Thyroid cancer refers to cancers that start in the thyroid gland, a butterfly-shaped organ under the Adam's apple, in the front part of the neck. The thyroid has several different types of cells and performs several different tasks, including regulating metabolism and calcium usage. Different cancers can emerge from the different types of cells in the thyroid. It is important to know which type of cell is implicated in order to determine the severity of the cancer and the best treatment.
The two most common types of malignant thyroid cancers are papillary carcinoma and follicular carcinoma. Papillary carcinoma, comprises about 80 percent of thyroid cancers. Follicular carcinoma — which arises from the cells that regulate metabolism — comprises about 13 percent of all thyroid cancers. Rarer forms of thyroid cancer are medullary thyroid carcinoma, anaplastic carcinoma, thyroid lymphoma, and thyroid sarcoma.
Nearly two thirds of thyroid cancers are found in people between the ages of 20 and 55, making it one of the earliest-onset cancers. The death rate from thyroid cancer is low, as most thyroid cancers are slow-growing and treatable.
Although scientists have not discovered the precise causes of thyroid cancers, there are strong correlations with certain risk factors.
The most significant risk factor for thyroid cancer is exposure to radiation. Having had head or neck radiation treatments as a child increases the risk of cancer. A diet low in iodine has also been identified as a risk factor. Most Americans consume enough iodine by eating iodized salt. However, in some other parts of the world, thyroid cancer caused by low iodine is more common. Some of the rarer thyroid cancers are linked to certain inherited medical conditions, such as an abnormal gene, familial adenomatous polyposis ("FAP"), Cowden disease, and Carney complex, type 1. Lastly, three times as many women as men develop thyroid cancer, and usually at a younger average age.
Although some thyroid cancers produce no symptoms, in most cases one or more of the following symptoms will be present: a lump, nodule, or swelling in the neck; pain in the front of the neck, sometimes radiating up to the ears; persistent hoarseness or voice changes; trouble swallowing or breathing; and a constant cough not due to a cold or bronchial irritation. It is important to note that these symptoms most often indicate non-cancerous conditions of the thyroid, but should always be examined by a physician.
Most cases of thyroid cancer present no risk factors, so the disease is nearly impossible to prevent. In persons with genetic mutations linked to thyroid cancer, prophylactic removal of the thyroid gland has proven effective in avoiding cancer.
On a positive note, most thyroid cancers can be cured by prompt diagnosis and a combination of treatments (this varies on the type of cancer, its stage of development, and the patient's condition). The five-year survival rate for all types of thyroid cancer patients diagnosed at Stage I is close to 100 percent; at Stage II, over 98 percent. Typical treatments include surgery and radioactive iodine. Other therapy such as chemotherapy, and external beam radiation therapy may sometimes be used.