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How is thyroid cancer diagnosed?

If your doctor suspects you have thyroid cancer, they will feel your neck to check for any swelling or lumps. If you have a thyroid lump, your doctor may then perform one or more of the following tests to confirm whether the lump is cancerous.


A blood test cannot diagnose thyroid cancer, but you will have a blood test to check your levels of T3, T4 and thyroid-stimulating hormone (TSH). The thyroid generally functions normally even if thyroid cancer is present, and your hormone production won’t be affected. However, this blood test may rule out benign thyroid conditions, such as hypothyroidism or hyperthyroidism.

If your doctor suspects you may have medullary thyroid cancer, the levels of calcitonin in the blood may also be checked. High levels of calcitonin in the blood can be a sign of this type of thyroid cancer.

An ultrasound uses soundwaves to produce a picture of internal organs. If you have a lump in your thyroid the ultrasound can help the doctor determine whether it is a fluid-filled cyst or a solid thyroid nodule.

The doctor will also check if the nodule has characteristics that suggest cancer. The scan can also show if the lymph nodes (small, bean-shaped structures) in your neck are affected.

The ultrasound scan is painless and takes about 15 to 20 minutes. A gel is spread over your neck then a handheld device called a transducer is moved over the area. The device sends out soundwaves that echo when they meet something dense like an organ or tumour. A computer changes these echoes into a picture.

If the doctor feels a nodule in your neck or sees one during an ultrasound they may suggest a fine needle aspiration (FNA) biopsy.

During a FNA biopsy a thin needle is inserted into the nodule and a very small tissue sample is taken from the nodule for examination under a microscope. You may be given local anaesthesia (pain relief) to numb the area. Sometimes an ultrasound is used to guide the needle to the right spot. If not enough cells are removed the first time the process may be repeated.

If it’s not possible to determine the characteristics of the nodule with a FNA the doctor may remove part of the thyroid (hemi-thyroidectomy) to help confirm the diagnosis. If thyroid cancer is found after a hemi-thyroidectomy, you may need further surgery to remove the rest of your thyroid and possibly some lymph nodes in the neck. This will depend on the size and type of cancer, and if you have nodules in the other thyroid lobe.

The following scans are sometimes used to see if the cancer has spread to other parts of your body. This process is called staging and it will help your doctors to decide on the best treatment for you.

CT scan – A CT (computerised tomography) scan uses x-ray beams to create a detailed three-dimensional picture of the inside of the body.

PET scan – A PET (positron emission tomography) scan is rarely needed for thyroid cancer. However, it may be useful in some types of thyroid cancer, particularly if other tests give conflicting results.