Benign Neoplasm of Thyroid Gland

Most lumps found in the thyroid gland are not cancerous. These benign growths, called thyroid nodules or thyroid adenomas, are very common and usually don’t cause any symptoms, though they can sometimes grow large enough to affect breathing or swallowing.

Table of contents

• What Are Thyroid Nodules?
• Associated Anatomy
• How Common Are Thyroid Nodules?
• Symptoms
• Causes and Risk Factors
• Diagnosis and Testing
• Treatment Options
• Outlook

What Are Thyroid Nodules?

A thyroid nodule is an unusual lump or growth of cells on your thyroid gland^[1]. These lumps can be solid or filled with fluid^[2]. Thyroid adenomas are benign (noncancerous) lesions of the thyroid gland^[3]. There are two main types: follicular and papillary^[3].

More than 90% of detected nodules in adults are noncancerous, but they may represent thyroid cancer in approximately 4.0% to 6.5% of cases^[1]. Most patients are 25 to 65 years of age when first diagnosed^[5]. Thyroid nodules are classified as solitary (a single nodule), multiple (more than one nodule), cystic (fluid-filled), or solid^[1].

Associated Anatomy

• Thyroid gland
• Neck

Your thyroid gland is a small, butterfly-shaped endocrine gland (a gland that makes hormones) located in your neck, below your Adam’s apple^[1]. The thyroid is located at the base of the neck, just above the breastbone^[2]. It produces the hormones thyroxine (also called T4) and triiodothyronine (also called T3), which play a role in metabolism, body temperature, mood, pulse and heart rate, and digestion^[1].

How Common Are Thyroid Nodules?

Thyroid nodules are very common. Healthcare providers detect them in approximately 5% to 7% of adults during a physical examination. Ultrasound imaging (a test using sound waves to create pictures) reveals that 20% to 76% of adults have thyroid nodules^[1]. Thyroid nodules can be detected by ultrasonography in up to 68% of the general population^[14].

Around 80 percent of adults will have at least one thyroid nodule by the time they reach 70 years of age. Approximately 90 to 95 percent of all nodules are found to be benign^[5]. Most thyroid nodules are not cancer and don’t cause problems^[2]. Thyroid nodules are less common in children^[1].

Thyroid nodules are four times more common in women than in men, and their prevalence increases with age^[1]. In two autopsy studies, the incidence of thyroid adenomas was 3% and 4.3%, respectively^[3].

Symptoms

Most thyroid nodules don’t cause symptoms^[1][2]. Often, thyroid nodules are discovered incidentally during a routine physical examination or on imaging tests done for completely unrelated reasons^[7]. They are typically found when a healthcare professional performs an exam of the neck^[2].

However, if you have several nodules or large nodules, you may be able to see them^[1]. Some nodules get so large that they can be felt or seen, often as a swelling at the base of the neck^[2]. In rare cases, nodules can grow big enough to cause symptoms like:

• Trouble with swallowing or breathing^[1]
• Hoarseness or voice changes^[1]
• Pain in the front of your neck^[1]
• Enlargement of your thyroid gland, called a goiter^[1]

If a nodule is large enough to compress the windpipe or tube that connects the throat to the stomach (called the esophagus), it may cause difficulty with breathing, swallowing, or cause a “tickle in the throat”^[7].

Some thyroid nodules may be active in producing thyroid hormones. In such cases, they may be referred to as toxic thyroid adenomas^[3]. Hyperfunctioning thyroid nodules can lead to overproduction of thyroid hormones, also known as hyperthyroidism. Symptoms of hyperthyroidism include rapid heartbeat, feeling shaky or nervous, weight loss, increased appetite, diarrhea and more frequent bowel movements, difficulty sleeping, enlarged thyroid gland, and light or missed menstrual periods^[1]. Some nodules can make too much of a hormone called thyroxine, causing unexplained weight loss, increased sweating, tremor, feeling nervous, and rapid or irregular heartbeat^[2].

Thyroid nodules may also be associated with low thyroid hormone levels, called hypothyroidism. Symptoms of hypothyroidism include fatigue, numbness and tingling in your hands, weight gain, dry coarse skin and hair, constipation, depression, and frequent heavy menstrual periods^[1].

Causes and Risk Factors

Researchers don’t know why most thyroid nodules form^[1]. Most thyroid adenomas are sporadic and not hereditary^[3]. However, some environmental and genetic factors are associated with the presence of a thyroid adenoma.

Iodine deficiency is a well-known environmental risk factor accused of causing the development of a thyroid adenoma, and it is the most common reason for the development of thyroid nodules around the world, especially in underdeveloped countries^[3]. Thyroid nodules occur more often in people who live in countries where food isn’t fortified with iodine, as iodine is necessary for your thyroid gland to make hormones^[1].

In addition, rare genetic mutations in BRAF, RET, KRAS, and genetic rearrangement of the PAX8-PPAR gene are strongly associated with the development of thyroid adenomas^[3].

Other factors that lead to an increased risk of thyroid nodules include:

• History of thyroid radiation^[1]
• Family history of thyroid nodules or thyroid cancer^[1]
• Increasing age^[1]
• Being female (four times more common in women than men)^[1]
• Iron-deficiency anemia^[1]
• Smoking^[1]
• Obesity^[1]
• Metabolic syndrome^[1]
• Alcohol consumption^[1]
• Increased levels of insulin-like growth factor-1 (a hormone)^[1]

Diagnosis and Testing

The first step in diagnosing a thyroid nodule is a physical exam of the neck area^[5]. Your healthcare professional checks the lump or nodule in your neck to rule out cancer and to make sure your thyroid is working as it should^[10].

