Thyroid Disorders Thyroid Nodules

Thyroid nodules, or lumps, are quite common, occurring in more than 50% of the world's population. Moreover, the likelihood of developing a thyroid nodule increases with age and in part represents the aging process of the thyroid gland. Although most nodules are harmless and do not require any treatment at all, approximately 5% of all nodules are cancerous. Thyroid nodules occur more frequently in women than in men, however the incidence of cancerous nodules is greatest in men. Despite the low incidence of cancer, all nodules should be evaluated by a physician to determine their status.

Although the cause of most thyroid nodules is unknown, some risk factors for developing nodules include a lack of iodine in the diet, which can cause thyroid enlargement, family history of benign thyroid nodules, and pre-existing thyroid disease (e.g. Hashimoto's thyroiditis).

Detection

Most thyroid nodules do not cause any symptoms like neck pain or fever, therefore most remain unnoticed until a physician finds them during a routine neck exam. Make sure to ask your physician (your internist, family practice doctor or gynecologist) to check your neck during routine visits. Although most nodules are small, some can even be seen just by looking at the front of your throat. Since the thyroid gland moves with every swallow that you take, a thyroid nodule will also move. Therefore most doctors will ask you to swallow while they are examining your thyroid gland.

Diagnosis

In order to diagnose the nature of a thyroid nodule, the physician evaluates the patient's medical history and performs a physical examination. The history is important since some types of thyroid cancer are inherited and may be associated with other endocrine problems. In addition, radiation exposure of the head and neck is associated with thyroid cancer, particularly when administered in low doses at a young age (see details on risk factors for thyroid cancer). Certain characteristics which may indicate that a nodule is cancerous include:

• a single nodule in a thyroid gland that is otherwise apparently normal
• a hard nodule
• enlarged lymph nodes in the neck region
• no decrease in nodule size after thyroid hormone medication
• a nodule that is "cold" on radioactive iodine scan
• a nodule that is very hard or fixed to surrounding structures

Screening Tests

Blood Tests

In addition to the history and the physical examination, blood tests may also help to diagnose a nodule. These tests check Thyroid Stimulating Hormone level (TSH), thyroid hormone level, and thyroid antibodies: antiperioxidases (anti-TPO) or antithyroglobulin (anti-Tg). All patients with a thyroid nodule should undergo thyroid function blood tests to determine if they have an underactive or overactive thyroid problem. It is important to note, however, that most patients with thyroid cancer do not have either hypo- or hyperthyroidism; rather they have normal thyroid function despite their cancer.

Biopsy

A biopsy is the removal of a small amount of fluid or tissue from the thyroid by needle insertion for further microscopic examination. There are two types of biopsies, a fine needle aspiration and a coarse (large) needle biopsy. Both types are safe and can be done in the physician's office. The results of the biopsy may lead the physician to recommend surgery or to prescribe thyroid hormone tablets. Usually thyroid biopsies provide the most definitive conclusions about the nature of thyroid nodules, often eliminating the need for radioiodine scanning.

• Fine-Needle Aspiration (FNA)
  An FNA is the removal of a few clusters of individual thyroid cells by means of a small needle (smaller than the type used to draw blood). If you have more than one thyroid nodule, this technique can be used on each of them whenever practical, with special attention to nodules that have recently grown in size. The cells are then examined microscopically by a cytopathologist and the results of this test are usually available within a few days. (See recommendations based on biopsy diagnoses.)
  
