Thyroid nodules, or growths within the thyroid, are usually seen in patients who have a normally working thyroid gland. Thyroid nodules are lumps that are solid or filled with fluid that form within your thyroid.
The reasons for developing a nodule are unclear. It is thought that hormones and diet may play a role, but pinpointing the dietary factors has proven difficult. Genetics can also play a role, so if thyroid issues run in the family (especially cancer), be sure to tell your doctor. Cancer can be found in these growths, which is the reason they usually need to be further investigated. Thyroid nodules are present in greater than 50% of the population, and overall, roughly 10-15% will be cancerous on final biopsy.
Nodules can cause symptoms depending on their size. Patients may experience a sensation of needing to clear their throat, or have difficulty swallowing. Sore throat and voice changes can also occur. There are several other reasons to have these symptoms, and only your doctor can tell for sure if these symptoms are caused by the thyroid.
Some patients may have only one nodule, or there can be multiple nodules. In general, the more nodules that are present, the more likely it is that the nodules are not cancerous. If the thyroid is enlarged and multiple nodules are present, this is termed a thyroid goiter. Once nodules are present on both sides, patients are more likely to develop symptoms of ‘compression’ with difficulty swallowing and pressure on their trachea (windpipe).
Diagnosis of Thyroid Nodules
Once a nodule is found, either noticed by the patient themselves or by a doctor, an ultrasound is usually ordered. This is the most sensitive test for the thyroid and can determine the size and number of nodules. Ultrasound can also determine if there are any suspicious characteristics of the nodule which will let us know if there is a possibility of cancer. If a nodule is larger than 1 centimeter, a biopsy is recommended to determine the risk of cancer within the nodule. This is in the form of a fine needle biopsy. Ultrasound will guide the small biopsy needle into the most suspicious area of the growth. This is a procedure that is done in an office or outpatient setting. Most commonly, an endocrinologist, radiologist, or surgeon will perform this procedure. This takes around 15-20 minutes for the actual biopsy, and most patients have only mild discomfort.
The Results of the Biopsy Generally Fall into One of Four Categories
- Benign: The majority of nodules are benign, meaning no cancer. These nodules can be observed with routine ultrasound, but if they enlarged, a repeat biopsy or surgery may be indicated.
- Malignant: Cancer of the thyroid can usually be determined or strongly suspected based on this biopsy. If cancer is determined, then surgery is needed to remove the thyroid. Thyroid cancer is typically very slow growing, but surgery is usually undertaken fairly swiftly.
- Indeterminate: This is the result when there are too many cells placed closely together, but we can’t tell if there is cancer or not unless we can inspect the capsule of the nodule. This can only be done with the portion of the thyroid containing the nodule removed (with surgery). The concern in this case is that the nodule represents a cancer called Follicular.
- Insufficient: This means that there were not enough cells collected in the biopsy for the pathologist to make a determination of what the lesion is. In this case, typically the biopsy is repeated, or further surveillance can be suggested.
Other tests can be done to evaluate the thyroid. A thyroid scan (aka nuclear medicine or iodine scan) can help determine the source of overactive thyroid. A thyroid scan uses a radioactive tracer and a special camera to measure how much tracer the thyroid gland absorbs from the blood. The tracer can be swallowed or injected. The scan can show the size, shape, and location of the thyroid gland.
Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI) are also available. These are used mainly in cases of cancer recurrence, and not routinely used. However, many patients are initially found to have a thyroid nodule when a CT or MRI is done for another reason.
Once a nodule has been diagnosed as benign, routine ultrasound is used at 6 or 12 month intervals to see if the nodule is growing. If the thyroid is under-active, nodules are more likely to enlarge. If a nodule enlarges, even though a biopsy was benign, it should be further treated with a second biopsy or surgery to remove it.
When Would Surgery Be Considered?
- Enlarging thyroid nodules
- Nodules suspicious or positive for cancer
- Symptomatic nodules or benign goiter causing symptoms