Thyroid function tests (TFTs): this test checks the level of thyroid hormones in the blood. It is usually requested whenever someone first presents to their doctor with a thyroid swelling. It is a helpful test to see if the thyroid gland is working normally. This test is usually normal if thyroid cancer is present.
Calcitonin: this test can help diagnose medullary thyroid cancer as there is a high level of this hormone in the blood in this disease. This test is not helpful for other types of thyroid cancer and is not usually done until after the tests mentioned below.
Fine needle aspiration cytology (FNAC)
This involves a small needle being inserted through the skin into the thyroid gland lump or into lymph glands/nodes in the neck to remove some cells. This can either be done in the routine clinic or may be done with the help of an ultrasound scan.
The sample of cells is then looked at with a microscope to see if there are any signs of thyroid cancer present.
The test is most useful when cancer cells can be seen. If the test does not show any cancer cells, this does not necessarily mean cancer is not present, as not all types of cancer can be diagnosed with this test. Follicular thyroid cancer cannot be diagnosed by FNAC in which case a diagnostic thyroid lobectomy (removal of the abnormal lobe) will need to be performed so that the whole thyroid nodule can be examined in the laboratory in order to reach a diagnosis.
This test may need to be repeated if the first sample is not helpful. The test may also be negative if the needle does not pick up any cancer cells.
Sometimes a FNAC result will not be helpful and a core biopsy or very occasionally a surgical biopsy may be needed. If this is needed the doctor would explain in more detail what it would entail and whether any anaesthetic is required.
Thyroid Ultrasound scan (USS)
This test uses gel and a probe rubbed over the neck to look at the size and texture of the thyroid gland and the lymph glands/nodes in the neck. It can show if there are any lumps in the thyroid gland, if the lumps are solid or fluid containing and if the lymph glands/nodes look normal in shape and size. If anything shows up it is possible to use the ultrasound probe and pictures to guide the needle used for a FNA (see above).