  No test is a perfect test, and fine needle aspiration biopsy can very rarely be wrong. About three percent of the time, the biopsy result will be benign, but the nodule will actually be a cancer. This mistake is called a false-negative result and usually results from the fact that the needle was not inserted directly into the cancer. Either the needle missed the nodule or the needle sampled areas of the nodule that were benign, not cancerous. If a nodule is very small, it is possible to miss it completely with the needle. On the other hand, the larger a nodule is, the higher the probability of this sampling error, since only part of the nodule may be cancerous. The more experienced the physician is at performing these biopsies, the smaller the risk of missing the nodule or not sampling all areas. However, these risks can never be eliminated entirely. Therefore it is very important to have follow-up even if the initial biopsy report is benign.
• Coarse-Needle Biopsy (CNB)
  A CNB is the removal of a core of thyroid tissue from the nodule using a larger needle. In addition to providing information about individual cells, this method provides an architectural pattern of connection between cells. Unlike the FNA, which can be performed on all types of nodules, the nodule must be at least 3/4 of an inch in size in order to successfully perform a CNB. Extensive studies have shown that those who have had a CNB are less likely to be recommended for surgery than those who have not had this type of biopsy.
  
  In general, a CNB allows for more accurate results, but it is more difficult to do and there are few physicians with experience in this procedure. If a nodule is very low in the neck or if a patient is obese, it may be difficult to perform this biopsy from a technical standpoint. In addition, because the needle is large, there is a very small risk (less than 1%) of bleeding or injury to the windpipe or nerves controlling the vocal cords.

Thyroid Ultrasound

The ultrasound uses sound waves to create an accurate picture of the shape of the thyroid and the size of the nodules within it. In addition, it can distinguish between solid, fluid (cystic), and complex nodules. Ultrasound is sometimes used to evaluate changes in the size of nodules as patients are followed over a period of time. In addition, there are certain characteristic ultrasound findings (such as increased vascularity, punctuate calcifications) that suggest a cancer. However, since it can not always distinguish between cancerous and benign nodules, it is used in conjunction with a thyroid biopsy for definitive diagnosis.

If a nodule is too small to be felt (usually less than 1.5 cm, about 3/4 of an inch) and if you do not have any risk factors for thyroid cancer, a follow-up physical examination in about 6 months is generally recommended. If the nodule still can not be felt at that time, the physical examination is repeated on a yearly basis to continue to monitor the growth of the nodule. Some physicians advocate performing a biopsy on all of these tiny nodules. The issue of what should be done with these small nodules remains a controversial area for thyroid physicians, although it is not known which option is best.

If the nodule is greater than 1.5 cm (3/4 of an inch), but still can not be felt on physical examination, an ultrasound guided fine needle aspiration biopsy is generally recommended. This is the same as performing a fine needle aspiration biopsy (see above), however, by using the ultrasound machine, a simultaneous picture of both the nodule and the needle are obtained. In this way, the practitioner can guide the needle into the nodule under direct ultrasound vision to be certain that the cells that are sampled are from the nodule itself and not from the normal surrounding thyroid tissue. The results of this biopsy will help to determine if the nodule is benign or malignant. (See recommendations based on biopsy diagnoses.)

Radioactive Iodine Scan

A radioactive iodine scan is obtained to determine information about thyroid hormone function. This test involves the ingestion of a small amount of radioiodine, a form of iodine that emits energy so that it can be detected once it is inside the body. A picture of the thyroid region is obtained by tracing the ingested radioiodine within a few hours or the next day depending on the information desired. Nodules can be referred to as either "hot" or "cold." A nodule is hot if it has a high concentration of radioactive iodine. Conversely, a cold nodule does not concentrate radioactive iodine. "Hot" nodules are seldom cancer. In contrast, up to 10% of "cold" nodules may be a cancer.

Recommendations Based on Biopsy Diagnosis

A cytopathologist examines each slide produced from an FNA and divides the diagnoses into four categories: 1) benign 2) malignant 3) indeterminate and 4) nondiagnostic.

• Benign
  Most nodules are found to be benign. When this is the case, a follow-up physical examination in six months is generally recommended. If the nodule is the same size or smaller after six months, yearly follow-up is then recommended. However, if the nodule has grown within the first six months, a second biopsy is generally recommended and a course of action is determined depending on the results of this second biopsy.
  
