Thyroid cancer

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Overview

Thyroid cancer is the most common malignancy of the endocrine system, representing 3.8% of all new cancer cases in the United States and is the ninth most common cancer overall. The American Cancer Society estimates that 62,450 people in the United States will be diagnosed with thyroid cancer in 2015, and 1950 deaths will result from the disease.Over the past 3 decades, there has been a dramatic increase in the number of people diagnosed with thyroid cancer, which may be attributable to the wide use of imaging studies, including ultrasounds, computed tomography, magnetic resonance imaging, and positron emission tomography scans that incidentally detect thyroid nodules. Thyroid cancer is divided into several main types, with papillary thyroid cancer being the most common. The treatment options for patients with thyroid cancer include the surgical removal of the entire thyroid gland (total thyroidectomy), radioactive iodine therapy, and molecular-targeted therapies with tyrosine kinase inhibitors. This article summarizes the diagnosis and treatment of thyroid cancer, with recommendations from the American Thyroid Association regarding thyroid nodules and differentiated thyroid cancer. Recently approved drugs and treatment trends are also explored.

Symptoms

A lump (nodule) that can be felt through the skin on your neck.

A feeling that close-fitting shirt collars are becoming too tight.

Changes to your voice, including increasing hoarseness.

Difficulty swallowing.

Swollen lymph nodes in your neck.

Pain in your neck and throat.

Causes

Thyroid cancer happens when cells in the thyroid develop changes in their DNA. A cell's DNA contains the instructions that tell the cell what to do. The changes, which doctors call mutations, tell the cells to grow and multiply rapidly. The cells go on living when healthy cells would naturally die. The accumulating cells form a mass called a tumor.

The tumor can grow to invade nearby tissue and can spread (metastasize) to the lymph nodes in the neck. Sometimes the cancer cells can spread beyond the neck to the lungs, bones and other parts of the body.

For most thyroid cancers, it's not clear what causes the DNA changes that cause the cancer.

Types of thyroid cancer

Thyroid cancer is classified into types based on the kinds of cells found in the tumor. Your type is determined when a sample of tissue from your cancer is examined under a microscope. The type of thyroid cancer is considered in determining your treatment and prognosis.

Types of thyroid cancer include:

Differentiated thyroid cancers. This broad category includes types of thyroid cancer that start in the cells that produce and store thyroid hormones. These cells are called follicular cells. Differentiated thyroid cancers cells appear similar to healthy cells when viewed under a microscope.

Papillary thyroid cancer. This is the most common type of thyroid cancer. It can happen at any age, but it most often affects people ages 30 to 50. Most papillary thyroid cancers are small and respond well to treatment, even if the cancer cells spread to the lymph nodes in the neck. A small portion of papillary thyroid cancers are aggressive and may grow to involve structures in the neck or spread to other areas of the body.

Follicular thyroid cancer. This rare type of thyroid cancer usually affects people older than 50. Follicular thyroid cancer cells don't often spread to the lymph nodes in the neck. But some large and aggressive cancers may spread to other parts of the body. Follicular thyroid cancer most often spreads to the lungs and bones.

Hurthle cell thyroid cancer. This rare type of thyroid cancer was once considered a type of follicular thyroid cancer. Now it is considered its own type because the cancer cells behave differently and respond to different treatments. Hurthle cell thyroid cancers are aggressive and can grow to involve structures in the neck and spread to other parts of the body.

Poorly differentiated thyroid cancer. This rare type of thyroid cancer is more aggressive than other differentiated thyroid cancers and often doesn't respond to the usual treatments.

Anaplastic thyroid cancer. This rare type of thyroid cancer grows quickly and can be difficult to treat. However, treatments can help slow the progression of the disease. Anaplastic thyroid cancer tends to occur in people older than 60. It can cause severe signs and symptoms, such as neck swelling that worsens very quickly and may lead to difficulty breathing and swallowing.

Medullary thyroid cancer. This rare type of thyroid cancer begins in thyroid cells called C cells, which produce the hormone calcitonin. Elevated levels of calcitonin in the blood can indicate medullary thyroid cancer at a very early stage. Some medullary thyroid cancers are caused by a gene called RET that's passed from parents to children. Changes in the RET gene can cause familial medullary thyroid cancer and multiple endocrine neoplasia, type 2. Familial medullary thyroid cancer increases the risk of thyroid cancer. Multiple endocrine neoplasia, type 2, increases the risk of thyroid cancer, adrenal gland cancer and other types of cancers.

Other rare types. Other very rare types of cancer can start in the thyroid. These include thyroid lymphoma, which begins in the immune system cells of the thyroid, and thyroid sarcoma, which begins in the connective tissue cells of the thyroid.

Risk factors

Factors that may increase the risk of thyroid cancer include:


Female sex. Thyroid cancer occurs more often in women than in men. Experts think it may be related to the hormone estrogen. People who are assigned female sex at birth generally have higher levels of estrogen in their bodies.

Exposure to high levels of radiation. Radiation therapy treatments to the head and neck increase the risk of thyroid cancer.

Certain inherited genetic syndromes. Genetic syndromes that increase the risk of thyroid cancer include familial medullary thyroid cancer, multiple endocrine neoplasia, Cowden syndrome and familial adenomatous polyposis. Types of thyroid cancer that sometimes run in families include medullary thyroid cancer and papillary thyroid cancer.

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Complications

Possible Complications

Complications of thyroid cancer may include: Injury to the voice box and hoarseness after thyroid surgery. Low calcium level from accidental removal of the parathyroid glands during surgery. Spread of the cancer to the lungs, bones, or other parts of the body.

Prevention

Many people develop thyroid cancer for no known reason, so prevention isn’t really possible. But if you know you’re at risk for thyroid cancer, you may be able to take these steps:


Preventive (prophylactic) surgery: Genetic tests can determine if you carry an altered gene (a mutation) that increases your risk for medullary thyroid cancer or multiple endocrine neoplasia. If you have the faulty gene, you may opt to have preventive (prophylactic) surgery to remove your thyroid gland before cancer develops.

Potassium iodide: If you were exposed to radiation during a nuclear disaster, such as the 2011 incident at Fukushima, Japan, taking potassium iodide within 24 hours of exposure can lower your risk of eventually getting thyroid cancer. Potassium iodide (Pima®) blocks the thyroid gland from absorbing too much radioiodine. As a result, the gland stays healthy.