Thyroid cancer is a disease in which malignant (cancer) cells form in the tissues of the thyroid gland.
The thyroid is a gland at the base of the throat near the trachea (windpipe). It is shaped like a butterfly, with a right lobe and a left lobe. The isthmus, a thin piece of tissue, connects the two lobes. A healthy thyroid is a little larger than a quarter. It usually cannot be felt through the skin. The thyroid uses iodine, a mineral found in some foods and in iodized salt, to help make several hormones. Thyroid hormones do the following:
> Control heart rate, body temperature, and how quickly food is changed into energy (metabolism).
> Control the amount of calcium in the blood.
There are four main types of thyroid cancer:
> Papillary thyroid cancer: The most common type of thyroid cancer.
> Follicular thyroid cancer. Hürthle cell carcinoma is a form of follicular thyroid cancer and is treated the same way.
> Medullary thyroid cancer.
> Anaplastic thyroid cancer.
Signs and symptoms
Thyroid cancer may not cause early symptoms. It is sometimes found during a routine physical exam. Symptoms may occur as the tumor gets bigger. Other conditions may cause the same symptoms. A doctor should be consulted if any of the following problems occur:
> A lump in the neck.
> Trouble breathing.
> Trouble swallowing.
Medullary thyroid cancer is sometimes caused by a change in a gene that is passed from parent to child.
The genes in cells carry hereditary information from parent to child. A certain change in a gene that is passed from parent to child (inherited) may cause medullary thyroid cancer. A test has been developed that can find the changed gene before medullary thyroid cancer appears. The patient is tested first to see if he or she has the changed gene. If the patient has it, other family members may also be tested. Family members, including young children, who have the changed gene can decrease the chance of developing medullary thyroid cancer by having a thyroidectomy (surgery to remove the thyroid).
- Tests that examine the thyroid, neck, and blood are used to detect (find) and diagnose thyroid cancer.
The following tests and procedures may be used:
> Physical exam and history: An exam of the body to check general signs of health, including checking for signs of disease, such as lumps or swelling in the neck, voice box, and lymph nodes, and anything else that seems unusual. A history of the patient’s health habits and past illnesses and treatments will also be taken.
> Laryngoscopy: A procedure in which the doctor checks the larynx (voice box) with a mirror or with a laryngoscope. A laryngoscope is a thin, tube-like instrument with a light and a lens for viewing. A thyroid tumor may press on vocal cords. The laryngoscopy is done to see if the vocal cords are moving normally.
> Blood hormone studies: A procedure in which a blood sample is checked to measure the amounts of certain hormones released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it. The blood may be checked for abnormal levels of thyroid-stimulating hormone (TSH). TSH is made by the pituitary gland in the brain. It stimulates the release of thyroid hormone and controls how fast follicular thyroid cells grow. The blood may also be checked for high levels of the hormone calcitonin.
> Blood chemistry studies: A procedure in which a blood sample is checked to measure the amounts of certain substances, such as calcium, released into the blood by organs and tissues in the body. An unusual (higher or lower than normal) amount of a substance can be a sign of disease in the organ or tissue that makes it.
In stage I papillary and follicular thyroid cancer, the tumor is any size, may be in the thyroid, or may have spread to nearby tissues and lymph nodes. Cancer has not spread to other parts of the body.
In stage II papillary and follicular thyroid cancer, cancer has spread from the thyroid to other parts of the body, such as the lungs or bone.
In stage III papillary and follicular thyroid cancer, either of the following is found:
> the tumor is larger than 4 centimeters or the tumor is any size and cancer has spread to tissues just outside the thyroid, but not to lymph nodes; or
> the tumor is any size and cancer may have spread to tissues just outside the thyroid and has spread to lymph nodes near the trachea or the larynx (voice box).
Stage IV papillary and follicular thyroid cancer is divided into stages IVA, IVB, and IVC.
> In stage IVA, either of the following is found:
– the tumor is any size and cancer has spread outside the thyroid to tissues under the skin, the trachea, the esophagus, the larynx (voice box), and/or the recurrent laryngeal nerve (a nerve with two branches that go to the larynx); cancer may have spread to lymph nodes; or
– the tumor is any size and cancer may have spread to tissues just outside the thyroid. Cancer has spread to lymph nodes on one or both sides of the neck or between the lungs.
Surgery is the most common treatment of thyroid cancer. One of the following procedures may be used:
> Lobectomy: Removal of the lobe in which thyroid cancer is found. Biopsies of lymph nodes in the area may be done to see if they contain cancer.
> Near-total thyroidectomy: Removal of all but a very small part of the thyroid.
> Total thyroidectomy: Removal of the whole thyroid.
> Lymphadenectomy: Removal of lymph nodes in the neck that contain cancer.
Thyroid hormone therapy
Hormone therapy is a cancer treatment that removes hormones or blocks their action and stops cancer cells from growing. Hormones are substances made by glands in the body and circulated in the bloodstream. In the treatment of thyroid cancer, drugs may be given to prevent the body from making thyroid-stimulating hormone (TSH), a hormone that can increase the chance that thyroid cancer will grow or recur.
Radiation therapy is a cancer treatment that uses high-energy x-rays or other types of radiation to kill cancer cells or keep them from growing. There are two types of radiation therapy. External radiation therapy uses a machine outside the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly into the spinal column, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). Bladder cancer may be treated with intravesical (into the bladder through a tube inserted into the urethra) chemotherapy. The way the chemotherapy is given depends on the type and stage of the cancer being treated.