Signs and symptoms of thyroid cancer
Prompt attention to signs and symptoms is the best way to diagnose most thyroid cancers early. Thyroid cancer can cause any of the following signs or symptoms:
- A nodule, lump, or swelling in the neck, sometimes growing rapidly
- Pain in the front of the neck, sometimes going up to the ears
- Hoarseness or other voice changes that do not go away
- Trouble swallowing
- Breathing problems (feeling as if one were "breathing through a straw")
- A constant cough that is not due to a cold
If you have any of these signs or symptoms, talk to your doctor right away. Many non-cancerous conditions (and some other cancers of the neck area) can cause some of the same symptoms. Thyroid nodules are common and are usually benign. Still, if you have any of these problems, it's important to see your doctor right away so the cause can be found and treated, if needed.
Medical history and physical exam
If you have any signs or symptoms that suggest you might have thyroid cancer, your health care professional will want to get your complete medical history. You will be asked questions about your possible risk factors, symptoms, and any other health problems or concerns. If someone in your family has had thyroid cancer (especially medullary thyroid cancer) or tumors called pheochromocytomas, it is important to tell your doctor, as you might be at high risk for this disease.
A physical exam will give your doctor more information about possible signs of thyroid cancer and other health problems. During the exam, your doctor will pay special attention to the size and firmness of your thyroid and any enlarged lymph nodes in your neck.
Biopsy
The actual diagnosis of thyroid cancer is made from the results of a biopsy, in which cells from the suspicious area are removed and looked at under a microscope. The simplest way to find out if a thyroid lump or nodule is cancerous is with a fine needle aspiration (FNA) of the thyroid nodule.
This type of biopsy can usually be done in your doctor's office or clinic. Your doctor will place a thin, hollow needle directly into the nodule to take out (aspirate) cells and a few drops of fluid into a syringe. The doctor usually repeats this 2 or 3 times during the same appointment to take samples from several areas of the nodule. The cells can then be looked at under a microscope to see if they look cancerous or benign.
Before the biopsy, local anesthesia (numbing medicine) may be injected into the skin over the nodule, but in some cases an anesthetic may not be needed at all. A potential complication of the biopsy is prolonged bleeding, but this is rare except in people with bleeding disorders. Be sure to tell your doctor if you have a bleeding disorder.
This test is generally done on all thyroid nodules that are big enough to be felt. This means that they are larger than about 1 centimeter (about 1/2 inch) across. If a nodule is too small for the doctor to feel, sometimes FNA biopsies can be done using an ultrasound machine to help the doctor find the right place to put the needle.
About 2 tests in every 10 may need to be repeated because the sample ends up not containing enough cells. About 7 of 10 FNA biopsies will show that the nodule is benign. Cancer is clearly diagnosed in only about 1 of every 20 FNA biopsies.
Sometimes the test results come back as suspicious or atypical. This happens when the FNA findings can't show for sure if the nodule is benign or malignant. In these cases, a more involved biopsy may be needed to get a better sample, particularly if the doctor has reason to think the nodule may be cancerous. This might include a biopsy using a larger needle or a surgical "open" biopsy or a lobectomy (removal of half of the thyroid gland). Surgical biopsies are done in an operating room while you are under general anesthesia (in a deep sleep).
Imaging tests
Imaging tests may be done for a number of reasons, including to find out whether a suspicious area might be cancerous, to learn how far the cancer may have spread, and to help determine if treatment has been effective.
Chest x-ray
If you have been diagnosed with thyroid cancer, a plain x-ray of your chest may be done to see if cancer has spread to your lungs, especially if you have follicular thyroid cancer.
Ultrasound
Ultrasound, or sonography, uses sound waves to create images of your body. For this test, a small, microphone-like instrument called a transducer is placed on the skin in front of your thyroid gland. It gives off sound waves and picks up the echoes as they bounce off the thyroid. The echoes are converted by a computer into a black and white image on a computer screen. You are not exposed to radiation during this test.
This test is helpful in determining if a thyroid nodule is solid or filled with fluid. (Solid nodules are more likely to be cancerous.) It can also be used to check the number and size of thyroid nodules. Ultrasound features can sometimes suggest a nodule is likely to be a cancer, but ultrasound can't tell for sure.
