Finding a Thyroid Nodule
Single thyroid nodules are usually one of three things: a cyst, which is a growth that contains ﬂuid; a benign tumor or adenoma, which is a growth that contains abnormal, noncancerous cells; or a carcinoma, which is a growth that contains abnormal, cancerous cells. As already mentioned, cysts are frequently benign, and the majority of thyroid nodules are also benign.
Most thyroid nodules are discovered as obvious nodules in the lower front of the neck, seen by the person or by a friend or family member.
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A physician may also ﬁnd a nodule during a physical examination. A complaint of a sore throat, for example, usually completely unrelated to the nodule, may prompt such an exam, resulting in the nodule being found by accident. In addition, if you were exposed to radiation therapy to your neck during childhood, you are at risk for developing thyroid cancer. In this case, you should have regular thyroid exams to detect thyroid nodules that could be cancerous. You can also do your own thyroid self-exam.
When investigating a thyroid nodule, size matters! For that reason, a nodule with the size of 1.0 cm (0.4 in.) in diameter or less is considered too small to be signiﬁcant and usually does not need further evaluation.
Evaluating a Nodule
There are three crucial tests to properly evaluate a thyroid nodule.
The ﬁrst is a TSH test, and the second is an ultrasound imaging test to determine the size of the nodule. The third is a ﬁne needle aspiration (FNA), which draws cells and ﬂuids from the nodule for evaluation by a pathologist.
The TSH Test: Why You Need One
The TSH test will immediately tell you whether your nodule is an autonomous toxic nodule (ATN). It cannot be an ATN if your TSH level is not suppressed (under 0.2). Furthermore, if your TSH level is suppressed, it can save you from having to have an FNA; the only type of nodule that can be treated without the need for a biopsy is an ATN because it is very unlikely to be cancer. Any other thyroid nodule that is larger than 1.0 cm (0.4 in.) in diameter requires an FNA biopsy.
Thus, the diagnostic course is set by the TSH test. If the TSH is low (less than 0.2), then the next step is a radioactive iodine thyroid scan. This scan will show whether the nodule you’ve discovered is hot, meaning that it sucks up most of the radioactive iodine. If it is a hot nodule, then a biopsy is not needed and you can be reasonably conﬁdent that this is an ATN. If the rest of the thyroid is hot but the nodule is not hot, then the nodule should be biopsied.
This situation could be seen if a person has Graves’ disease as well as a thyroid nodule. In this case, the nodule could be benign (colloid nodule or cyst), or it could be a thyroid cancer, although this would be rare. If it were malignant, then surgical removal of the entire gland would be appropriate for both the Graves’ disease and the cancer. The best test to ascertain the nature of the nodule in this situation is a ﬁne needle aspiration biopsy
Ultrasound: Sizing up the Situation
An ultrasound is a device that uses high-frequency sound waves to produce an echo picture of structures in your body. It is the same type of machine used to look at a fetus within a mother’s womb. A jelly lubricant is smeared on the neck to allow the ultrasound transducer to slide easily over your skin. The picture produced by the ultrasound machine produces an excellent image of the thyroid gland so that any nodules or masses can be assessed and measured. A ﬁne needle biopsy can be performed during the ultrasound to obtain samples of cells from the nodule or mass, permitting the physician to ﬁnd out whether it is malignant.
Although most thyroid nodules can be biopsied by a skilled physician without an ultrasound, sometimes thyroid nodules are discovered accidentally while performing an ultrasound evaluation of the carotid arteries and the nodule can only be found with the ultrasound.
A major problem with thyroid ultrasound evaluations is that these devices are much too sensitive. Most people can be shown to have very tiny thyroid nodules using a thyroid ultrasound. When a physical examination is used to ﬁnd thyroid nodules to evaluate for possible cancer, only large and clinically signiﬁcant nodules (usually greater than 1.0 cm in diameter) can be found. These types of nodules have a 10 percent chance of being malignant and so warrant a biopsy.
Should Ultrasounds Be Used to Screen for Thyroid Nodules?
