Thyroid Cancer Uncommon, Often Highly Treatable

Occasionally, lumps or nodules develop on the thyroid gland. Sometimes these nodules can be felt in a physical examination, and patients may be referred to an endocrinologist - a physician specializing in the study of glands, hormones and their disorders - for further diagnosis and treatment.

Thyroid nodules are malignant in only about one case in 20, according to the American Cancer Society, which describes thyroid cancer as one of the most treatable cancers, with a five-year survival rate of 97%. There are at least four types of thyroid cancer, according to the National Cancer Institute (NCI), but in the United States, two types account for up to 95% of all cases. These are papillary thyroid cancer, which makes up about 80% of cases; and follicular thyroid cancer, which accounts for about 15%.

"Thyroid cancer is relatively uncommon," says Gilbert Fareau, MD, Medical College of Wisconsin Assistant Professor of Endocrinology, Metabolism and Clinical Nutrition. "Like other thyroid disorders, it's more common among women. However, thyroid cancer only ranks eighth among cancers in women," with far fewer cases than more common cancers like breast, colon, lung and others.

Thyroid cancer affects women about three times more often than men, and it tends to affect people at a younger age than many other cancers.

Thyroid Cancer Symptoms
According to NCI, thyroid cancer often does not have symptoms in its early stages. But as the cancer grows, symptoms may include:

• A lump in the front of the neck
• Hoarseness or voice changes
• Swollen lymph nodes in the neck
• Trouble swallowing or breathing
• Pain in the throat or neck that does not go away

"Most often, these symptoms are not due to cancer," NCI notes, adding: "An infection, a benign goiter or another health problem is usually the cause." However, anyone whose symptoms persist for a couple of weeks should see a doctor to be diagnosed and treated as early as possible, Dr. Fareau says.

"Nodules are often picked up incidentally during a physical exam. Sometimes patients themselves feel a neck mass, or a family member might notice it." If a suspicious mass is detected during a physical exam, the physician might also check for growths or swelling in nearby lymph glands.

Diagnosis
"Typically, with a nodule, we get an ultrasound of the thyroid," Dr. Fareau says, and if the nodule is large or suspicious in appearance, we might also do a biopsy of the tissue."

NCI describes two types of biopsies:

• Fine-needle aspiration - Guided by ultrasound, the doctor removes a sample of tissue from a thyroid nodule with a thin needle. This is the most common type of thyroid biopsy.
• Surgical biopsy - If a diagnosis cannot be made from the fine-needle aspiration, a surgeon removes the nodule surgically. If the cancer is the follicular type, the diagnosis might require a surgical biopsy.

Other diagnostic options might involve a blood test for abnormal levels of thyroid-stimulating hormone (TSH) or another hormone, calcitonin. In some cases, a scan might be ordered, requiring a patient to swallow a small amount of a radioactive substance to differentiate the nodule type.

Treatment
Typically, thyroid cancers are treated by removing all or most of the thyroid gland surgically, followed by a single treatment of radioactive iodine. "Patients with papillary and follicular cancers are treated similarly," Dr. Fareau says. "Then they undergo lifelong surveillance, because thyroid cancer can be indolent. Unlike cancers that can recur within five years, thyroid cancer can recur 10 years after the diagnosis or even later. The first year after the initial treatment, patients undergo a whole body scan. After that, we typically repeat neck ultrasounds and monitor a tumor marker called thyroglobulin."

Rarer Types of Thyroid Cancer
Two other types of thyroid cancer are medullary thyroid cancer, which accounts for 4% or fewer cases; and anaplastic, which represents 1% or less. Anaplastic cancer is fast-growing, aggressive and difficult to control; it tends to occur in older patients, Dr. Fareau says. Medullary thyroid cancer tends to grow slowly. It can be easier to control if found and treated before it spreads to other parts of the body. It can be hereditary, he notes.

Who's at Risk?
"The vast majority of thyroid cancer patients have no risk factors," says Dr. Fareau, "although a history of exposure to radiation or radiation therapy involving the neck can play a role." Before joining the Medical College, he completed a Clinical and Research Fellowship in Endocrinology at the Baylor College of Medicine and the University of Texas MD Anderson Cancer Center joint program, where his educational interests included diagnostic and treatment strategies of endocrine cancers.

Under risk factors, NCI describes how some older patients may have been exposed to excessive radiation from X-rays, which years ago were improperly used to treat enlarged tonsils, acne and other conditions around the head and neck. It notes that the levels of radiation in routine medical and dental X-rays today are low, and their benefits exceed any risk. It does suggest, however, that patients ask doctors and dentists about using shields to protect other parts of the body, especially if they have been exposed to repeated X-rays.

Obviously, patients who were exposed to greater amounts of radiation from atomic weapons or from nuclear power plant accidents may have an increased risk of thyroid diseases.

"Thyroid cancer is still fairly uncommon," Dr. Fareau notes, "and many cases are highly treatable. Research continues to discover more about the causes and treatments."

Barbara Abel
HealthLink Contributing Writer

Gilbert Fareau, MD, practices at the Froedtert & Medical College of Wisconsin Endocrinology, Metabolism and Clinical Nutrition Clinic.

For more information on this topic, see the HealthLink article Thyroid: When the Body's Regulator Goes Wrong.

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.