Thyroid Nodules

Thyroid nodules are small lumps of abnormal tissue within the thyroid gland.

Thyroid nodules are more common among older people than among younger people. In most cases, the cause of thyroid nodules is unknown. The only known cause is radiation treatments to the neck during childhood. The vast majority of thyroid nodules are noncancerous (benign). However, because thyroid cancer usually begins as a nodule in the gland, each nodule must be examined to ensure that it is not cancerous (malignant).

Nodules vary in their composition and in whether they produce thyroid hormone. One or many nodules may gradually develop. When many nodules develop, the condition is called a multinodular goiter. If many nodules have developed and hyperthyroidism occurs, the condition is called toxic multinodular goiter.

Symptoms and Diagnosis

Some people notice a painless swelling in the front part of their neck. More often, the swelling is not noticeable, and the doctor feels (palpates) the thyroid gland and finds one or more nodules. In some cases, a nodule is found when a person undergoes an ultrasound scan of the carotid arteries or a computed tomography (CT) or magnetic resonance imaging (MRI) scan of the neck or chest for another medical condition.

An ultrasound scan may also be performed to determine the composition of the nodule. Nodules may be solid or partially or completely filled with fluid (in which case they are cysts). The likelihood of a nodule being cancerous is lowest if the nodule is completely filled with fluid. Partially fluid-filled and solid nodules have a higher chance of being cancerous. But the vast majority of nodules are not cancerous. Blood tests are performed to determine whether hypothyroidism or hyperthyroidism is present, but usually the person has normal thyroid function.

Doctors describe nodules as hot or cold: These labels do not refer to temperature, but to how the nodules appear on a radioactive thyroid scan. Hot nodules take up the radioactive material (iodine or technetium) and secrete thyroid hormones. Such nodules may cause hyperthyroidism. Hot nodules are noncancerous. Cold nodules do not take up the radioactive material and do not secrete thyroid hormones. Cold nodules are more likely to be cancerous, although most (95%) are noncancerous.

Most often, a sample of tissue from the nodule is removed through a small needle and examined under a microscope. This procedure is called a fine-needle aspiration biopsy. A biopsy is usually needed to determine whether a nodule is cancerous. The procedure is usually performed in the doctor's office and takes 20 minutes or less. If the nodule is difficult to feel, the biopsy may be done using ultrasound to guide the needle. A local anesthetic is usually used to numb the neck where the needle is inserted.

Treatment and Outlook

Treatment of noncancerous nodules depends on the cause and on the symptoms they produce. Nodules that secrete too much thyroid hormone may produce hyperthyroidism, which requires treatment, usually with radioactive iodine. Noncancerous nodules that do not secrete thyroid hormones usually do not require treatment. If the nodules cause discomfort or are cosmetically displeasing, they can be removed surgically.

Thyroid cancer can almost always be treated and cured: Most people with thyroid cancer are still alive 20 years after the cancer is detected. A few rare types of thyroid cancer, particularly anaplastic thyroid carcinoma and thyroid lymphoma, have a poorer outlook.

If tests suggest or confirm that a nodule is cancerous, surgery is performed to remove as much of the gland as possible. After surgery, radioactive iodine is usually given to destroy any remaining thyroid tissue. Once a person's thyroid gland has been removed or destroyed, treatment with thyroid hormone must continue for life.