For thyroid nodules that are too small to be felt, this test can be used to guide a biopsy needle into the nodule to obtain a sample. Even when a nodule is large enough to feel, some doctors prefer to use ultrasound to guide the needle.
Ultrasound can also help determine whether any nearby lymph nodes are enlarged because the thyroid cancer has spread. Many thyroid specialists recommend ultrasound for all patients with thyroid nodules large enough to be felt.
Computed tomography (CT) scan
The CT scan is an x-ray test that produces detailed cross-sectional images of your body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around you while you lie on a table. A computer then combines these pictures into images of slices of the part of your body being studied. Unlike a regular x-ray, a CT scan creates images of the soft tissues in the body.
You may be asked to drink a contrast solution or receive an IV (intravenous) line through which a different contrast dye is injected. This helps better outline structures in your body.
The injection may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if you have any allergies or have ever had a reaction to any contrast material used for x-rays.
CT scans take longer than regular x-rays. You need to lie still on a table while they are being done. During the test, the table slides in and out of the scanner, a ring-shaped machine that completely surrounds the table. You might feel a bit confined by the ring you have to lie in while the pictures are being taken. Spiral CT (also known as helical CT) is now used in many medical centers. This type of CT scan uses a faster machine that reduces the dose of radiation and yields more detailed pictures.
The CT scan can help determine the location and size of thyroid cancers and whether they have spread to nearby areas, although ultrasound is usually the test of choice. A CT scan can also be used to look for spread into distant organs such as the lungs.
In some cases, a CT scan can be used to guide a biopsy needle precisely into a suspected area of cancer spread. For a CT-guided needle biopsy, you remain on the CT scanning table, while the doctor advances a biopsy needle through the skin and toward the mass. CT scans are repeated until the doctor can see that the needle is within the mass. A biopsy sample is then removed and looked at under a microscope.
One problem with using CT scans for differentiated thyroid cancer is that the CT contrast dye contains iodine, which interferes with radioiodine scans (described below). For this reason, many doctors prefer MRI scans instead of CT scans.
Magnetic resonance imaging (MRI) scan
Like CT scans, MRI scans can be used to look for cancer in the thyroid, or cancer that has spread to nearby or distant parts of the body. But ultrasound is usually the first choice for looking at the thyroid. MRI can provide very detailed images of soft tissues such as the thyroid gland. MRI scans are also particularly helpful in looking at the brain and spinal cord.
MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body. A contrast material called gadolinium is often injected into a vein before the scan to better see details.
MRI scans are a little more uncomfortable than CT scans. First, they take longer — often up to an hour. Second, you have to lie inside a narrow tube, which is confining and can upset people with claustrophobia (a fear of enclosed spaces). Special, "open" MRI machines can sometimes be used instead. The machine also makes buzzing and clicking noises that you may find disturbing. Some centers provide earplugs to block this noise out.
Nuclear medicine scans
For nuclear medicine (radionuclide) scans, substances containing small amounts of radiation are put into the body. Special cameras are then used to detect where the substances go. These tests can help locate cells in the body that are not behaving normally, although they don't provide very detailed images.
Radioiodine scan: Radioiodine scans are often used in the care and management of patients with differentiated thyroid cancer (papillary, follicular, and Hurthle cell). Because medullary thyroid cancer cells do not take up iodine, radioiodine scans are not used for this cancer.
For this test, a small amount of radioactive iodine (called I-131) is swallowed (usually as a pill) or injected into a vein. Over time, the iodine is absorbed by the thyroid gland (or thyroid cells anywhere in the body) and a special camera is used several hours later to see where the radioactivity is.
For a thyroid scan, the camera is placed in front of your neck to measure the amount of radiation in the gland. Abnormal areas of the thyroid that contain less radioactivity than the surrounding tissue are called cold nodules, and areas that take up more radiation are called hot nodules. Hot nodules usually are not cancerous, but cold nodules can be either benign or cancerous. Because both benign and cancerous nodules can appear cold, this test by itself can't diagnose thyroid cancer.
If a biopsy has determined that a person has thyroid cancer, whole-body radioiodine scans are very useful to look for possible spread throughout the body from differentiated thyroid cancers. Scans after surgery can also help determine how far a thyroid cancer has spread, if at all.
If the entire thyroid gland has been removed because of cancer, radioiodine scans may be done frequently. The scan becomes more sensitive in this instance because more of the radioactive iodine is picked up by any thyroid cancer cells that might have spread elsewhere.
