What is a Thyroid Nodule?
Thyroid nodules are defined as abnormal growths within the thyroid gland. These commonly occur as lumps within a normal thyroid gland which can often be seen on imaging such as ultrasound or CT scan. Sometimes, patients may notice a lump in their neck while looking in the mirror or putting on a collared shirt or necklace – but most thyroid nodules are not noticeable to the patient. Sometimes, if the nodule is large enough, patients can feel a lump in the throat or have difficulty with swallowing, but this is relatively rare.
The best way to determine if you have a thyroid nodule is to make sure your primary care doctor checks your neck. A primary care physician may discover a thyroid nodule during a physical examination and may refer you for an ultrasound to evaluate the nodule, or directly to an endocrinologist.
A thyroid nodule can represent many things. It may represent a growth of normal thyroid tissue, also known as hyperplasia. Other times, it can be a cyst, or fluid filled cavity. Finally, in less than 10% of cases, it can represent a thyroid cancer.
Thyroid cysts are usually benign but can contain malignant (cancerous) solid particles. Cysts can often recur even after drainage, so they are only intervened upon if there is concern for cancer or if they are bothersome to the patient.
Thyroid hyperplasia, or overgrowth or normal tissue, can be caused by many conditions including genetic conditions, iodine deficiency, or endocrine disorders. These may manifest with symptoms of hyperthyroidism including sweating, shakiness, diarrhea, heart palpitations, weight loss, and excitability. Most often, however, there are very few symptoms.
If you are referred to an endocrinologist for a thyroid nodule, he or she may order lab work to determine if the rest of your thyroid gland is healthy or if the gland is causing conditions such as hyperthyroidism or hypothyroidism. Sometimes, a physical examination and lab results alone aren’t enough to determine if a thyroid nodule is cancerous. In these cases, the endocrinologist may order an ultrasound to take a closer look at the nodule and surrounding thyroid gland. Ultrasound can help determine the characteristics of a nodule, such as whether it is mostly solid or fluid filled. It can also help determine if there are other nodules in the thyroid gland that have not yet been detected. Finally, it can evaluate the overall size of the thyroid gland. This information can help your endocrinologist or primary doctor determine whether or not a biopsy of your thyroid gland is required.
Patients who undergo an ultrasound evaluation feel no pain during or after the evaluation.
If the physician determines that further evaluation is required, he or she may order a thyroid fine needle aspiration (FNA) of the nodule. While the name of this procedure might sound scary, the needle used is so thin that many times no anesthetic (pain killer) is needed. An FNA allows your doctor to remove cells from within the thyroid nodule and send them to a pathologist. The cells are then examined under a microscope to determine if they are cancerous or not.
Your doctor might ask you to stop taking blood thinners prior to the procedure but usually the procedure requires nothing else from you. You don’t even have to fast beforehand! Most patients return to work or home right after the procedure and usually without a bandaid.
Your biopsy report will usually show one of the results below:
- That the nodule is noncancerous (benign).
This is the result up to 80% of the time. Benign nodules are only removed if they interfere with the patient’s ability to breathe or swallow or causes symptoms such as choking. Your doctor may want to follow these nodules with additional ultrasound exams every six months to one year, and may need to conduct another biopsy if the nodule grows.
- That the nodule is cancerous (malignant) or is suspected of being cancerous
About 5% of the time, the thyroid nodule is identified as or is suspected of being cancerous. Papillary cancer is the most common type of thyroid cancer, with follicular carcinoma being the next most common type. Rarely cancers such as Medullary Thyroid Carcinoma and Anaplastic Thyroid Carcinoma can be diagnosed by needle bopsy. When the nodules is diagnosed as cancer by the endocrinologist it almost always has to be removed by surgery. Learn more about Thyroid Nodule Surgery.
- That the nodule is indeterminate.
In up to 20% of cases, the nodule may be ruled as indeterminate. This means that even though numerous cells were removed and evaluated as part of the biopsy, a pathologist could not determine if the cells were cancerous or non-cancerous.
If the pathologist describes the nodule as a Follicular Lesion of Undetermined Significance (FLUS) or Atypia of Undetermined Significance (AUS), there is a 20-30% chance that the nodule is cancerous. In these instances, only surgical examination of the thyroid can determine if the nodule is cancerous or not. Since the likelihood that the nodule is not cancerous is 70-80%, only the nodule-containing half of the thyroid gland is removed for examination. If the nodule is determined to be cancerous, the remainder of the thyroid gland is removed. However if it is not cancerous, the thyroid gland is not removed and no additional surgery is performed.