Approximately 60 percent of adults have a thyroid nodule, but only 5 percent are cancerous. Improved access to care and more advanced imaging techniques means more of these nodules are found, but is overdiagnosis leading to overtreatment? Is surgery always the right answer or are non-surgical options reasonable to consider?
Thyroid nodules are common findings but nearly all are benign.
Tests such as ultrasound and fine needle aspiration biopsy aid in diagnosis.
Nearly all benign nodules can be monitored without treatment.
Non-surgical options are available for benign nodules causing discomfort or difficulty swallowing.
Developing a treatment plan for thyroid nodules is complex and should be individualized to your situation.
The detection of thyroid nodules — small bumps on the thyroid gland in the throat — has been increasing over the past three decades. Approximately 68% of the general population has nodules, which can be found by ultrasound examination, according to the American Academy of Family Physicians (AAFP).
Most of these nodules are found during a routine exam and are what are called “incidental findings,” which may not have been discovered otherwise. An example of an incidental finding is when a patient is referred for an ultrasound of the neck due to nerve tingling in the arm or fingers, and the ultrasound shows nodules on the thyroid.
Although the rate of thyroid nodule and thyroid cancer detection has been increasing, mortality rates have generally not increased commensurately. A study published last year in Lancet reviews the evolving management of thyroid nodules, from historical approaches that may have been “unnecessary or excessive,” according to the authors, to a much more individualized stance today.
These more individualized treatment courses can include nonsurgical options such as monitoring small, isolated nodules. Even when surgery is the favored treatment, near-total thyroidectomy may not be necessary. Modern treatment recommendations for thyroid nodular disease incorporate research data coupled with a patient’s unique risk factors and test results.
How is thyroid cancer diagnosed?
Your doctor will want to run a series of tests to determine the best treatment path for you. The first set of tests will provide a visual image of the nodule through ultrasound imaging. The sonographer will also be able to take measurements of the nodule to estimate its size, which is very important in determining the best treatment course.
Thyroid ultrasound is not recommended as a routine screening test by the U.S. Preventive Services Task Force unless there is a specific risk, such as a family history of thyroid cancer or a previous exposure to radioactive fallout or radiation treatment.
For patients with a thyroid nodule, the first step in evaluating risk is to determine the thyroid-stimulating hormone (TSH) level. A normal or high TSH suggests the nodule is non-functioning. These nodules are rarely cancerous but further diagnostic work-up is necessary to determine the treatment plan.
A low or suppressed TSH, on the other hand, suggests primary hyperthyroidism.
Nodules greater than 1 cm in size, and those which are firm, fixed, or rapidly growing should be promptly evaluated. Nodules less than 1 cm in size will likely be monitored with repeat ultrasound exams.
Fine-needle aspiration biopsy
Nodules greater than 1 cm in size and those accompanied by a normal or high TSH may require fine-needle aspiration biopsy (FNAB) depending on their size and findings on ultrasound.
The FNAB involves taking a sample of cells using a needle inserted into the thyroid. The cells are examined and graded for risk using the Bethesda System for Reporting Thyroid Cytopathology.
The sonographer looks for “suspicious ultrasound features” such as irregular margins, microcalcifications, nodules that are taller than they are wide, nodules growing out of the thyroid gland, or lymph node involvement.
Nodules with suspicious ultrasound features proceed to FNAB if at least 1 cm in size; smaller suspicious nodules will be recommended for a repeat ultrasound in six to nine months.
Nodules without suspicious ultrasound features are further classified according to their specific characteristics. Some will be recommended for FNAB while others will be recommended for repeat ultrasound in 12 to 24 months.
If FNAB sample cytology is inconclusive, as approximately 25 percent are, the next step is typically surgery. However, approximately 80 percent of these indeterminate samples were found to be benign. A newer option — molecular testing — sequences the genes to look for evidence of cancer-causing mutations and reduces the need for surgery.
Over the past decade, gene sequencing has become more useful for detecting mutations that give rise to thyroid cancers. Many indeterminate samples are now automatically run through molecular testing. As more research becomes available on the test's capacity to correctly classify nodules, it will be possible to estimate sensitivity and specificity.
