Detecting Thyroid Cancer
Most people have no symptoms of thyroid cancer. Those who do have symptoms, however, may notice a lump in their neck that appears to be getting larger. You may also notice pain in the front of your neck or that your voice is suddenly hoarse for no apparent reason. Some people experience difficulty swallowing or have trouble breathing easily. In others, thyroid cancer may cause a constant cough that doesn't go away. All of these symptoms warrant medical attention and immediate biopsy.
Finding a lump in your throat might be frightening. Keep in mind, however, that most lumps or nodules are benign and non-cancerous. The only way to know for sure is to see your doctor as soon as you can. Your doctor will do a physical exam and ask you about your medical history and family history. Your doctor will also need to perform some tests. The most important one is the FNA biopsy.
Fine Needle Aspiration (FNA) Biopsy
The simplest and most direct way for detecting thyroid cancer is with an FNA of the lump or nodule. The FNA is the key to diagnosing thyroid cancer. It is an office procedure that involves using a thin needle to obtain cells from the nodule, which are then examined by a pathologist for cancer.
To perform this test, your doctor will have you lie down, with your neck extended backward and a pillow under your shoulder for comfort and support. Local anesthesia is sometimes applied to the area over the nodule, though some patients may not want any anesthesia at all. A thin needle is then inserted into the nodule for several seconds and cells are withdrawn.
This procedure can tell you whether the lump is cancerous or benign. If the nodule is cancer, the FNA can reveal what kind of cancer it is.
If you don't like needles, ask your doctor for a sedative before a biopsy. Some patients may be given a drug such as Valium to ease their worried minds. You might also want to practice deep breathing or meditation to help you stay calm.
The procedure is often repeated several times so that cells can be collected from different parts of the nodule. The cells are then sent to a lab and examined by a pathologist. Most times, the FNA is highly accurate in diagnosing papillary and medullary thyroid cancers. But in people who have follicular thyroid cancer, an FNA is often not accurate or is inconclusive. If the biopsy shows follicular cells, the patient may go for surgery, or the nodule may be watched for several months to see if it grows. A nodule that is rapidly growing is likely to need surgery.
Sometimes there may not be enough cells in the aspirate — the substance collected by this needle — and the biopsy is called nondiagnostic. In that case, the FNA needs to be repeated.
Physicians often use ultrasound to help diagnose thyroid cancer. An ultrasound is helpful in determining the size of the nodule and how many nodules there are. In addition, ultrasounds are helpful in determining whether a nodule is fluid filled or solid. Both types can be thyroid cancer.
Many doctors use ultrasound at the time of the FNA to assist in the placement of the needle. An ultrasound is also used after a portion of the thyroid has been removed, when scarring from the surgery has made it more difficult for your doctor to examine your remaining thyroid gland.
An ultrasound is done using a transducer wand. Jelly is applied to the region being examined, in this case the neck. The transducer is then moved along the neck, creating sound waves that form an image of your thyroid on a computer screen. The procedure is painless and not invasive.
Ultrasounds can be effective at finding cancer after the thyroid gland is removed if the cancer comes back in the neck or elsewhere in the body. But an ultrasound image is by no means conclusive. It only provides evidence that there may be a recurrence of cancer and that a biopsy is needed. Sometimes, tiny nodules are found by ultrasound but do not need to be biopsied.
Nuclear imaging is undoubtedly an invaluable tool in diagnosing and treating thyroid diseases. But in people with thyroid cancer, a thyroid scan is mostly used to determine whether the cancer has spread.
Most types of thyroid scans involve two steps: the scan itself and an RAIU test. For the procedure, you will be given a pill or an injection that contains RAI. Several hours later, a camera is placed in front of your neck to take a picture of where the iodine is concentrated in your neck. You may also get a test called a thyroid uptake that measures the amount of radiation taken up by the thyroid.
There are two types of iodine used for thyroid scans. Iodine-123 and 131. Generally, I-123 has a shorter half-life and leaves the body sooner. But I-131 may be more effective because it stays in the tumor longer. Scans may also be done with an element called technetium.
Areas of the thyroid that do not take up iodine are considered cold nodules because they do not show radioactivity. Nodules that have absorbed iodine will turn up as hot nodules. Hot nodules may occur in hyperthyroidism. The problem with the thyroid scan as a diagnostic tool in cancer is that virtually all nodules, both malignant and benign, appear cold, making it impossible to distinguish the benign from the malignant.
But thyroid scans are of use in patients who have had their thyroid glands removed because of papillary or follicular thyroid cancer. Any remaining cancer cells will take up the radioactive iodine and appear on the scan. Thyroid scans are not used for medullary forms of thyroid cancer since the cancer cells in that disease will not absorb iodine.
Other Diagnostic Tools
FNA and ultrasound are the primary ways for diagnosing thyroid cancer. But your doctor may use other tools as well to help determine whether the cancer has spread. For example, your doctor may use computerized axial tomography (CAT) scans. CAT, or CT, scans are advanced X-rays that shoot several beams from different vantage points, which are then viewed on a computer screen, not film. The CT scan gives you a glimpse of the surrounding muscles, including the trachea, the esophagus, and the lymph glands.
Your doctor may also use magnetic resonance imaging (MRI), which uses a magnet to create vibrations in a targeted area, then produces a detailed image on a computer. Like the CT scan, an MRI can tell you the size of a thyroid nodule and whether it has spread to other parts of the body.
If you have a difficult or aggressive tumor, your physician may recommend a positron emissions tomography (PET) scan. PET scans of the thyroid require the use of radioactive glucose.
Besides cancer, PET scans are used to help diagnose neurological problems, including Alzheimer's disease. In people with Alzheimer's, a PET scan will show less activity in certain parts of the brain than that which occurs in a healthy person.
Because thyroid cancer cells have a faster metabolism than normal cells, they will take up the glucose at a more rapid rate. The radioactivity is then seen with the use of special scanning equipment and used to form an image of the tumors in the body. PET scans are just starting to be used by doctors, but may be useful for detecting recurrent cancer and to pinpoint the spread of cancer.