What is a thyroid nodule?
The thyroid gland is located in the lower front of the neck, above the collarbones, and below the voice box (larynx). A thyroid nodule is a lump in or on the thyroid gland. Thyroid nodules
are common, but are usually not diagnosed. They are detected in about six percent of women and one to two percent of men. They are 10 times as common in older individuals than in younger ones. Sometimes several nodules will develop in the same person. Any time a lump is discovered in thyroid tissue, the possibility of malignancy (cancer) must be considered. Fortunately, the vast majority of thyroid nodules are benign (not cancerous).
Most patients with thyroid nodules have no symptoms whatsoever. Many are found by chance to have a lump in the thyroid gland on a routine physical exam or an imaging study of the neck done for unrelated reasons (CT or MRI scan of spine or chest, carotid ultrasound, etc.). In addition, a substantial number are first noticed by patients or those they know who see a lump in the front portion of the neck, which may or may not cause symptoms, such as a vague pressure sensation or discomfort when swallowing. Obviously, finding a lump in the neck should be brought to the attention of your physician, even in the absence of symptoms.
Nodules can be caused by a simple overgrowth of “normal” thyroid tissue, fluid-filled cysts, inflammation (thyroiditis), or a tumor (either benign or cancerous). Most nodules were surgically removed until the 1980s. In retrospect, this approach led to many unnecessary operations, since fewer than 10 percent of the removed nodules proved to be cancerous. Most removed nodules could have simply been observed.
What is a thyroid needle biopsy?
A thyroid fine needle biopsy that employs a very thin needle, usually smaller than one used to draw blood, is a simple procedure that can be performed in the physician’s office. Many physicians numb the skin over the nodule prior to the biopsy, but it is not necessary to be put to sleep, and patients can usually return to work or home afterward with no ill effects. This test provides specific information about a particular patient’s nodule; information that no other test can offer short of surgery. Although the test is not perfect, a thyroid needle biopsy will provide
sufficient information on which to base a treatment decision more than 75 percent of the time, eliminating the need for additional diagnostic studies.
Use of fine needle biopsy has drastically reduced the number of patients who have undergone unnecessary operations for benign nodules. However, about 10-20 percent of biopsy specimens are interpreted as inconclusive or indeterminate; that is, the pathologist cannot be certain
whether the nodule is cancerous or benign. This is a gray zone category that calls for a repeat biopsy in most instances for additional studies. Some biopsies are insufficient or nondiagnostic. These are nodules that contain very few thyroid cells to examine. In such cases, a physician who is experienced with thyroid disease can use other criteria to make a decision about whether or not to operate. The fine needle biopsy can be repeated in those patients whose initial attempt failed to yield enough material to make a diagnosis. Many physicians use thyroid ultrasonography to guide the needle’s placement. The use of molecular testing (not widely use by many operators except for high volume thyroid practices) has become a tool to better determine the nodules that can be conservatively followed versus those for which surgery is required.
What is a thyroid scan?
A thyroid scan is a picture of the thyroid gland taken after a small dose of a radioactive isotope normally concentrated by thyroid cells has been injected or swallowed. The scan tells whether the nodule is hyperfunctioning (a “hot” nodule), or taking up more radioactivity than normal thyroid tissue does, taking up the same amount as normal tissue (a “warm” nodule), or taking up less (a “cold” nodule). Because cancer is rarely found in hot nodules, a scan showing a hot nodule eliminates the need for fine needle biopsy in most instances. If a hot nodule causes hyperthyroidism, it can be treated with radioiodine or surgery.
Neither a thyroid scan nor radioiodine treatment should ever be given to a pregnant woman!
Small amounts of radioactive iodine will also be excreted in breast milk. Since radioiodine could permanently damage the infant’s thyroid, breast-feeding is not allowed. If radioiodine is inadvertently administered to a woman who is subsequently discovered to be pregnant, the advisability of terminating the pregnancy should be discussed with the patient’s obstetrician and endocrinologist. Therefore, prior to administering diagnostic or therapeutic radioiodine treatment, pregnancy testing is mandatory whenever pregnancy is possible.
Fortunately, the vast majority (90 – 95 percent) of thyroid nodules are benign. Unfortunately, thyroid scans show that most thyroid nodules, both benign and malignant, are cold or nonfunctioning. Therefore, although almost all thyroid cancers are nonfunctional on scan, the majority of nonfunctional nodules are benign. For this reason, thyroid scans are of relatively little value in most patients unless TSH levels are toward the lower end of the normal range or below the normal range.
What is thyroid ultrasonography?
Thyroid ultrasonography is a procedure for obtaining pictures of the thyroid gland by using high-frequency sound waves that pass through the skin and are reflected back to the machine to create detailed images of the thyroid. It can visualize nodules as small as two to three millimeters. Ultrasound distinguishes thyroid cysts (fluid-filled nodules) from solid nodules. Many nodules have both solid and cystic components, and very few purely cystic nodules occur. Recent advances in ultrasonography help physicians identify nodules that are more likely to be cancerous.
Thyroid ultrasonography is also utilized for guidance of a fine needle for aspirating thyroid nodules. Ultrasound guidance enables physicians to biopsy the nodule to obtain an adequate amount of material for interpretation. Such guidance allows the biopsy sample to be obtained from the solid portion of those nodules that are both solid and cystic and it avoids getting a specimen from the surrounding normal thyroid tissue if the nodule is small.
Even when a thyroid biopsy sample is reported as benign, the size of the nodule should be monitored. A thyroid ultrasound examination provides an objective and precise method for detection of a change in the size of the nodule. A nodule with a benign biopsy that is stable or decreasing in size is unlikely to be malignant or require surgical treatment.
How are thyroid nodules treated?
Your endocrinologist will use the tests mentioned above to arrive at a recommendation for optimal management of your nodule. Most patients who appear to have benign nodules require no specific treatment, and can simply be followed. Some physicians prescribe levothyroxine (thyroid suppression) with hopes of preventing nodule growth or reducing the size of cold nodules, while radioiodine may be used to treat hot nodules. Thyroid suppression in areas that are considered iodine sufficient or for larger nodules is not considered to significantly affect the size of the nodules and may lead to adverse cardiac and bone outcomes therefore selective use is recommended.
If cancer is suspected, surgical treatment will be recommended. The primary goal of therapy is to remove all thyroid nodules that are cancerous; and, if malignancy is confirmed, remove the rest of the thyroid gland along with any abnormal lymph nodes. If surgery is not recommended, it is important to have regular follow-up of the nodule by a physician experienced in such an evaluation.