After thyroid ultrasonography has been performed, the next step is measurement of serum thyroid-stimulating hormone (TSH). If levels are low, a radionuclide thyroid uptake scan is indicated^[14]. Hyperfunctioning nodules are rarely malignant and do not require tissue sampling^[14].

Tests might include:

• Thyroid function tests: These tests measure blood levels of thyroid-stimulating hormone (TSH) and hormones your thyroid gland makes. These tests can show if you have too much or too little thyroid hormone^[10].
• Ultrasound: This test uses sound waves to make images of your thyroid gland. A thyroid ultrasound shows the shape and structure of nodules^[10]. Ultrasound imaging is performed in all patients with thyroid nodules^[14].
• Fine-needle aspiration biopsy (FNA): A biopsy of nodules can make sure there’s no cancer. During the procedure, a healthcare professional puts a very thin needle in the nodule and removes a sample of cells. Ultrasound imaging might guide the needle. The biopsy most often is done in a healthcare professional’s office. It takes about 20 minutes. There are few risks. The samples go to a lab for study under a microscope^[10]. FNA is the most cost-effective and accurate method of obtaining a biopsy sample^[5]. Nonfunctioning nodules and nodules in a patient with a normal or high thyroid-stimulating hormone level may require fine-needle aspiration based on ultrasound characteristics and size^[14]. Nodules with suspicious features and solid hypoechoic nodules 1 cm or larger require aspiration^[14].
• Thyroid scan: A thyroid scan tells more about the thyroid nodules. During this test, radioactive iodine is put into a vein in your arm. You then lie on a table while a special camera makes an image of your thyroid on a computer screen. Nodules that make too much thyroid hormone, called hot nodules, show up on the scan. They take up more of the iodine than typical thyroid tissue does. Hot nodules are rarely cancer. Some nodules take up less of the iodine. They’re called cold nodules. They can be cancer. But a thyroid scan can’t tell which cold nodules are cancer and which are not^[10].

The Bethesda System (categories 1 through 6) is used to classify samples from fine-needle aspiration. Molecular testing can be used to guide treatment when aspiration yields an indeterminate result. Molecular testing detects mutations associated with thyroid cancer and can help inform decisions about surgical excision versus continued ultrasound monitoring^[14].

Treatment Options

Treatment depends on the type of thyroid nodule you have^[10].

Treatment for Benign Thyroid Nodules

Watchful waiting (observation): If the biopsy suggests that the thyroid nodule is benign, the doctor may suggest simply watching the patient and the thyroid nodule. This means having a physical exam and thyroid function tests regularly. Observation usually implies repeating thyroid blood tests, ultrasound, and physical examination in approximately one year. If the thyroid nodule should increase in size or establish symptoms, repeat biopsy or another intervention may be indicated. Thyroid nodules that don’t change over a period of years may never require any treatment whatsoever^[10][12].

Thyroid hormone therapy: Although there is little to no evidence to support that taking thyroid hormone affects the growth of benign thyroid nodules, the practice of prescribing thyroid hormone for benign thyroid nodules continues. In theory, prescribing thyroid hormone can lower the thyroid stimulating hormone (TSH) production of the pituitary gland and thus decrease the stimulation to growth of thyroid tissue^[12].

Surgery: Sometimes clearly benign thyroid nodules are managed with surgery. Some potential indications for removing benign thyroid nodules include when the nodule is large (producing a visible mass in the neck), producing symptoms on the breathing tube or swallowing tube, producing excessive thyroid hormone, or when nodules have indeterminate or suspicious biopsy results^[12]. As thyroid nodule size increases, the need for surgery does as well. When the thyroid nodule reaches 4 cm or greater, it will almost certainly require surgical treatment^[9]. Any nodule that is 4 cm or larger should be removed with thyroid surgery^[9].

Radiofrequency ablation (RFA): In some circumstances, clearly benign thyroid nodules which are symptomatic can be managed with a process called radio frequency ablation. In this procedure, a thin electrode or needle is inserted into the nodule under local anesthetic. Ultrasound is used to guide it into position. The needle sends out an alternating current at the frequency of radio waves that heats the nodule to destroy it. This is known as ablation. The aim is to shrink the nodule to relieve symptoms and improve appearance^[16]. If RFA is used to treat a clearly benign thyroid nodule, either general anesthesia or at times, local anesthesia can be utilized. RFA can work for some benign nodules but may require a period of time for the nodule to get smaller^[12]. After radiofrequency ablation, the nodule volume decreases significantly^[13]. Not all nodules are suitable for RFA treatment. This depends on many factors including size, location, the appearance of nodules, and the symptoms being treated^[16].

Ethanol ablation: This is used as a non-surgical treatment usually for cystic (pure cyst) or predominantly cystic benign thyroid nodules. This involves draining the cyst of fluid under ultrasound guidance then injecting ethanol immediately back into it. It causes the walls of the cyst to stick together and it stops the cyst from recurring. It can be quite effective in shrinking large cysts^[16].

A study comparing surgery with radiofrequency ablation for benign thyroid nodules found that surgical resection and ablation were both effective, but ablation had fewer complications and fewer hospital days^[13]. The incidence of complications was significantly higher from surgery than from radiofrequency ablation (6.0% versus 1.0%)^[13]. Hypothyroidism was detected in 71.5% of patients after surgery but in none following radiofrequency ablation^[13].

Outlook

In most cases, thyroid nodules aren’t a cause for concern^[1]. Even though the vast majority of thyroid nodules are benign, some thyroid nodules do contain thyroid cancer. For this reason, you should see your healthcare provider so they can evaluate the nodule to be sure it’s benign. As with all cancer, the earlier it can be diagnosed and treated, the better^[1].

Of all thyroid nodules discovered, only about 5 percent are cancerous, and under 3 percent of those result in fatalities^[5]. Most thyroid cancer can be cured with appropriate treatment^[6].