Thyroid Nodule - Symptoms, Causes, and Cancer Risk

The thyroid is a butterfly-shaped gland located in the neck just below the larynx. The main function of the thyroid is to produce hormones that control the metabolism of our body.


Among the various problems that may arise in the thyroid nodule is one of the most common. It is estimated that up to 1/3 of adult women have nodules that can be detected by ultrasonography. The risk of having a thyroid nodule increases over the years. Just to give you an idea, the prevalence of thyroid nodules from the age of 50 is as follows:

• 50% of people over 50 have at least 1 thyroid nodule
• 60% of people over 60 have at least 1 thyroid nodule
• 70% of people over 70 have at least 1 thyroid nodule

Thyroid nodules are bilateral lesions that arise in the thyroid tissue, and can be caused by various conditions, most of them benign. Less than 5% of identified nodules are caused by a malignant disease. This means, therefore, that 95% of thyroid nodules are not cancer.

The so-called nodular thyroid disease may present in several ways, for example: the nodule may be single or there may be multiple nodules scattered throughout the gland, which is called a multinodular goiter; the nodules may be solid or may contain liquids inside (thyroid cyst). If the nodule is large, it may be visible on the neck and cause symptoms such as difficulty swallowing. On the other hand, if the nodule is small, it may go unnoticed for years.

Some nodules acquire functioning independently of the rest of the gland and can produce thyroid hormones in large numbers, causing the signs and symptoms of hyperthyroidism.

Most thyroid nodules are caused by adenomas, which are benign tumors, that is, they are not cancer. Among the most common types of nodules we can mention:

Colloid nodule: benign tumors formed by tissue identical to thyroid tissue. They can be single or multiple.

Follicular adenoma: it is also a type of benign thyroid tumor. Usually solitary, the follicular adenoma can produce thyroid hormones independently, being called in these cases of toxic adenoma.

Thyroid cyst: are the nodules that contain fluid inside. The vast majority of thyroid cysts are benign, but some cysts that show a mixture of solid and liquid material, called complex cysts, may actually be cystic-appearing thyroid cancer.

Inflammatory nodule: is a nodule that develops due to inflammation of the thyroid gland, usually by an episode of thyroiditis. This type of lump also has nothing to do with cancer.

Multicodular goiter: it is a thyroid with multiple nodules, which can vary in size, from a few millimeters to several centimeters. When these multiple nodules are functioning, that is, capable of producing thyroid hormones, we call toxic multinodular goiter (or Plummer's disease), which, after Graves' disease, is the main cause of hyperthyroidism.

Thyroid cancer: They are usually single, solid, well attached thyroid nodules, fast growing and are not hormone producers. There is a common presence of palpable lymph nodes in the neck associated with the malignant nodule.

Most thyroid nodules do not cause symptoms. When they do, there are two reasons:

1. Are functional nodules, that is, nodules that produce too much thyroid hormones, causing the patient to develop signs and symptoms of hyperthyroidism.

2. Are llarge nodules, capable of being noticed when the patient looks in the mirror or being palpated when examining the anterior region of the neck. Large thyroid nodules may also block nearby structures, such as the trachea or the esophagus. The most common symptoms of large nodules are the nuisance to swallow and the sensation of a lump at the base of the neck.

Eventually, thyroid nodules can be painful. But as we have already mentioned, in most cases thyroid nodules are asymptomatic lesions.

Thyroid cancer is also usually asymptomatic. When it causes symptoms, it is usually due to its rapid growth. A large thyroid tumor can cause difficulty in swallowing or breathing and hoarseness. Other common symptoms are weight loss and the presence of lymph nodes in the neck.

Once the thyroid nodule is identified, whether by physical examination or by imaging, the most important step is to determine whether the lesion is a benign or malignant nodule.

Ultrasonography is a good exam to evaluate the appearance of the lump, but it is bad for determining whether it is functioning or not. A nodule suspected to be cancer on ultrasound usually has irregular borders, be hypoechoic (generates little echo), have calcifications and present blood flow. However, these findings are not sufficient to confirm a cancer, and biopsy is always necessary in suspected cases.

Other imaging tests that may be used to investigate a thyroid nodule are computed tomography, thyroid scintigraphy, and PET (positron emission tomography).

Blood TSH, T3, and T4 dosage is important for assessing nodule function. Depending on this result, the investigation takes a different tack. In a simplified way they can say that:

• When TSH is low, this usually indicates a hormone-producing nodule, the next step being a thyroid scintigraphy to confirm that the nodule is active. Functioning nodules are not usually malignant.
• When TSH is high, thyroiditis is likely, and thyroid antibodies are indicated. These cases may be an early stage Hashimoto.
• If TSH is normal, needle puncture is indicated, a procedure that removes a small piece of tissue from the lump for microscopic evaluation. Fine needle aspiration is nothing more than a biopsy that can be done in the office with local anesthetic.

Fine needle aspiration (FNA) may not be conclusive in some cases of cancer, so a good investigation of the nodule is necessary to avoid passing the diagnosis. There are also rare cases where fine needle aspiration may falsely suggest the diagnosis of cancer, requiring removal of the thyroid and reassessment by the pathologist to confirm the absence of malignancy. A famous case occurred a few years ago with the former Argentine president, Cristina Kirchner, who had a provisional diagnosis of thyroid cancer when doing the PAF, but that after the removal of the gland it was verified that there was no malignant lesion.

Treatment of the thyroid nodule depends on the type of nodule that was identified in the investigation. If there is certainty that it is a benign nodule, you do not have to do anything. Only monitoring is indicated.

If the nodule is benign but is producing unwanted hormones, surgery to remove it is indicated. Another option is the irradiation nodule destruction.

Surgery is also indicated when we suspect the lump may be cancer. Currently, most patients with thyroid cancer have a good chance of cure. We'll talk about thyroid cancer in a separate text.