Thyroid cancer is a cancerous tumor or growth within the thyroid gland. Located under the thyroid cartilage (Adam’s apple) in the front section of the neck, the thyroid gland is part of the endocrine system, a network of glands that produce and secrete hormones. It is responsible for absorbing iodine from food, water and the blood and using the iodine to produce thyroid hormones. Thyroid hormones play a major role in regulating the body’s metabolism, the body’s process of using food for energy and growth.

The thyroid gland is located just underneath the skin. As a result, tumors can often be felt as bumps in the neck (thyroid nodules). According to the American Cancer Society (ACS), one-third of all people develop thyroid nodules. These nodules can be either benign (noncancerous) or malignant (cancerous). In some situations, the nodules remain undiscovered and never cause a problem. It is estimated that 95 percent of thyroid nodules are benign.

Thyroid nodules can occur at any age, but are most common in adults. Approximately 5 to 10 percent of thyroid nodules are malignant. The four main types of malignant thyroid tumors include:

• Papillary carcinoma
• Follicular carcinoma
• Anaplastic carcinoma
• Medullary thyroid carcinoma (MTC)

Tumors can be found in normal-sized thyroid glands and enlarged thyroid glands. Currently physicians do not know what causes the development of benign thyroid nodules.

The exact cause of most thyroid cancers is also unknown. Some forms of cancer are caused by DNA mutations that “turn on” oncogenes (genes that speed up cell division) or “turn off” tumor suppressor genes (genes that slow down cell division or cause cells to die at the right time). In people with thyroid cancer, these mutations can be inherited or acquired during a lifetime.

Although there is no single cause of thyroid cancer, researchers have identified a number of factors that appear to place a person at higher risk for developing the disease. These risk factors include having had an enlarged thyroid and having a family history of thyroid disease.

Symptoms of thyroid cancer include a lump, neck pain and hoarseness. Individuals who experience these symptoms are encouraged to contact their physician to determine the cause. If a physician suspects thyroid cancer, a biopsy may be performed to remove a small sample of tissue and examine it under a microscope for the presence of abnormal cells.

If cancer is diagnosed from the biopsy, the disease will be staged to determine a course of treatment.

The lower the stage, the earlier the disease has been identified and the better the prognosis for recovery. The main method used to treat thyroid cancer is surgery. In some cases, a diagnosis is not made until after a thyroid nodule is removed during surgery.