Diagnosis & staging
Diagnosis
These are tests that may be used to diagnose this type of cancer.
- Thyroid cancers are often found during a regular physical check-up.
- People with enlarged thyroid should have thyroid function blood tests and an ultrasound scan.
- Fine needle aspiration biopsy (FNA) may provide the diagnosis.
- A thyroid scan using a radioactive iodine tracer is sometimes helpful.
For more information tests used to diagnose cancer, see our
Recommended Websites, Diagnostic Tests section.
Types and stages
Types
There are 4 main types of thyroid tumours, based on how the cancer cells look under a microscope:
Papillary carcinoma
- This is the most common form in Canada - over 80% of thyroid cancers diagnosed are papillary.
- It is slow-growing. Patients have excellent survival if diagnosed early.
- It is usually found in only one of the lobes.
Follicular carcinoma
- This is the second most common type of thyroid cancer.
- It arises from follicular cells which are responsible for producing thyroid hormones.
- It is slow-growing. Patients have excellent survival if diagnosed early.
- It is often treated with radioactive iodine since this tumour is most likely to capture radioactive iodine.
Medullary carcinoma
- It arises from C-cells which produce the hormone calcitonin.
- It is slow-growing. Patients have good survival if diagnosed early.
- It may spread to the lymph glands or to other sites in the body.
- It usually only occurs on one side of the thyroid.
Anaplastic carcinoma
- This is the least common type of thyroid cancer.
- It occurs more often in middle aged and elderly people.
- It is the most aggressive type of thyroid cancer. It is fast-growing with early spread.
- It may be too advanced at the time of diagnosis to remove surgically.
- It is often treated with radiation therapy alone.
- This type of cancer is rarely cured.
Stages
Staging describes the extent of a cancer. The TNM classification system is used as the standard around the world. In general a lower number in each category means a better prognosis. The stage of the cancer is used to plan the treatment.
T describes the site and size of the main tumour (primary)
N describes involvement of lymph nodes
M relates to whether the cancer has spread (presence or absence of distant metastases)
Stage I
Confined to the thyroid
Stage II
Involving regional lymph nodes
Stage III
Locally invasive
Stage IV
Distant metastases