June 15, 2024
This page was reviewed under our medical and editorial policy by Sasan Fazeli, M.D., assistant clinical professor in the Department of Diabetes, Endocrinology and Metabolism, and Karen Tsai, M.D., assistant clinical professor in the Department of Diabetes, Endocrinology and Metabolism, City of Hope® Cancer Center Duarte.
If thyroid cancer is suspected, doctors will order certain imaging, blood tests or procedures to diagnose it and learn more about it. These tests help doctors confirm the type of thyroid cancer, its location and its stage.
A thyroid nodule biopsy is usually how thyroid cancer is confirmed and diagnosed. Other imaging and blood tests might be recommended during the diagnosis and staging process to detect nodules and give doctors more information about the cancer, such as the tumor’s size, where it is located, whether any lymph nodes are involved and if cancer has spread.
To diagnose thyroid cancer, doctors test a sample of thyroid tissue from the suspicious lump or nodule. To obtain this tissue, doctors perform a biopsy. There are different types of biopsies, but the main one used to confirm thyroid cancer is fine needle aspiration (FNA), also called fine needle biopsy, which uses a thin needle and syringe to obtain a small sample of fluid and tissue from a tumor.
If the neck has swollen lymph nodes and the doctor suspects they are cancerous, a fine needle aspiration may be used to test lymph node tissue. The tissue samples are then sent to the pathology lab, where it’s examined under the microscope for the presence of cancerous cells.
Doctors will typically take a sample from every concerning thyroid nodule or lymph node and will typically use ultrasound to position the needle and remove the tissue sample. Doctors may numb the area before the procedure by injecting local anesthesia under the skin.
A fine needle aspiration biopsy is done at a doctor’s office and it rarely causes bleeding, unless a person is taking blood thinners or has a high risk of bleeding. Sometimes, though, it might yield an indeterminate finding, meaning it was not clear whether or not the sample was cancerous.
A fine needle aspiration and biopsy may also be used to perform a molecular and genetic analysis test, which may help to further characterize the risk of thyroid cancer.
There are also three other types of biopsies, listed below, which may be done to get additional tissue samples.
Core biopsy: A doctor uses a slightly larger needle to withdraw a cylindrical sample or core from the nodule. Local anesthesia is typically used for a core biopsy, but it is not considered a surgical procedure.
Surgical biopsy: This procedure removes the entire nodule.
Surgical lobectomy: A surgeon removes part of the thyroid gland.
Both surgical biopsy of the nodule and lobectomy are performed under general anesthesia by a surgeon and may require an overnight hospital stay.
If a biopsy is not conclusive, additional molecular testing may be performed to gauge thyroid cancer risk and evaluate for genetic changes in the thyroid tissue. Doctors may look particularly for changes in specific genes, like BRAF or RET/PTC, which may mean the tissue is cancerous. Identifying genetic changes may also give doctors information on treatments that may be most appropriate.
Several types of imaging tests may be used to help diagnose, locate and monitor thyroid cancer during and after treatment. These tests may also be used during the staging process because they provide information about the tumor size and lymph node involvement, and whether or not the cancer has spread outside of the neck.
Ultrasound imaging uses sound waves to produce detailed pictures of internal organs without radiation exposure. A doctor or technician moves a wand called a transducer over the skin of the area, and sound waves generate an image showing the thyroid gland.
From this image, doctors distinguish the number of nodules present, their size and their characteristics. This is especially helpful when diagnosing cancer, as solid nodules are more likely to be cancerous. An ultrasound may also show if nearby lymph nodes are enlarged or appear concerning, signaling that cancer may have spread. Doctors may also use an ultrasound to help guide the needle placement during a diagnostic biopsy.
A radioiodine scan, or whole-body scan, uses a small amount of radioactive iodine as a tracer. For this procedure, patients swallow a radioactive iodine pill, which comes in capsule form. Thyroid cells absorb the tracer, which makes them visible on the resulting image. Hot nodules, areas with more radioactivity, are unlikely to be cancerous. Cold nodules have less radioactivity and may be more likely to be cancerous.
This scan does not diagnose cancer, but it may help doctors understand more about the characteristics of thyroid nodules. Radioiodine scans are also used to determine whether cancer has spread in patients who have differentiated thyroid cancer, a slow-growing type of thyroid cancer that includes papillary thyroid cancer, follicular thyroid cancer or oncocytic (Hürthle cell) thyroid cancer. For this reason, it’s used after a total thyroidectomy. It is also used to see if cancer has spread after surgery to treat thyroid cancer with a larger dose of radioactive iodine, or other treatment modalities.
