What is Thyroid Nodule?
The American Thyroid Association explains that a thyroid nodule is a unique growth found in the thyroid gland. It’s different from the rest of the thyroid tissue and can be seen using specific types of medical imaging. These nodules can be solitary or multiple, filled with fluid (cystic), or solid.
Thyroid nodules are quite common. When doctors do a physical examination, they find these nodules in about 5 – 7% of adults. But, studies have shown that in people who died from other causes and were never diagnosed with thyroid disease, 50% had thyroid nodules larger than one centimeter. The reason we’re finding more nodules nowadays is due to advanced imaging methods including ultrasound, CT scans, MRI, and PET scans.
It’s important to note that over 90% of these nodules are typically not harmful, but they are still clinically significant. This is because, in about 4.0% to 6.5% of cases, these nodules can represent thyroid cancer.
What Causes Thyroid Nodule?
Thyroid nodules, which are small lumps that form in your thyroid gland, can be linked to a wide range of conditions. These can vary from harmless to potentially serious issues that can progress slowly or very quickly.
About 23% of singular thyroid nodules are actually the largest nodule within a greater number of smaller ones, a condition known as a multinodular goiter.
Exposure to radiation significantly increases the chances of both harmless and harmful thyroid nodules, with this group developing nodules at a rate of about 2% each year. In fact, nodules in previously irradiated thyroid glands can be cancerous in 20% to 50% of cases.
Smoking, being overweight, metabolic syndrome, drinking alcohol, high levels of a hormone called insulin-like growth factor-1, and uterine fibroids also increase the risk of thyroid nodules and goiter, which is a swollen thyroid gland. Conversely, birth control pills and certain cholesterol-lowering drugs, called statins, may reduce the risk.
Thyroid nodules can be categorized into neoplastic, which means they could be harmless or cancerous, and non-neoplastic. Neoplastic nodules cover non-functioning and functioning nodules, while non-neoplastic nodules cover hyperplastic and inflammatory nodules, which are related to overgrowth and inflammation.
Colloid nodules, which are noncancerous growths, are the most common type of thyroid nodules and do not have a higher risk of becoming cancerous. However, most follicular adenomas, another type of noncancerous growth, have similar traits to follicular carcinomas, which are a type of thyroid cancer.
Thyroid cancers can be divided into non-medullary thyroid cancers, which make up about 95% of all thyroid cancer cases and come from epithelial cells, and medullary thyroid cancer, which comes from thyroid cells that produce the hormone calcitonin. About 20% of medullary thyroid cancers are inherited and can occur as part of syndromes involving multiple endocrine neoplasia, which is a group of disorders that affect your endocrine system.
Risk Factors and Frequency for Thyroid Nodule
The likelihood of developing thyroid nodules varies depending on factors like the method of screening used, the population being examined, age, gender, iron levels, and exposure to thyroid radiation. For example, the risk is greater as people get older, among women, those with low iron levels, and people who’ve had thyroid radiation. People who have received hematopoietic stem cell transplantation also have a significantly higher likelihood of developing secondary thyroid cancer.
When doctors examine adults, they find thyroid nodules in about 5% to 7% of cases if they’re using a physical examination. However, this percentage increases to 20% to 76% if an ultrasound is used, a finding that aligns with autopsy results.
Thyroid nodules are roughly four times more prevalent in women compared to men, and more common in people living in areas with low iodine levels.
- Thyroid nodules occur more frequently in iodine-deficient areas.
- A study that tracked patients over 20 years estimated that about 0.8% of men and 5.3% of women have thyroid nodules.
- Men are twice as likely to have thyroid cancer compared to women, with rates of 8% vs 4% respectively.
Signs and Symptoms of Thyroid Nodule
Most people with thyroid nodules may notice a large lump at the front of their neck. Sometimes, these nodules are found during imaging tests done for other reasons. Typically, these nodules don’t cause symptoms, and over 99% of them don’t lead to thyroid disease. However, some people may experience a feeling of pressure or pain in the neck, especially if the nodule is bleeding internally.
Doctors can feel for thyroid nodules by touching the neck, but this method can only detect 4% to 7% of cases. Suspicious signs of a malignant (cancerous) nodule can include a large size (more than 4 cm carries roughly a 19% risk of malignancy), hardness, adherence to surrounding tissues, swollen neck lymph nodes, and vocal cord paralysis. However, physical check-ups might not always be effective, depending on the individual’s body type.
If a lump is found alone or along with swollen lymph nodes (bigger than 1 cm) and vocal cord paralysis, there is almost certainly (100% chance) a thyroid cancer. Moreover, knowing a patient’s societal background is crucial as some patients, particularly those with Multiple Endocrine Neoplasia II syndrome, are at an increased risk for a particular type of adrenal gland tumor (pheochromocytomas) and require further tests before any surgery.
