Carcinoma

 

Management of a Thyroid Nodule

by Joel I. Hamburger, MD
Consultant to the Department of Surgery,
Sinai Hospital of Detroit, Southfield, MI (see also Thyroid Patient Guides on Thyroid Disease – Thyroid Cancer)

It has been said that if you had to have cancer, and if you had your choice, thyroid cancer should be high on your list because the cure rate is so excellent. Therefore, if you or your doctor discover a nodule (lump) in your thyroid gland don’t panic. Thyroid nodules are very common, but only about 5% of them contain cancer, and more than 90% of thyroid cancers are curable.

To be sure to help yourself the most, follow your doctor’s recommendations for the evaluation of your nodule to determine whether it is one of the 95% that are benign (harmless), or one of the 5% that are malignant.

BLOOD TESTS MEASURE THYROID FUNCTION
Here is what usually happens during an evaluation of a thyroid nodule: first you will have an examination and blood tests to determine whether the overall output of thyroid hormone is normal, increased, or decreased. Normal results are usually obtained, because thyroid nodules usually do not produce thyroid hormone, and also do not interfere with the function of the rest of the thyroid gland. Those few nodules that do actively produce thyroid hormone without regard to the body’s needs are called autonomous nodules. Patients with these nodules may become hyperthyroid if the blood level of thyroid rises above normal. These nodules are nearly always harmless.

On the other hand, sometimes nodules develop in thyroid glands that do not produce normal amounts of thyroid hormone, and blood levels of thyroid hormone in such patients may therefore be low. A very common condition in which this occurs is chronic thyroiditis. The disorder is also known as Hashimoto’s thyroiditis in honour of the Japanese physician who first described it in 1912. In this condition, antibodies directed against the thyroid appear in the body, and often can be detected in the blood. Although a nodule in a patient with Hashimoto’s thyroiditis is probably part of the thyroiditis, thyroid cancers are sometimes seen in these patients, so further study of such a nodule usually is necessary.

A very uncommon form of thyroid cancer, medullary cancer, produces a substance called calcitonin. Blood tests can detect calcitonin, sometimes even before these nodules can be felt. Since medullary thyroid cancer often runs in families, the calcitonin test can be done to make the diagnosis early when the disease is highly curable. However since this disorder is uncommon, serum calcitonin is checked routinely only when there is a family history of this type of thyroid cancer.

THYROID SCAN MAY HELP
An important and widely used initial screening test for thyroid nodules is the thyroid scan. If you have a thyroid scan, you will be given a tiny amount of radioactive material that is taken up by your thyroid. Imaging machines detect the radioactivity and record it on film to produce a picture showing the distribution of the radioactivity in your thyroid. Thyroid nodules may show up on scanning as zones of decreased activity (“cold” nodules) or zones of increased activity (“hot” nodules). Hot nodules almost never contain cancer.

Most cold nodules are also harmless, but since thyroid cancers usually appear as cold nodules as well, all cold nodules require further study. Some physicians advise an ultrasound test to determine whether a cold nodule is solid (as are most tumors whether or not they contain cancer) or a fluid-filled cyst. Ultrasound studies are being ordered less and less often, because needle biopsy will provide the same information, and also can provide cells and tiny tissue fragments for microscopic study by pathologists.

NEEDLE BIOPSY
Needle biopsy may sound frightening, but a local anesthetic is used, so that usually you will not have much pain, only a sensation of pressure or mild discomfort. Needle biopsies are of two basic types. If you are to have a fine needle biopsy, the physician doing it will use a very thin needle to withdraw thyroid cells. Ordinarily, several samples are taken from different parts of the nodule to ensure that the nodule has been studied thoroughly. Since large needle biopsy is done with a bigger needle that can take a core of tissue from the nodule, these larger tissue samples are easier for most pathologists to interpret. However, the fine needle biopsy which is simpler and produces less discomfort is the more commonly performed biopsy procedure.

It takes a few days to obtain the final report from the pathologist who examines the biopsy specimens. The report will usually indicate one of the following findings:

1. The nodule is benign (not cancer). This is the result obtained in approximately two-thirds of patients from whom enough tissue has been obtained in the biopsy test. Moreover this diagnosis by an experienced pathologist is highly reliable. The risk of overlooking a cancer is generally less than 5%, and less than 1% in medical centres with the most experience. Generally, these nodules need not be removed. Instead, your doctor may recommend treatment with thyroid hormone in an attempt to shrink the nodule, or at least prevent further growth. If the nodule fails to shrink, or enlarges during treatment, the biopsy can be repeated or the nodule removed surgically. The pathologist’s diagnosis at surgery is almost always the same as that obtained from the needle biopsy. Even when enlargement of a nodule does occur, it is more likely to be caused by inner bleeding, degeneration, or inflammation than by malignancy.
2. The nodule is malignant (cancer). In my practice about 10% of nodules from which needle biopsy produces specimens adequate for diagnosis are malignant. Such nodules should be removed. Definite or highly suspicious findings of malignancy are nearly always confirmed at surgery. The extent of the operation performed depends upon the type of cancer, the extent of disease determined by tests before the operation, and also the findings during surgery.
3. The specimen is inadequate to make any diagnosis. Pathologists experienced with needle biopsy work tend to be very fussy about making diagnoses unless they are confident that sampling of the nodule has been adequate. Some thyroid nodules are composed of dense fibrous tissue, or have undergone such extensive degeneration that recognizable thyroid tissue cannot be obtained. In this situation it is usually best to repeat the biopsy. Other nodules are too small or too deep in the neck to permit needle biopsy. If an adequate specimen cannot be obtained, or if another needle biopsy is impractical, the decision to operate or just observe a thyroid nodule may be based on the physician’s experience in evaluating nodules, the physical examination, and the test described above. In some cases your physician may decide to treat you with thyroid hormone for three to six months or longer in the hope that this treatment will cause the nodule to disappear, or at least to shrink as evidence that your nodule is harmless. If it does not get smaller, but instead enlarges, your physician is likely to recommend removal of the nodule in an operation.
4. The biopsy specimen contains sizable amounts of thyroid cells or tissue, but the microscopic findings permit neither the diagnosis nor exclusion of thyroid cancer. About 18% of nodules for which needle biopsy produces specimens thought to be adequate for diagnosis have these inconclusive findings. The only way to establish a diagnosis on these nodules is to remove them surgically and carefully study them microscopically, looking for signs of malignancy. Still, most of these nodules (about 90%) are benign.Diagnosis and management of thyroid nodules require skill and experience on the part of all physicians who participate in the evaluation. Needle biopsy has greatly improved the accuracy of diagnosis. In my clinic, the proportion of nodule patients for whom surgery is advised has been reduced significantly and, at the same time, a number of cancers that otherwise might have been overlooked have been identified and promptly treated.

Above all, if you think you have a lump in your thyroid, have it checked by your doctor. Most nodules are benign and cared for easily. But even those that do turn out to contain cancer are unlikely to develop into a life-threatening problem, since most thyroid cancers are curable. However, the earlier the treatment is given, the better the result will be for you.

(Dr. Hamburger is author of The Thyroid Gland: A Book for Thyroid Patients)

Copyright ©Thyroid Foundation of Canada/La Fondation canadienne de la Thyroïde.
Originally published in The Bridge, Vol. 1, No. 1.
Reprinted from Thyrobulletin, Vol. 7, No. 4.

Reviewed 2000