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Thyroid cancer

Diagnosing thyroid cancer


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.

Blood test

While a blood test cannot diagnose thyroid cancer, it can 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.


The best way to get detailed information about your thyroid is with an ultrasound. This scan can show the size of any thyroid nodule and whether it is full of fluid or solid.

It can also show whether a nodule has any features that suggest it may be a thyroid cancer rather than a benign nodule, and whether the lymph nodes in the neck appear to be affected. An ultrasound is painless and takes about 15–20 minutes. 


If you have a thyroid nodule or enlarged lymph node in your neck, you may need a fine needle aspiration (FNA) biopsy.

This is an outpatient procedure that takes about 15–30 minutes. It involves a thin needle being inserted into the nodule to collect a sample of cells, which is examined by a pathologist to see whether it contains cancer cells.

If it is still unclear whether the nodule or enlarged lymph node is cancerous, you may need surgery to remove half of the thyroid, which will help confirm the diagnosis.

Additional scans

To see if the cancer has spread from the thyroid to other parts of your body, you may have a CT (computerised tomography) scan and/or a PET (positron emission tomography) scan. Some scans may be repeated after treatment to see how well the treatment has worked.

  • 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.
  • PET scan – you will be injected with a glucose solution to help cancer cells show up brighter on the scan. A PET 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.

Staging thyroid cancer

The tests described above help your specialist work out how far the cancer has spread. This is known as staging, and it helps your health care team recommend the best treatment for you. It is often not possible to precisely stage thyroid cancer until after surgery. 

The TNM (tumour−nodes−metastasis) staging system is often used for thyroid cancer. Each letter is assigned a number (and sometimes also a letter) to show how advanced the cancer is. Your doctor may also classify the cancer as low, intermediate or high risk. 


Prognosis means the expected outcome of a disease. You may wish to discuss your prognosis and treatment options with your doctor, but it is not possible for any person to predict the exact course of the disease. Instead, your doctor can give you an idea of what may happen, based on:

  • your test results
  • the type of thyroid cancer you have
  • the size of the tumour and how quickly it is growing
  • how well you respond to treatment
  • other factors such as your age, fitness and medical history.

The most common types of thyroid cancer (papillary and follicular) have an excellent long-term prognosis, especially if the cancer is found only in the thyroid or nearby lymph nodes in the neck. Even if the cancer has spread (metastasised), the outcome can still be good.

Doctors commonly use five-year survival rates as a way to discuss prognosis. This is because research studies often follow people for five years – it does not mean you will survive for only five years. Thyroid cancer has a very high five-year survival rate (97%).

Understanding Thyroid Cancer

Download our Understanding Thyroid Cancer booklet to learn more.

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Expert content reviewers:

A/Prof Diana Learoyd, Endocrinologist, Northern Cancer Institute, and Northern Clinical School, The University of Sydney, NSW; Dr Gabrielle Cehic, Nuclear Medicine Physician and Oncologist, South Australia Medical Imaging (SAMI), and Senior Staff Specialist, The Queen Elizabeth Hospital, SA; Dr Kiernan Hughes, Endocrinologist, Northern Endocrine and St Vincents Hospital, NSW; Yvonne King, 13 11 20 Consultant, Cancer Council NSW; Dr Christine Lai, Senior Consultant Surgeon, Breast and Endocrine Surgical Unit, The Queen Elizabeth Hospital, and Senior Lecturer, Discipline of Surgery, University of Adelaide, SA; A/Prof Nat Lenzo, Nuclear Physician and Specialist in Internal Medicine, Group Clinical Director, GenesisCare Theranostics, and The University of Western Australia, WA; Ilona Lillington, Clinical Nurse Consultant (Thyroid and Brachytherapy), Cancer Care Services, Royal Brisbane Women’s Hospital, QLD; Jonathan Park, Consumer.

Page last updated:

The information on this webpage was adapted from Understanding Thyroid Cancer - A guide for people with cancer, their families and friends (2020 edition). This webpage was last updated in July 2021. 

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