  There are a few situations in which thyroid surgery may be recommended, even if the biopsy result is benign. If a nodule is so large that it presses on the windpipe and/or the esophagus, it will cause difficulty breathing (particularly when you lie down at night) and/or swallowing food. In these situations, thyroid surgery removes the pressure in this area of the neck. In addition, if these symptoms are ignored for many years and the nodule continues to grow, the problem may become so severe that emergency surgery is necessary. For example if your windpipe (trachea) is narrowed as a result of thyroid gland enlargement and you get a common cold or flu, the mucous and phlegm caused by that cold may be just enough to close off the airway entirely.
  
  Other people with benign thyroid disease may choose to undergo thyroid surgery for cosmetic reasons. Although the nodule may not be causing symptoms, the lump in the throat may make you be self-conscious about the way the neck lump looks. Many people wear scarves or turtlenecks to try to hide their lump. Although thyroid surgery leaves a small scar, the scar is often less conspicuous than the lump, particularly since it is usually hidden in a natural fold of the neck.
• Malignant
  If an FNA reveals that a nodule is cancerous, surgery is recommended to remove it. The accuracy of a cancer diagnosis by needle biopsy is close to 100%. It is important to keep in mind that the experience of the pathologist is extremely important in this setting. Therefore, it is often useful to have slides reviewed by another pathologist if the pathologist is not known to be experienced in this area.
• Indeterminate
  Nodules that are diagnosed by FNA as indeterminate or suspicious fall somewhere between benign and cancerous lesions. In this situation, anywhere from 10 to 60% of these nodules are actually cancerous, but there is no perfect way to tell which ones are benign short of performing thyroid surgery to remove the nodule completely. Occasionally, before surgery is recommended, a coarse needle biopsy may be recommended to obtain a more definitive diagnosis.
• Nondiagnostic
  A nondiagnostic fine needle aspiration biopsy results when there are not enough thyroid cells to make a definite diagnosis. A nondiagnostic diagnosis occurs about 10% of the time and can sometimes be due to a physician's inexperience with the biopsy technique. However, sometimes thyroid nodules can be filled with blood, hard material called calcium or fluid and therefore only sparse cells are obtained at biopsy regardless of the experience of the physician.

Because up to 10% of these nondiagnostic thyroid nodules are cancers, a repeat fine needle aspiration biopsy or coarse needle biopsy is usually recommended in order to make a diagnosis. About half the time, the second biopsy will produce a more definitive diagnosis. If a diagnosis still can not be made after the second biopsy either very close follow-up (in three months) to see if the nodule has grown or thyroid surgery is generally recommended in order to make the definite diagnosis.

Treatment with Thyroid Hormone Medication

Occasionally, if a fine needle aspiration biopsy is nondiagnostic, we recommend thyroid hormone medication in order to shrink the nodule. This treatment is still controversial because about one third to one half of all thyroid nodules shrink spontaneously without medication. Research reports are conflicted regarding whether or not thyroid hormone medication will shrink all thyroid nodules, although most practitioners agree that a certain subset of these nodules will shrink. Unfortunately, it is difficult to determine which nodules will respond to the medication and which nodules won't.

Taking thyroid hormone medication is not without risks. If you take doses of thyroid hormone that are too high, you can develop osteoporosis and/or heart disease. Therefore it is important to be carefully monitored on this medication. If you are taking a dose that is right for you, there are no long-term complications with this medication.

If you are prescribed thyroid hormone medication, it may take several months to adjust the dose to your correct individual level. Therefore, you will generally be asked to return to your doctor for follow-up physical examination at about 3 months and 6 months to determine whether or not your thyroid nodule has changed. If the nodule has grown larger, thyroid surgery is usually recommended to remove it in order to exclude a thyroid cancer. If the nodule has disappeared completely, the thyroid hormone medication is slowly decreased to zero and the thyroid gland is examined at about three to six month intervals to make certain that the nodule does not reappear (requiring restarting the medication). If the nodule is the same size or slightly smaller, the medication may be continued for months or years.

It is important to note that although we understand that thyroid hormone medication shrinks some thyroid nodules, its effect on the rest of the gland is not completely understood. Research suggests that thyroid hormone medication may prevent new nodules from forming.