Tests for thyroid cancer
If thyroid cancer is suspected, your doctor may order a number of tests. You may not have all of the tests described in this section, depending on your particular circumstances.
A blood test cannot diagnose thyroid cancer, but it may help rule out other conditions, such as hypothyroidism or hyperthyroidism. Your levels of T3, T4 and thyroid-stimulating hormone (TSH) are usually checked first. But because the thyroid may still work normally with cancer, hormone levels are not always affected.
If your doctor suspects you may have medullary thyroid cancer, they may check your calcitonin levels. High levels of calcitonin in the blood can be a sign of this type of thyroid cancer.
The best way to get detailed information about your thyroid is with an ultrasound. This scan can show the size of any thyroid lump (nodule) and whether it is solid, cystic (full of fluid) or a mix of both.
An ultrasound can also show other signs that suggest thyroid cancer, and if the lymph nodes in the neck look like they have been affected.
The nodule will usually be rated as high or low risk, based on its size and appearance. This will help the doctors decide whether you should have a biopsy.
Fine needle aspiration
If you have a thyroid nodule or an enlarged lymph node in your neck, you may need a fine needle aspiration (FNA) biopsy, also sometimes called a fine needle biopsy. This is done as an outpatient, sometimes during the ultrasound appointment, and takes about 15–30 minutes.
If you are having an FNA biopsy:
- the area may be numbed with a local anaesthetic, the needle may be uncomfortable, but isn’t usually very painful and is over quickly
- a thin needle is inserted into the nodule or node to collect some cells
- ultrasound may be used to guide the needle to the right spot
- the biopsy sample is sent to a laboratory, and a specialist doctor called a pathologist examines it under a microscope to see whether the sample contains cancer cells.
If your doctor can’t tell whether the nodule or lymph node is cancerous, you may have more scans or surgery to remove thyroid tissue to test (partial thyroidectomy). This will usually confirm the diagnosis. Some thyroid nodules are difficult to biopsy because of where they are located. In this case you may also need a surgical biopsy. It can be difficult to tell if follicular tumours are cancerous from an FNA – so they may also need a surgical biopsy.
Also called molecular or genomic tests, genetic tests look for changes (mutations) in the genes. These changes are in the tumour cells. They are not usually needed for thyroid cancer and aren’t covered by Medicare. Genetic testing (on DNA from the blood) may be used in very rare cases of medullary thyroid cancer.
Genetic tests from a FNA are sent overseas and can cost over $2100. They may give a better indication that cancer is unlikely, and avoid unnecessary surgery. In rare cases, genetic tests may be done on tissue (removed during surgery) for certain cancers that are likely to need targeted therapy. These tests are done in Australia and the cost varies.
Other imaging scans
To see if the cancer has spread from the thyroid to other parts of your body, some people may have a CT (computerised tomography) scan or a PET (positron emission tomography) scan. This process is called staging. These scans may be done before or after any initial treatment, or at a later time to see how well treatment is working (see Follow-up appointments).
A CT scan uses x-rays and a computer to create a detailed picture of an area inside the body. You may need a CT scan if your thyroid is very enlarged, if it extends below the collarbone, or if your doctor suspects that the cancer has spread to other areas in the neck.
Before the scan, a special dye known as contrast may be injected into one of your veins. This helps ensure that anything unusual can be seen more clearly on the pictures. The dye may make you feel flushed or hot, and it may produce a strange taste in your mouth for a few minutes.
The CT scanner is a large, doughnut-shaped machine. You lie on a table that moves in and out of the scanner. You will be asked to remain still and hold your breath for a few seconds during the scan. It may take 30–60 minutes to prepare, but the scan itself takes only a few minutes.
A PET-CT scan is sometimes used if other tests are unclear or if thyroid cancer has come back (recurred). To prepare for the PET scan, you will be asked not to eat or drink for a period of time (fast). Before the scan, you will be injected with a glucose solution containing a small amount of radioactive material. Cancer cells show up brighter on the scan because they take up more of the glucose solution than normal cells do.
You will be asked to sit quietly for 30–90 minutes while the glucose solution moves around your body. You will then have a scan of your entire body to locate any cancer cells. The scan takes about 30 minutes.
Full body scan
After RAI treatment you usually have a full body scan to see if any thyroid or cancer cells remain in the body. This is one way your doctor can stage thyroid cancer and see if it is likely to come back (recur). It is usually only used for people who have RAI treatment.
Before having scans, tell the doctor if you have any allergies or have had a reaction to contrast during previous scans.
You should also let them know if you have diabetes or kidney disease or are pregnant or breastfeeding.
Podcast: Tests and Cancer
A/Prof Diana Learoyd, Endocrinologist, GenesisCare North Shore, Faculty of Medicine and Health, University of Sydney, NSW; Emeritus Professor Leigh Delbridge AM, The University of Sydney, Thyroid Surgeon, The Mater and North Shore Private Hospitals, NSW; Prof Ruta Gupta, Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital and The University of Sydney, NSW; Susan Leonard, Cancer Nurse Coordinator Thyroid and Brachytherapy, Cancer Care Services, Royal Brisbane and Women’s Hospital, QLD; Dr Dean Lisewski, Endocrine and General Surgeon, Fiona Stanley Hospital and St John of God Hospital, Murdoch, WA; Caitriona Nienaber, 13 11 20 Consultant, Cancer Council WA; Jonathan Park, Consumer; A/Prof David Pattison, Deputy Director and Senior Staff Specialist, Department of Nuclear Medicine and Specialised PET Services, Royal Brisbane and Women’s Hospital and School of Medicine, University of Queensland, QLD; Prof Bruce Robinson, Endocrinologist, Co-Head, Cancer Genetics, Kolling Institute of Medical Research, The University of Sydney and Royal North Shore Hospital, NSW; Marissa Ryan, Team Leader (Cancer) Pharmacist, Princess Alexandra Hospital, Brisbane, QLD.
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