Testing for Thyroid Nodule
If you have a lump or nodule in your thyroid, the first step will be to have an examination and a history check, a thyroid-stimulating hormone (TSH) level check, and a thyroid ultrasound. TSH is a substance in your body that regulates the thyroid. The level of TSH can help find any subtle issues with thyroid function.
Your doctor will follow this up with more tests, which may consist of blood tests, a fine-needle aspiration (FNA), genetic markers, substance identifiers in your body known as immunohistochemical markers, and several imaging tests. These tests could include ultrasound, elastography, MRI, CT, or 18FDG-PET scans.
When dealing with a thyroid nodule, the first test is usually the TSH measurement. This can guide the doctor on how to proceed next. A normal or high TSH level can be concerning because the risk of cancer tends to rise with the level of TSH, while a low TSH level usually indicates a harmless nodule. If the TSH is low, your doctor will consider the chance of the nodule acting independently using a 123-I or pertechnetate scintigraphy scan. These are types of imaging tests. It’s important to note that these independent nodules are usually harmless and often don’t need more tests.
The ultrasound of the thyroid is an important test used to evaluate thyroid nodules. It can show the doctor the size, structure, and changes in the tissue and can detect lesions as small as 2 mm. It is frequently used to distinguish harmless from harmful lesions to avoid unnecessary procedures. Several features, such as tiny calcifications, irregular edges, deep echo-less areas (hypoechogenicity), being taller than wide, and increased blood flow could be associated with cancer.
Ultrasound is good at finding small thyroid nodules that cannot be felt. However, the clinical importance of these tiny nodules is often uncertain. In a study, 24% of the incidental thyroid nodules in patients who were previously diagnosed with a non-thyroid primary cancer turned out to be cancerous. This rate is much higher compared to the 5% cancer rate expected in patients without another known primary tumor.
In addition to ultrasound, fine-needle aspiration (FNA) is a major tool for assessing thyroid nodules. It’s the most cost-effective diagnostic tool as it provides valuable information about the cells within the nodule. An ultrasound-guided FNA is often preferred as it is less likely to lead to false negatives and uncertain results compared to biopsies guided by touch alone.
The decision to have an FNA might depend on the patient’s medical history, clinical and ultrasound findings. Nodules that are smaller than one centimeter are usually biopsied when there is more than one suspicious ultrasound feature, neck lymph node swellings, or a high risk in their medical history. Otherwise, a cutoff size of 1 centimeter is used for solid nodules with only one suspicious ultrasound feature.
FNA is suggested for:
– Non-palpable thyroid nodules larger than 1 cm
– Palpable nodules smaller than 1.5 cm
– Deeply located nodules
– Nodules near blood vessels
– Nodules that had a previous inconclusive FNA cytology result
– Mixed or cystic nodules after an inconclusive standard FNA result
– Additionally, if there are also non-palpable neck lymph node swellings
Cystic or lesions that appear spongy are considered to be at a low risk for being cancerous and are either watched or biopsied if larger than 2 centimeters.
Treatment Options for Thyroid Nodule
How doctors initially handle thyroid nodules depends on the type of lump, certain characteristics seen in ultrasound imagery, and whether the lump is causing the thyroid to overproduce hormones. A procedure called fine-needle aspiration (FNA) is used to sample cells from the lump, and the results of this test will help decide the best treatment method.
The FNA cytology results divide into six major categories according to the Bethesda classification. Each category indicates a different approach for what should be done next:
1. Non-diagnostic: The risk of the lump being cancerous is 5% to 10%. These results are seen as unsatisfactory because there were not enough cells to examine. If not many cell-containing thyroid tissue is obtained, it shouldn’t be interpreted as a negative biopsy. Generally, FNA is repeated in 4 to 6 weeks in these cases.
2. Benign: The risk of cancer is 0% to 3%. Patients with benign nodules, such as macrofollicular nodules, colloid adenomas, nodular goiter, and Hashimoto Thyroiditis, are usually monitored without surgery. Doctors will use an ultrasound to check on the nodules every 12 to 24 months, and maybe less frequently as time goes on. If the ultrasound shows that there’s a high chance of the lump being malignant or cancerous, FNA should be repeated within 12 months despite the initial biopsy showing it was benign.
3. Atypia of undetermined significance or follicular lesion of undetermined significance: Here, the risk of cancer is 10% to 30%. How to deal with these types of nodules varies. Some doctors may request a second FNA sample to run further tests, or repeat the FNA after 6 to 12 weeks. A special type of scan, a radionuclide scan, may be done if the repeat sample shows a different architectural pattern.