Very tiny nodules are found in nearly all people during ultrasound exams. Since these tiny nodules have such a small chance of being anything to worry about, it’s just not feasible to check them out in everybody. For this reason, thyroid ultrasounds should not be used to screen for thyroid nodules in most people because you’ll almost always ﬁnd them. The only population that warrants screening is the population that has been exposed to radiation in the neck or exposed to fallout from nuclear testing. People with a history of childhood exposure to radiation therapy in the neck region or to radiation fallout from nuclear testing are three times more likely to develop thyroid cancer than those in the general population, so ﬁnding nodules in these people could help to ﬁnd early thyroid cancers.
Fine Needle Aspiration Biopsy: The Gold Standard
Fine needle aspiration has changed the way thyroid nodules are biopsied and evaluated. Thirty years ago, thyroid nodules were usually tested with a radioactive iodine scan without a TSH test to see if the nodule was hot or cold. Painful core biopsies, using a thick needle, were also used.
FNA has changed all that. FNA, a twenty-minute procedure, is usually very accurate. It can be performed in a doctor’s ofﬁce and is as simple as drawing a blood sample. It is considered the gold standard for evaluating a thyroid nodule. Studies have shown that because of FNA, cases of thyroid surgery have dropped by 50 percent. This means that many people can be spared “look-see” surgery, which used to be done frequently when cancer was suspected.
Before an FNA, the skin around your nodule is cleansed with antiseptic. The needle, which is thinner than the standard needles used to sample blood, needs to be inserted three to six times to obtain a good sample. This is known as obtaining passes and means that each nodule is aspirated in different areas and in different directions.
If you have several nodules, they’ll each need to be aspirated with the appropriate number of passes, and greater attention will be paid to larger nodules. The needle will aspirate, or draw out, cells and/or ﬂuid, which are sent off to a pathologist to determine whether the nodule is benign or malignant.
Once the aspiration is done, you’ll get a bandage on the puncture site and then go home. You may have some neck tenderness or mild swelling afterward, but that will subside within twenty-four hours.
If you develop a fever or notice the puncture site is black and blue or bleeding, call your doctor. This may mean that you have a broken blood vessel or an infection at the puncture site.
Like many diagnostic procedures used to detect cancer, including Pap smears and mammograms, FNA is not 100 percent accurate. Any physician, including endocrinologists, internists, surgeons, pathologists, and radiologists, can perform FNAs if they’re trained in the procedure. But ﬁne needle aspiration is not an exact science. Much depends on the skill of the doctor performing the FNA, his or her ability to obtain an adequate specimen of the right area, and the experience of the pathologist reading the slide that contains the smear. As a result, there are often inconclusive or unsatisfactory results.
A result that’s inconclusive means that there’s no way for the pathologist to tell whether the nodule is benign or malignant. This happens about 10 to 15 percent of the time. In these cases, the slides are sometimes sent to a pathologist or cytologist who has more experience in interpreting cells. He or she can review the slides as well as interpret them. The other options in these cases are either to wait and repeat the FNA or to go directly to surgery, depending upon the size and characteristics of the nodule. An unsatisfactory result, which happens 1 to 10 percent of the time, means that the FNA procedure was not successful in obtaining enough thyroid cells for the pathologist to make a diagnosis. In this case, the FNA may need to be repeated.
Other common pathology errors include:
• Calling tissue malignant when it’s benign. This is called a false positive.
• Calling tissue benign when it’s malignant. This is called a false negative.
• Identifying the malignant tumor correctly, but not classifying it as the right cell type or grade.
• Calling inadequate FNA samples benign because no cancer cells are seen. To be considered benign, the slides must contain sufﬁcient numbers of noncancerous thyroid cells.
Since pathology errors are common, a second opinion is advised when cancer is in question.
Conﬁrming a Pathology Report
The only way to conﬁrm a cancer diagnosis is through a biopsy of the tissue. If you receive news that your nodule is (or might be) cancerous, make sure to get a second pathologist with equal or more experience to review the biopsy slides and provide an independent, separate opinion.