There are a number of tests your doctor may use to diagnose papillary thyroid cancer (also known as papillary thyroid carcinoma). This article explains the most common diagnostic tests for thyroid cancer—fine needle aspiration biopsy, ultrasound, and blood tests.
Fine Needle Aspiration Biopsy
As with all forms of cancer, thyroid cancer is diagnosed from the results of a biopsy. To determine if a thyroid nodule is cancerous, doctors use a fine needle aspiration biopsy (FNA). This is usually the first test doctors will use if they suspect thyroid cancer—and in some cases, it may be the only test used.
In an FNA biopsy, a doctor inserts a thin, hollow needle into the thyroid tissues and removes a sample of cells. Your doctor may repeat this a few times to retrieve samples from different parts of the swollen nodule. The extracted cells are then examined under a microscope to determine if they are benign or cancerous. This is generally done under ultrasound guidance for preciseness and to ensure that enough cells are extracted for the pathologists to make a judgment.
To get more details about FNA, read our article about fine needle aspiration biopsy.
Your doctor may order imaging tests to better view the thyroid. Arguably the most common imaging test for thyroid cancer is an ultrasound. An ultrasound uses sound waves to create an image of the thyroid. A small, hand-held instrument is placed on the skin over the thyroid and transmits the sound waves and produces an image.
An ultrasound shows whether the thyroid nodule is fluid-filled or solid (solid nodules are more likely to be cancerous). Plus, it highlights all the thyroid nodules and nearby lymph nodes. Another benefit of ultrasound is that it helps doctors accurately guide the needle when they perform a fine needle aspiration biopsy.
This diagnostic test is safe, quick, and painless. But ultrasound alone cannot definitively show whether a thyroid nodule is cancerous. However, ultrasound can show certain features that suggest a nodule is likely to be cancerous. In these cases, a FNA biopsy is usually performed to confirm the findings.
To learn more about this diagnostic test, read our article about thyroid nodule ultrasound.
Your doctor may also order a CT scan after your thyroid cancer is confirmed if there is suggestion that the cancer may be extending outside the thyroid in certain ways. CT scans are not frequently ordered at the time of thyroid cancer diagnosis unless there are indications, such as the need to see the relationship between the cancer and the esophagus (feeding tube) and the trachea (air pipe).
Though blood tests alone can't diagnose papillary thyroid cancer, they can determine if you have healthy levels of thyroid-stimulating hormone (TSH). This information will help your doctor understand how well your thyroid gland is functioning overall. If it is found to be over-functioning (hyperthyroid), then this has implications for further work-up with a thyroid nuclear scan and for medical treatment.
Before the routine use of ultrasound in evaluating thyroid nodules, patients would get nuclear scans. These scans would characterize thyroid nodules as cold or hot.
Hot nodules create excess TSH without signals from the pituitary gland, but they are rarely cancerous.
Cold nodules, on the other hand, do not produce hormones, but they are more likely to be cancerous. However, since ultrasound has been so successful in evaluating the thyroid nodules, a thyroid scan is rarely necessary in the management of thyroid nodules anymore.
Thyroid nodules with a hyperthyroid picture on TSH are rarely cancerous and most of the time, do not need a biopsy.
If you have a suspicious lump near your throat, or believe you have many of the risk factors associated with papillary thyroid cancer, talk to your doctor. He or she will examine your thyroid and will order a thyroid ultrasound to see if you have any nodules requiring a fine needle aspiration biopsy. Remember, the sooner you recognize the symptoms and seek medical care, the more likely you are to respond well to treatment.