High sensitivity means more cancers are correctly classified while high specificity reduces false positives leading to surgery. Molecular testing is still in its infancy, and long-term follow-up of benign nodules is lacking. In the meantime, the AAFP recommends ongoing ultrasound surveillance for indeterminate thyroid nodules.
One barrier to use of molecular testing is the high cost of these tests, but avoiding unnecessary surgery also has economic and quality of life benefits.
Who is most at risk for thyroid cancer?
Most thyroid cancers are found in people older than 40 years. Other risk factors include hereditary syndromes such as PTEN hamartoma tumor syndrome, Carney complex, and Werner syndrome.
The location of the nodule in the thyroid may also suggest differences in risk. For instance, nodules in the isthmus or intraglandular nodules are more likely to be malignant. Nodules found in the lower third of the thyroid gland are lower risk than those in the middle or upper third.
What happens if cancer is found?
For those whose cytology returns a malignant finding (Bethesda classes V and VI), immediate surgery is recommended. If the cytology is “suspicious” for cancer or the nodule is smaller (<1 cm), active ultrasound monitoring may be an alternative to consider and discuss with your doctor.
Nodules less than 1 cm in size and in a lower-risk location within the thyroid can be considered for active ultrasound monitoring every six months. If the nodule remains stable (without disease progression) over the course of two years, then the frequency of screening can be reduced.
"Disease progression" is considered growth of 3 mm or more in diameter, growth out of the surface of the thyroid, or spread to the lymph nodes.
People who are appropriate for active ultrasound monitoring have cancers that tend to remain stable and are less likely to spread. This option is particularly useful for older patients in whom disease progression is less likely.
What non-surgical options are available?
For benign (non-cancerous) nodules, treatment is rarely needed. For hyperfunctioning thyroids, the most common reason for treatment is growth compressing the trachea, causing problems with swallowing.
Non-surgical options for managing a hyperactive thyroid include ablation by injecting ethanol. An ultrasound is used to guide the needle into the nodule to deliver the ethanol.
Other non-surgical treatment options include laser, high-intensity focused ultrasound, radiofrequency, or microwave energy. Each procedure has associated risks and benefits, including pain, fever, voice changes, and hypothyroidism. The treatment with the fewest side effects is ethanol injection. Right now, the general approach is ethanol injection followed by thermal ablation if symptoms continue.
When is surgery appropriate?
If the nodules could not be classified with FNAB cytology, then surgery may be appropriate depending on the size, location, and involvement of lymph nodes. Most nodules smaller than 1 cm can be followed closely with active ultrasound monitoring.
If surgery is recommended, the most minimally invasive option is used to spare the thyroid as much as possible. The recommended surgical treatment will consider the nodule size, number of nodules, and other risk factors.
Lobectomy — removing part of the thyroid instead of the entire gland — offers many benefits for the patient. Nerve injury is avoided and permanent thyroid hormone replacement may be minimized, but this depends on the initial TSH level and any autoimmunity.
Individualized treatment plans
The appropriate treatment plan should consider age in addition to the clinical and ultrasound characteristics of the nodule. Patients older than 60 tend to have slower-growing nodules while those younger than 40 may have more tumor growth and an increased likelihood of spreading to the lymph nodes.
As with many medical decisions, some uncertainty is inevitable. It may be difficult for some patients, and some clinicians, to avoid extensive testing, which may lead to unnecessary surgery.
According to the AAFP, “It is reasonable to consult an endocrinologist when formulating an individualized management plan.” If you have a thyroid nodule, talk to your doctor about whether a referral to an endocrinologist would be helpful. This may be particularly helpful if you have thyroid cancer and are going through menopause at the same time.
A good doctor welcomes a second opinion, and you will likely derive some reassurance knowing you got as much information as possible before pursuing a procedure or deciding on a wait-and-see approach through active ultrasound surveillance.
- American Academy of Family Physicians. Thyroid Nodules: Advances in Evaluation and Management.
- Lancet Diabetes and Endocrinology. Management of thyroid nodules.
- Journal of Clinical Endocrinology and Metabolism. Contemporary Thyroid Nodule Evaluation and Management.