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Thyroid nodules

  • Lumps or bumps in the thyroid gland are called thyroid nodules. Most thyroid nodules are benign, but about five to ten percent are cancerous. Sometimes these nodules make too much thyroid hormone and cause hyperthyroidism. Nodules that produce too much thyroid hormone are almost always benign.
  • People can develop thyroid nodules at any age, but they occur most commonly in older adults. Fewer than 1 in 10 adults have thyroid nodules that a doctor can feel. But when the thyroid is looked at with an ultrasound, many more people are found to have nodules that are too small to feel and most of them are benign.
  • Most nodules are cysts filled with fluid or a stored form of thyroid hormone called colloid. Solid nodules have little fluid or colloid and are more likely to be cancerous. Still, most solid nodules are not cancer. Some types of solid nodules, such as hyperplastic nodules and adenomas, have too many cells, but the cells are not cancer cells.
  • Benign thyroid nodules sometimes can be left alone (not treated) and watched closely as long as they’re not growing or causing symptoms. Others may require some form of treatment.
 
 

Thyroid Cancer

  • Thyroid cancer is a type of cancer that starts in the thyroid gland. Cancer starts when cells begin to grow out of control. 
  • Where thyroid cancer starts
  • The thyroid gland is in the front part of the neck, below the thyroid cartilage (Adam’s apple). In most people, the thyroid cannot be seen or felt. It is shaped like a butterfly, with 2 lobes — the right lobe and the left lobe — joined by a narrow piece of gland called the isthmus.
  • The thyroid gland has 2 main types of cells:
  • Follicular cells use iodine from the blood to make thyroid hormones, which help regulate a person’s metabolism. Having too much thyroid hormone (hyperthyroidism) can cause a fast or irregular heartbeat, trouble sleeping, nervousness, hunger, weight loss, and a feeling of being too warm. Having too little hormone (hypothyroidism) causes a person to slow down, feel tired, and gain weight. The amount of thyroid hormone released by the thyroid is regulated by the pituitary gland at the base of the brain, which makes a substance called thyroid-stimulating hormone (TSH).
  • C cells (also called parafollicular cells) make calcitonin, a hormone that helps control how the body uses calcium.
  • Other, less common cells in the thyroid gland include immune system cells (lymphocytes) and supportive (stromal) cells. Different cancers develop from each kind of cell. The differences are important because they affect how serious the cancer is and what type of treatment is needed.
  • Many types of growths and tumors can develop in the thyroid gland. Most of these are benign (non-cancerous) but others are malignant (cancerous), which means they can spread into nearby tissues and to other parts of the body.

Types of Thyroid Cancers

  • The main types of thyroid cancer are:
  • Differentiated (including papillary, follicular, and Hürthle cell)
  • Medullary
  • Anaplastic (an aggressive cancer)
  • Differentiated thyroid cancers
  • Most thyroid cancers are differentiated cancers. The cells in these cancers look a lot like normal thyroid tissue when seen in the lab. These cancers develop from thyroid follicular cells.
  • Papillary cancer (also called papillary carcinomas or papillary adenocarcinomas): About 8 out of 10 thyroid cancers are papillary cancers. These cancers tend to grow very slowly and usually develop in only one lobe of the thyroid gland. Even though they grow slowly, papillary cancers often spread to the lymph nodes in the neck. Even when these cancers have spread to the lymph nodes, they can often be treated successfully and are rarely fatal.
  • There are several subtypes of papillary cancers. Of these, the follicular subtype (also called mixed papillary-follicular variant) is the most common. It has the same good outlook (prognosis) as the standard type of papillary cancer when found early, and they are treated the same way. Other subtypes of papillary carcinoma (columnar, tall cell, insular, and diffuse sclerosing) are not as common and tend to grow and spread more quickly.
  • Follicular cancer (also called follicular carcinoma or follicular adenocarcinoma): Follicular cancer is the next most common type, making up about 1 out of 10 thyroid cancers. It is more common in countries where people don’t get enough iodine in their diet. These cancers usually do not spread to lymph nodes, but they can spread to other parts of the body, such as the lungs or bones. The outlook (prognosis) for follicular cancer is not quite as good as that of papillary cancer, although it is still very good in most cases.
  • Hürthle (Hurthle) cell cancer (also called oxyphil cell carcinoma): About 3% of thyroid cancers are this type. It is harder to find and to treat.
  • Medullary thyroid carcinoma
  • Medullary thyroid cancer (MTC) accounts for about 4% of thyroid cancers. It develops from the C cells of the thyroid gland, which normally make calcitonin, a hormone that helps control the amount of calcium in blood. Sometimes this cancer can spread to lymph nodes, the lungs, or the liver even before a thyroid nodule is discovered.
  • This type of thyroid cancer is more difficult to find and treat, There are 2 types of MTC:
  • Sporadic MTC, which accounts for about 8 out of 10 cases of MTC, is not inherited (meaning it does not run in families). It occurs mostly in older adults and often affects only one thyroid lobe.
  • Familial MTC is inherited and 20% to 25% can occur in each generation of a family. These cancers often develop during childhood or early adulthood and can spread early. Patients usually have cancer in several areas of both lobes. Familial MTC is often linked with an increased risk of other types of tumors. 
  • Anaplastic (undifferentiated) thyroid cancer
  • Anaplastic carcinoma (also called undifferentiated carcinoma) is a rare form of thyroid cancer, making up about 2% of all thyroid cancers. It is thought to sometimes develop from an existing papillary or follicular cancer. This cancer is called undifferentiated because the cancer cells do not look very much like normal thyroid cells. This cancer often spreads quickly into the neck and to other parts of the body and is very hard to treat.

Less Common Thyroid Cancers

  • Less than 4% of cancers found in the thyroid are thyroid lymphomas, thyroid sarcomas, or other rare tumors.
  • Parathyroid cancer
  • Behind, but attached to, the thyroid gland is 4 tiny glands called parathyroids. The parathyroid glands help regulate the body’s calcium levels. Cancers of the parathyroid glands are very rare — there are probably fewer than 100 cases each year in the United States.
  • Parathyroid cancers are often found because they cause high blood calcium levels. This makes a person tired, weak, and drowsy. It can also make you urinate (pee) a lot, causing dehydration, which can make the weakness and drowsiness worse. Other symptoms include bone pain and fractures, pain from kidney stones, depression, and constipation.
  • Larger parathyroid cancers may also be found as a nodule near the thyroid. No matter how large the nodule is, the only treatment is to remove it surgically. Parathyroid cancer is much harder to cure than thyroid cancer.