A CT scan, short for computed tomography, uses X-rays captured from different angles to generate a 3D image of the body’s interior. These images, which are also called CAT scans, are combined to create a cross-sectional view that allows doctors to distinguish abnormal tissue or tumors. CT scans may show a tumor’s size and may involve using a contrast dye to get clearer images.
CT scans may be used to capture cross-sectional images of neck areas that ultrasounds are unable to see. They may also be performed to determine whether cancer has spread to the chest or abdomen. For people with hereditary medullary thyroid cancer, who are more likely to develop additional growths in the abdomen, CT scans may be used to monitor for the presence of tumors or tumor growth.
Magnetic resonance imaging (MRI) creates cross-sectional images of the inside of the body using powerful magnets instead of radiation. MRI captures images from various angles. It is used to create clear images of soft tissue areas that may be hard to see in other imaging tests.
Doctors use MRIs to look for cancer that has spread to other areas of the body, like the brain and spinal cord. While an MRI is also able to create clear images of the thyroid, since it is made of soft tissue, an ultrasound is typically performed first.
Positron emission tomography (PET) scans create images of organs and tissues and show areas of increased cell activity. A small injection of radioactive sugar is absorbed by cells, such as cancer cells, that use a lot of energy. The scan provides a picture of areas where cells are more active, possibly fast-growing, meaning they may be cancerous. Sometimes PET scans are combined with CT scans. The resulting PET/CT scan provides a more detailed image than a PET scan alone.
Some thyroid cancers do not absorb radioactive iodine, while others do. Doctors commonly use PET scans to monitor the spread of cancers that do not take up radioactive iodine.
During a laryngoscopy, a doctor examines the larynx (voice box), vocal cords and nearby areas. For the examination, a doctor inserts a long, thin instrument called a laryngoscope through the nose or mouth and down into the throat. The scope has a light and lens or camera on the end.
Sometimes, the doctor may instead use a brightly lit headlamp and a special mirror to look down the throat as part of the examination.
A laryngoscopy may be performed before or after thyroid surgery to check how the vocal cords are functioning. It may also be done after thyroid cancer is diagnosed to determine whether the tumor is crowding or affecting the vocal cords.
Doctors use several kinds of blood tests throughout thyroid cancer diagnosis, treatment and monitoring, though none may actually diagnose thyroid cancer. These blood tests are used to monitor thyroid function, rule out or check for other conditions, determine whether treatment is working, evaluate whether cancer has come back after treatment and if the cancer is progressing.
Thyroid-stimulating hormone (TSH), also called thyrotropin, is made by the pituitary gland in the brain. If the thyroid is not making enough hormones, the pituitary gland may produce more TSH, causing levels to rise.
TSH levels tend to be normal in people with thyroid cancer, so a TSH test may help doctors rule out other thyroid function abnormalities.
Similar to TSH, levels of the two main thyroid hormones, triiodothyronine (T3) and thyroxine (T4), are often normal when thyroid cancer is present. This blood test checks the levels of T3 and T4 in the blood so doctors may rule out other thyroid function abnormalities and learn more about how the thyroid is functioning.
The thyroid gland makes a protein called thyroglobulin (Tg). Tg is also made by differentiated thyroid cancer cells. Monitoring thyroglobulin levels before, during and after treatment helps doctors understand how the treatment is working and whether the cancer has returned.
After thyroid cancer surgery and/or radioactive iodine therapy, the goal is for the patient to have very low Tg levels because treatment eliminates the thyroid cells that produce it. If a Tg test shows high or rising levels of the protein, it may mean that there are thyroid cancer cells still present or that cancer has returned. Thyroglobulin antibodies (TgAb) are also concurrently tested with Tg levels, as high antibody levels can interfere with Tg level measurements. In addition, TgAb, in conjunction with Tg levels, can be helpful in monitoring patients’ treatment response and whether the cancer has returned.
Calcitonin, a hormone that helps regulate calcium use throughout the body, is made by C cells in the thyroid gland. These cells may transform to medullary thyroid cancer. Doctors use calcitonin blood levels to screen for this cancer if it is suspected or a family member has been diagnosed with the disease. Calcitonin tests are also performed to determine the treatment response and whether cancer has recurred after treatment.