4. Follicular neoplasm or suspicion of a follicular neoplasm: The cancer risk is 25% to 40%. The approaches followed for this category will be similar to those outlined for category 3.
5. Suspicious for malignancy: The cancer risk is 50% to 75%. Patients in this category should expect to have surgery as part of their treatment. Molecular marker tests, which look for genetic changes in the sampled cells, should typically not be used for diagnosis in these cases.
6. Malignant: The cancer risk is 97% to 99%. This category includes conditions such as papillary cancer, medullary thyroid cancer (MTC), thyroid lymphoma, anaplastic cancer, and metastasized cancer. Again, surgery is usually the recommended treatment route for patients in this category.
What else can Thyroid Nodule be?
While most lumps and bumps that you find on the front of your neck are likely harmless, like benign thyroid nodules or cysts, there’s still the need to rule out cancer, especially for those with a higher risk of thyroid cancer.
Bodily masses that are present from birth can show up in the front part of the neck. Normally, these are found at birth, but some may only become apparent when a person is an adult. If these masses appear when someone is older, it could be a sign of a possible cancer. Types of cancer, such as those affecting the tongue, tonsil, and thyroid can present as cyst-filled neck masses.
Neck masses that are caused by inflammation are usually a sign of enlarged lymph nodes — the result of a viral or bacterial infection. These are often found to be on top, deep inside, or behind the sternocleidomastoid muscle (one of the larger neck muscles), and in front of the trapezius muscle (a major muscle in the back and neck).
Certain non-thyroid cancer-related diseases might also show up as neck masses. These are most of the time linked with a type of skin cancer known as squamous cell carcinoma that begins in the hollow organs like those of the respiratory system and digestive tract.
What to expect with Thyroid Nodule
Most lumps or growths on the thyroid gland are harmless. However, there are certain signs that make doctors more suspicious of cancer, including a particular blood test result (normal to high levels of a hormone called TSH), exposure to radiation, certain inherited conditions (like multiple endocrine neoplasia), and specific features seen on an ultrasound (like tiny calcium deposits, uneven borders, darker color, unusual shape, and blood flow).
Although a single nodule can have a higher risk of being malignant than one of many nodules in an enlarged thyroid gland, the overall risk is about equal due to the risk attached to each individual nodule in a large gland.
The outcome for thyroid cancer can be quite diverse. It greatly depends on the type and subtype of cancer, as well as individual factors such as the person’s age when diagnosed, size of the tumor, invasion of the tumor into nearby soft tissues, and presence of cancer spread to distant parts of the body.
Most patients with a type of thyroid cancer called papillary thyroid cancer do not die from the disease. According to one study, among patients with papillary thyroid cancer that has not spread elsewhere, 6% died due to the cancer.
Certain factors may increase the chance of cancer coming back or leading to death. These include being male, involvement of lymph nodes in the chest,
delay of more than 1 year in surgical treatment after finding a thyroid nodule, and the presence of multiple foci of cancer within the thyroid gland.
Follicular thyroid cancer, another type of thyroid cancer, generally appears in older people and is more aggressive. It often spreads to distant parts of the body and has a higher death rate than papillary thyroid cancer.
Possible Complications When Diagnosed with Thyroid Nodule
Some individuals with functional thyroid nodules, a noncancerous growth on the thyroid gland, might experience symptoms of hyperthyroidism, an overactive thyroid. These symptoms may include excessive sweating, a rapid heart rate, or difficulty regulating blood sugar levels. However, it’s important to note that most thyroid nodules are not harmful, and many people with them will not experience any symptoms.
A small percentage of individuals might experience thyroid pain. This symptom is particularly common in people with cystic thyroid lesions. If the thyroid is painful, this could indicate sudden bleeding into the tissue or a type of stroke in the thyroid that occurs when tissue dies due to lack of blood supply.
Common Symptoms:
- Hyperthyroidism symptoms
- Excessive sweating
- Rapid heart rate
- Difficulty regulating blood sugar levels
- No symptoms (most commonly)
- Thyroid pain (few cases)
Preventing Thyroid Nodule
Patients should be comforted knowing that up to half of all people have at least one thyroid nodule, and most of these are harmless and caused by non-dangerous conditions. A thyroid nodule is a small lump that forms in your thyroid, a small gland at the base of your neck. Many times, these nodules are found accidentally during routine check-ups or while getting medical imaging for other reasons. It’s important to remember that not all nodules are cause for concern. The importance of these findings varies from person to person, depending on their specific health risks and condition.
