Once a thyroid nodule has been detected (or suspected), there are a few things that the physician will want to know before any recommendations can be made regarding treatment. Remember, the vast majority of thyroid nodules are benign and nothing to worry about, so the focus is on determining which ones have any reasonable chance of being cancerous. It is those few worrisome nodules that will need to be operated upon with that portion of the thyroid removed.
One of the first tests that is routinely performed is the fine needle aspiration biopsy. The FNA will usually (but not always) tell if a nodule is benign or malignant. This is often the only test needed.
Another common test is the ultrasound. This simple test uses sound waves to image the thyroid. The sound waves are emitted from a small hand-held transducer that is passed over the thyroid. A lubricant jelly is placed on the skin so that the sound waves transmit more easily through the skin and into the thyroid and surrounding structures. This test is quick, accurate, cheap, painless, and completely safe. It usually takes only about 10 minutes and the results can be known almost immediately. Not all nodules need this test, but it is almost routine.
Do I Need A Test?
The above image is an ultrasound of a typical thyroid nodule, except that this nodule is a bit bigger than usual. The two scans are identical, the one on the right is outlined to help you understand what you are looking at. The probe is placed on the skin, which is at the very top of the picture, and sound waves are directed deep into the neck and thyroid (toward the bottom of the picture).
As sound waves hit structures they bounce back like an echo. The probe detects these reflections to make pictures. This nodule (shown in red) comprises about 80% of the thyroid tissue (shown in yellow) in this particular area of the thyroid. If you looked at other parts of the thyroid, however, you would not see the nodulem; you would only see normal thyroid tissue.
Certain characteristics of thyroid nodules seen on an ultrasound are more worrisome than others. Keep in mind, however, that an ultrasound alone cannot make the diagnosis of cancer. This test will usually help determine that the nodule has a low chance of being cancerous (has characteristics of a benign nodule), or that it has some characteristics of a cancerous nodule, and therefore a biopsy is indicated.
Ultrasound Characteristics That Suggest a Benign Nodule
This patient had no other nodules in her thyroid, so this was diagnosed as a "dominant complex nodule of the right thyroid lobe."
Since this nodule does have a few worrisome characteristics, a fine needle aspirate biopsy (FNA) was performed. In this test, a very small needle is passed into the nodule and some cells are aspirated out and then placed on a glass slide for a pathologist to stain and determine if they are malignant.
This test is very simple; it takes less than 30 seconds, is virtually pain free, and can be very accurate. If it is read as cancer, this test is almost always right.
Sometimes, however, there are not enough cells removed or some, but not all, cells look abnormal. In this case, the pathologist will not be able to tell cancer from a benign nodule. This situation usually dictates that the test be repeated or that the patient undergo surgical removal of this part of the thyroid. Remember, the vast majority of nodules are benign, and even if it is cancer, most thyroid cancers are extremely curable.
This patient had two indeterminate FNAs performed. Both needle biopsies had good tissue specimens, but the pathologist could not distinguish benign from cancer. She subsequently underwent a simple right thyroid lobectomy, and the final diagnosis was a benign follicular adenoma. She did fine after the operation and has enough normal thyroid still in her neck, so she does not have to take thyroid hormone pills.