About half of all people develop a thyroid nodule by age 60. Most thyroid nodules cause no symptoms and are found during a routine physical exam or an imaging test for another health condition. NYU Langone doctors recommend annual thyroid examination, in which a general practitioner examines the neck for nodules.
There are several types of thyroid nodules. A nodule can be benign, or noncancerous; toxic, meaning it produces too much thyroxine; or cancerous. Doctors at NYU Langone are experts in determining what type you have and choosing the appropriate treatment.
About 90 to 95 percent of thyroid nodules are benign. Sometimes benign nodules, such as toxic nodules or toxic multinodular goiters, can cause the thyroid to produce excess amounts of thyroxine, a hormone that regulates the body’s metabolism. This results in a condition called hyperthyroidism, which causes a rapid heartbeat, an increased appetite, and weight loss.
Receiving radiation therapy to the head, neck, or chest during childhood increases a person’s risk for developing thyroid cancer. For this reason, childhood cancer survivors and those who were treated with radiation at a young age for enlargement of the thymus, an immune system gland; large tonsils; ringworm of the scalp; or acne are at increased risk of developing thyroid cancer.
Other risk factors for thyroid cancer include having a strong family history of thyroid cancer, such as a first-degree relative with the condition. Women are more likely than men to develop thyroid nodules and have nearly three times the odds of developing thyroid cancer. Most people with thyroid cancer are diagnosed between the ages of 20 and 55.
While thyroid cancer often does not cause symptoms, an enlarging growth may occasionally lead to neck swelling, pain, swallowing problems, shortness of breath, or voice changes.
To diagnose thyroid nodules or cancers, your doctor performs a physical exam, takes a medical history, and asks about your symptoms. Next, he or she may conduct several tests.
Doctors at NYU Langone were the first in the country to use ultrasound to identify thyroid nodules and determine whether they might be cancerous. Ultrasound uses sound waves to create images of the body on a computer monitor. Our doctors also use ultrasound to check lymph nodes in the neck, where some forms of thyroid cancer can spread.
NYU Langone doctors also helped to establish diagnostic criteria for benign and cancerous nodules. Features that may appear on an ultrasound that are associated with a higher-than-average risk of cancer include nodules that have an uneven border, are oblong instead of round, or have increased blood flow. Malignant, or cancerous, growths may contain areas that resemble very small calcium specks, which appear as bright spots on an ultrasound.
Ultrasound-Guided Fine Needle Aspiration Biopsy
Small nodules without suspicious features in people who don’t have risk factors for thyroid cancer may not require biopsy. The doctor simply monitors them, which is called watchful waiting.
If ultrasound reveals a thyroid nodule with suspicious features, doctors at NYU Langone may use ultrasound-guided fine needle aspiration to biopsy the nodule. To perform this type of biopsy, a doctor uses a tiny needle attached to a syringe to withdraw a small sample of thyroid tumor cells. He or she may also biopsy nearby lymph nodes to determine whether cancer has spread there. The doctor uses ultrasound imaging to guide the procedure.
The thyroid tumor sample is sent to a cytologist, a specialized pathologist who studies cells in a laboratory. He or she examines the thyroid nodule cells under a microscope to determine whether they are cancerous and, if they are, what type of cancer a person has.
Sometimes, the cytologist cannot tell for sure whether a thyroid tumor is cancerous. The results are considered indeterminate or suspicious and require further testing.
NYU Langone doctors offer sophisticated genetic testing to people with indeterminate biopsies. This testing enables doctors to assess the genetic makeup of a tumor and determine whether it is likely to be cancerous or benign.
Often, genetic tests can determine that cancer risk is low enough to avoid surgery. This is especially helpful when biopsied tissue does not conclusively show that a nodule is benign or malignant. These tests can also identify mutations that are associated with more aggressive cancer, which helps the surgeon plan the most effective surgery.
Radioactive Iodine Scan
If you have a benign thyroid nodule, doctors may use a radioactive iodine scan to determine whether it’s toxic. Toxic nodules produce too much thyroxine, putting you at risk for hyperthyroidism. This scan is usually performed after a blood test reveals that you have low levels of thyroid-stimulating hormone, which occurs in hyperthyroidism.