Radioiodine scans work best if patients have high blood levels of thyroid-stimulating hormone (TSH, or thyrotropin). When the thyroid has been removed, TSH levels may be increased by stopping thyroid hormone pills for a few weeks before the test. This lowers thyroid hormone levels and causes the pituitary gland to release more TSH, which in turn stimulates any thyroid cancer cells to take up the radioactive iodine. Although this intentional hypothyroidism is temporary, it can cause symptoms like tiredness, depression, weight gain, sleepiness, constipation, muscle aches, and reduced concentration. Another way to raise TSH levels before a scan is to give an injectable form of thyrotropin (Thyrogen®), which can make it unnecessary to withhold thyroid hormone for a long period of time.
Because iodine already in the body can interfere with this test, people are usually told not to ingest foods or medicines that contain iodine in the days before the scan.
Radioactive iodine can also be used to treat differentiated thyroid cancer, but it is given in much higher doses. This type of treatment is described in the section, "Radioactive iodine (radioiodine) therapy."
Positron emission tomography (PET) scan: For a PET scan, a radioactive substance (usually a type of sugar related to glucose, known as FDG) is injected into the blood. The amount of radioactivity used is very low. Because cancer cells in the body are growing quickly, they absorb large amounts of the radioactive sugar. A special camera can then create a picture of areas of radioactivity in the body.
This test can be very useful if your thyroid cancer is one that doesn't take up radioactive iodine. In this situation, the PET scan may be able to tell whether the cancer has spread.
PET scan images are not finely detailed like CT or MRI images, but a PET scan can look for possible areas of cancer spread in all areas of the body at once. Some newer machines are able to perform both a PET and CT scan at the same time (PET/CT scan). This lets the doctor see areas that "light up" on the PET scan in more detail.
Blood tests
No blood test can tell if a thyroid nodule is cancerous. But blood tests can help show if the thyroid is working normally, which may help the doctor decide what other tests may be needed.
Thyroid stimulating hormone (TSH)
Tests of blood levels of thyroid-stimulating hormone (TSH or thyrotropin) may be used to check the overall activity of your thyroid gland. Levels of TSH, which is made by the pituitary gland, may be high if the thyroid is not making enough hormones. This information can be used to help choose imaging tests (ultrasound or nuclear scans) for the initial evaluation of a thyroid nodule. The TSH level is usually normal in thyroid cancer.
T3 and T4 (thyroid hormones)
These are the main hormones made by the thyroid gland. Levels of these hormones may also be measured to get a sense of thyroid gland function. The T3 and T4 levels are usually normal in thyroid cancer.
Thyroglobulin
Thyroglobulin is a protein made by the thyroid gland. Measuring the thyroglobulin level in the blood cannot be used to diagnose thyroid cancer, but it can be helpful after treatment. A common way to treat thyroid cancer is to remove most of the thyroid by surgery and then use radioactive iodine to destroy any remaining thyroid cells. These treatments should lead to a very low level of thyroglobulin in the blood. If it is not low, this might mean that thyroid cancer is still present. If the level rises again after being low, it is a sign that the cancer may be coming back.
Calcitonin
Calcitonin is a hormone that helps regulate how the body uses calcium. It is made by C cells in the thyroid, the cells that can develop into medullary thyroid cancer (MTC). If MTC is suspected or if you have a family history of the disease, blood tests of calcitonin levels can help look for MTC. This test is also useful to look for the possible recurrence of MTC after treatment. Because calcitonin can affect blood calcium levels, these may be checked as well.
Carcinoembryonic antigen (CEA)
People with MTC often have high blood levels of a protein called carcinoembryonic antigen (CEA). Tests for CEA can sometimes help find this cancer.
Other blood tests
You may have other blood tests as well. For example, if you are scheduled for surgery, tests will be done to check your blood cell counts, to look for bleeding disorders, and to check the function of your liver and kidneys.
Other tests
Vocal cord exam (laryngoscopy)
Thyroid tumors can sometimes affect the vocal cords. If you are going to have surgery to treat thyroid cancer, a procedure called a laryngoscopy will likely be done beforehand to see if the vocal cords are moving normally. For this exam, the doctor looks at the larynx (voice box) with special mirrors or with a laryngoscope, a thin tube with a light and a lens on the end for viewing.
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