over 35,000 new cases of thyroid cancer are expected in the United States every year. Women are two to three times more likely to have thyroid cancer than men. Thyroid cancer is most common after 30, but can develop at any age.
Many patients with thyroid cancer have no symptoms whatsoever. A lump on the thyroid gland may be found by chance on a routine physical exam or an imaging study of the neck done for unrelated reasons. Other patients feel a gradually enlarging lump in the front portion of the neck or have difficulty swallowing or speaking. Occasionally, the lump may cause a feeling of pressure or shortness of breath. Finding a lump in the neck should be brought to the attention of your physician, even in the absence of symptoms.
Causes and Risk Factors
The exact reason nodules grow in the thyroid gland is not known. But these factors increase the risk:
- Family History. If a parent or sibling had a thyroid nodule, the chance of developing a nodule is increased
- Age. The risk of developing a nodule increases as you age.
- Gender. Woman develop nodules more often than men
- Thyroiditis. Nodules are more likely to form in people who have chronic inflammation of the thyroid gland.
- Radiation exposure to the head or neck. Babies, children and teenagers were treated with radiation for birthmarks, acne or enlarged tonsils in the 1940s and 1950s. People who had these treatments have an increased risk. Exposure to nuclear power plant accidents (for example, the 1986 nuclear power plant explosion in Cherynobyl), or radioactive particles released into the air during atomic weapons testing also increases the risk.
Thyroid Cancer Types
- Papillary thyroid cancers account for about 80 to 90 percent of all cases.
- Papillary tumors develop more often during 30 to 60 years of age.
- They occur three times more often in women than in men.
- The cure rate is usually 97 percent or better.
- Papillary tumors often spread to lymph nodes in the neck (about 25 percent of the time), but rarely spread to distant organs.
- Distant metastases to lung, bones and other sites are rare (<3 percent at time of initial diagnosis).
Follicular Thyroid Carcinoma (including Hurthle Cell Carcinoma)
- Follicular thyroid cancers are the second most common thyroid cancer, comprising about 15 percent of total cases.
- Follicular thyroid cancers usually develop during 40-60 years of age.
- They occur three times more often in women than men.
- The cure rate is typically 90 percent or better.
- Metastasis to the lymph nodes is less common than in papillary cancers
- Metastasis to distant organs (for example. lungs, bones, brain, or liver) is more common than with papillary carcinoma.
- Medullary thyroid cancers are a rare type of thyroid cancer and accounts for about three to five percent of all thyroid cancer cases.
- It occurs more often in older adults.
- Metastasis to the lymph nodes is common at the time of diagnosis.
- Prognosis varies depending on extent of disease at time of diagnosis and post-operative calcitonin levels.
- Anaplastic tumors are the least common type of thyroid cancer, making up only one percent of all thyroid cancer cases.
- The tumors grow rapidly, are difficult to treat and the cure rate is very low.
- The average age of onset is 65 years of age and older.
- Men are two times more likely than women to have anaplastic cancer.
- The prognosis is generally poor due to the aggressive nature of these cancers.
A combination of symptoms, medical history, physical exams and tests are used to determine a diagnosis. Thyroid nodules are often found during a routine physical examination. Your doctor might feel an abnormal lump on the front of your neck.
The TSH blood test measures a pituitary gland hormone that stimulates the thyroid gland. If the TSH level is increased, the thyroid gland may not be functioning properly. Additional blood tests are needed to measure other thyroid hormones. Both pituitary and thyroid tests are required to confirm that the problem is located in the thyroid gland. Click here for more information on blood work for thyroid diagnostics.
Thyroid ultrasound uses painless sound waves to create an image of the thyroid gland and identify nodules. Ultrasound can show if a nodule is solid or a fluid-filled cyst, but it cannot determine if a nodule is benign or malignant.
Ultrasound Guided Fine Needle Aspiration Biopsy
Fine Needle Aspiration Biopsy (FNA). A needle is placed into the thyroid nodule, the cells are aspirated, and then examined under a microscope to determine if a nodule is cancerous.
The most important treatment for thyroid cancer is to completely remove the tumor along with the remaining thyroid gland (total thyroidectomy). Surgeons at the Thyroid Cancer Program are experts in the treatment of thyroid tumors. Using this type of therapy, the majority of cancers will be either cured or controlled and less than 20 percent will show progression. Most of the time, residual cancer can be treated with additional surgery or radioactive iodine. For resistant tumors, external beam radiation may be prescribed or the patient may be entered into a clinical trial with newer therapies or receive some existing targeted chemotherapies. Fortunately, most patients have an excellent prognosis when treated early by experienced physicians.
Radioactive iodine treatment has been prescribed for over 50 years and is often used to destroy residual thyroid tissue as well as any thyroid cancer that is remaining. It may be administered by swallowing a capsule after an individual has been off their thyroid hormone for a number of weeks (endogenous withdrawal protocol) or following two injections of thyrogen while the patient remains on thyroid hormone. The patient must be on a low-iodine diet for two weeks before the therapy and are usually hospitalized for two days in isolation in order to avoid environmental contamination with radioactivity. Two days after the radioactive iodine is given, thyroid hormone therapy is resumed if the patient has stopped their thyroid hormone. A full body scan is done at two days and seven days following the therapeutic doses of radioactive iodine in order to detect residual thyroid tissue. Since surgery removes the vast majority of thyroid tissue, much of the radioiodine will not be absorbed and will leave the body primarily through the urine. Small amounts will also be excreted in saliva, sweat, tears, vaginal secretions, and feces. Nearly all the radioactive iodine will leave the body during the first two days after the dose has been given.
Side effects are minimal and typically transient. The most common side effects include decreased taste, nausea, inflammation of the salivary glands or dry eyes. Nuclear medicine staff and your endocrinologist will provide you with more information should this be part of your thyroid cancer treatment.
External Beam Radiation
External beam radiation uses radioactivity from a high energy X-ray machine to destroy cancer cells. Malignant cells receive a high dose of radiation for approximately five minutes, during a six- to eight-week course of treatment. Side effects are fatigue, redness in the treated area, hoarseness or difficulty swallowing.
Unlike other cancers, traditional chemotherapy has not been shown to be beneficial in the treatment of thyroid cancer. For thyroid cancers that have become resistant to radioactive iodine or which continue to progress despite surgery and/or external beam radiation, a number of new medications that target the biochemical abnormalities in thyroid cancer are available. Although none of these therapies are currently approved by the Food and Drug Administration for the treatment of thyroid cancer, a number of clinical studies have shown that they are reasonably effective in halting the progression of the tumor. As part of the Southern California Thyroid Cancer Consortium, Cedars-Sinai Thyroid Cancer Program physicians are well versed in the administration of targeted therapies and are kept abreast of current clinical trials on the west coast.
Following surgery or other treatments, regular follow-up visits with an endocrinologist are very important to check for the return of cancer to the thyroid or the spread of cancer cells to other organs in the body. Monitoring of thyroglobulin levels with periodic blood tests is key to proper treatment. Consistently high levels of thyroglobulin can signal a return of the cancer. Depending on the size of the tumor, the rate of growth or how close it is to other organs, a physician may recommend further imaging diagnostics and treatment. Thyroid cancer can recur as late as 20 or 30 years after the original diagnosis or treatment, although if a patient remains cancer free for five years, the recurrence rate decreases.