Before the scan, your doctor gives you a pill that contains a small amount of radioactive iodine. Because the thyroid absorbs iodine from the bloodstream, the radioactive iodine travels to the gland, highlighting its structure, including any nodules, during the scan.
Depending on your doctor’s preference, the radioactive iodine may be administered 4 to 24 hours before the test to give the thyroid time to absorb the material. During the scan, the doctor uses a special camera that detects the radioactive material in the thyroid.
The camera takes pictures of the thyroid from different angles to show the size, shape, and activity of the gland and any nodules. Bright spots on the scan, which indicate that radioactive iodine is more concentrated, show that a toxic nodule is present.
Nodules that do not cause the radioactive iodine to become concentrated are usually benign. However, because they are associated with thyroid cancer 5 to 10 percent of the time, the scan cannot provide a definitive diagnosis.
Blood tests cannot show whether a thyroid nodule is malignant or benign, but they can reveal how well the thyroid is functioning. These tests can also show whether a nodule is toxic or producing too much thyroxine, causing hyperthyroidism.
A doctor may want to measure levels of thyroid-stimulating hormone (TSH) in the blood. This hormone is released by the pituitary, a small gland at the base of the brain. TSH tells the thyroid to make thyroxine, which is necessary for many of the body’s functions. If the thyroid nodule is toxic, meaning it is producing too much thyroxine, levels of thyroid-stimulating hormone are often low.
If the nodule is toxic, the risk of cancer is very low and a biopsy may not be necessary. Thyroid cancers do not cause abnormal results on thyroid function tests.
Thyroxine and Triiodothyronine
Doctors may also measure levels of thyroid hormones—thyroxine, also known as T4, and triiodothyronine, known as T3. T4 is produced in the thyroid and is converted to T3 by the body. Small amounts of T3 are also directly produced by the thyroid gland itself. Levels that are too high or too low may be related to conditions called hyperthyroidism or hypothyroidism, respectively.
Levels of the hormone calcitonin, which helps control the body’s use of calcium, may be high in people with medullary thyroid cancer. If, based on your biopsy and family history, your NYU Langone doctor thinks you may have this form of thyroid cancer, he or she may order a blood test to check your calcitonin levels. This test may also be used after treatment to determine whether cancer has recurred.
People diagnosed with thyroid cancer rarely need additional imaging tests to determine whether the condition has spread to other parts of the body, such as the lungs, bone, or brain. Additional imaging is not typically used before treatment starts, but it may be helpful if doctors suspect cancer has recurred.
A CT scan uses X-rays and a computer to create three-dimensional, cross-sectional images of the body. Before the scan, your doctor may want to give you a contrast agent—a special dye that travels through the bloodstream—to enhance the images.
Because the contrast agent contains iodine, it can complicate the results of a radioactive iodine scan or treatment with radioactive iodine. Our endocrinologists, surgeons, radiologists, and nuclear physicians can discuss with you the benefits and drawbacks of a CT scan using the contrast agent.
An MRI scan is especially useful for creating images of the body’s soft tissues, including the brain, where thyroid cancer may spread—although it does so rarely. An MRI scan uses a magnetic field and radio waves to create computerized, three-dimensional images of structures in your body.
An important advantage of an MRI over a CT scan is that the MRI does not require iodine-containing contrast agents.
NYU Langone doctors may use a PET scan to search for cells that are very active. Such cells can signal infection, inflammation, or a variety of growths, and do not necessarily indicate thyroid cancer.
If thyroid cancer has been diagnosed, a PET scan can confirm whether it has spread to other organs. A PET scan can also help detect thyroid cancers that do not absorb radioactive iodine.
For example, this scan can be helpful in diagnosing rare, advanced papillary or follicular thyroid cancers. It can also help identify medullary or anaplastic thyroid cancers that have spread to nearby structures, such as the trachea or esophagus, the bloodstream, the lymph nodes, or distant organs.
A PET scan requires an injection of a small amount of radioactive glucose, or sugar, into a vein. This substance collects in tumor cells, which tend to process sugar more quickly than healthy tissues do. A computer then creates three-dimensional images of cancer activity in your body.
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