A CEA test checks the level of a protein called carcinoembryonic antigen (CEA). CEA is often high in people with medullary thyroid cancer, so doctors may use a CEA test as one way to monitor treatment response in medullary thyroid cancer.
Thyroid cancer staging varies by the tumor type. For papillary or follicular tumor types, staging also differs according to age, with separate stage criteria for those under age 55 and those age 55 and older.
Thyroid cancer staging uses the American Joint Committee on Cancer (AJCC) TNM system. TNM stands for tumor, nodes and metastasis. Doctors use these letters, along with numbers or additional letters to describe other details, to refer to different characteristics of the cancer.
Tumor: Doctors will look at the size of the cancer tumor and determine whether it has spread into or has affected nearby tissue. The descriptors T0, T1, T2, T3 and T4 are used to represent the location and size of the tumor. For thyroid cancer, additional letters may be added to T to describe a solitary tumor (s), more than one tumor (m) or a tumor that cannot be evaluated (X).
Nodes: This refers to lymph nodes, part of the body’s immune system. Assessing what lymph nodes are involved is a key aspect of staging thyroid cancer because the head and neck have many of them, called regional lymph nodes. The descriptors N0, N1, N1a and N1b are used to represent the specific areas of lymph nodes that are involved. NX is used to describe cancer where it is not clear which, if any, lymph nodes are involved.
Metastasis: Checking for metastasis (spread) lets doctors see if the cancer has spread away from the head and neck into distant areas of the body. M0 means that cancer has not spread to other parts of the body, and M1 means that it has. MX is used to describe cancer where it is not clear if cancer has spread or where.
Thyroid cancer staging may be complex, and it is OK to ask questions. The more that is known about the type of cancer and where it has spread, the more tailored treatment options may be.
Thyroid cancer has four staging groups, varying by tumor type and sometimes the patient’s age:
Stage 1: The tumor may be of any size and may have extended to surrounding tissues and lymph nodes, but it has not reached other body parts.
Stage 2: The tumor may be of any size, and has possibly spread to nearby tissues and lymph nodes. Additionally, cancer has progressed beyond the thyroid to distant areas like the lungs or bones.
Stage 1: Cancer is limited to the thyroid, and the tumor measures 4 centimeters or less.
Stage 2: Cancer has one of three sets of characteristics.
Stage 3: The tumor has grown beyond the thyroid, reaching soft tissues under the skin, the esophagus, the trachea, the larynx or the recurrent laryngeal nerve. It may also have spread to lymph nodes.
Stage 4: Stage 4 is divided into Stages 4A and 4B.
Stage 1: Cancer is confined to the thyroid, with the tumor measuring 2 centimeters or less.
Stage 2: Cancer is either confined to the thyroid with a tumor larger than 2 centimeters, or a tumor of any size has spread to nearby neck muscles.
Stage 3: The cancer is of any size and may have spread to nearby neck muscles. Lymph nodes on one or both sides of the trachea or larynx are involved.
Stage 4: Stage 4 is divided into Stages 4A, 4B and 4C. In all of these stages, the tumor may be of any size.
Anaplastic thyroid cancer, a group of cancer types that are fast growing and spread quickly, is always considered Stage 4.
Stage 4A: Cancer is confined to the thyroid gland, and the tumor may be of any size.
Stage 4B: Cancer has one of three sets of characteristics.
Stage 4C: The tumor may be of any size, and cancer has spread to parts of the body beyond the thyroid and neck, with potential lymph node involvement.
Tests for thyroid cancer. American Cancer Society, May 12, 2020.
https://www.cancer.org/cancer/types/thyroid-cancer/detection-diagnosis-staging/how-diagnosed.html
Thyroid cancer: diagnosis. American Society of Clinical Oncology, September, 2023.
https://www.cancer.net/cancer-types/thyroid-cancer/diagnosis
How is a biopsy done? American Cancer Society, August 1, 2023.
https://www.cancer.org/cancer/diagnosis-staging/tests/biopsy-and-cytology-tests/biopsy-types.html
Thyroid cancer treatment (PDQ®) – patient version. National Cancer Institute, July 21, 2023.
https://www.cancer.gov/types/thyroid/patient/thyroid-treatment-pdq
X-rays and other radiographic tests for cancer. American Cancer Society, November 30, 2015.
https://www.cancer.org/cancer/diagnosis-staging/tests/imaging-tests/x-rays-and-other-radiographic-tests.html
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