Thyroid nodules

What thyroid nodules are

The thyroid is a small gland at the front of the neck. We define a thyroid nodule as a distinct area within it that looks different from the surrounding tissue on ultrasound, whether solid, fluid-filled (a cyst) or mixed. There may be one or several; when there are several, this is called a multinodular goiter.

Nodules are common. A small share of adults have nodules that can be felt, but ultrasound, which looks in far more detail, finds them in a much larger share, especially after age 50 and in women. In the great majority of cases they are benign, meaning they are not cancer: according to accepted data, cancer is found in about 5–15% of nodules evaluated, and thyroid cancer, when found in time, has a very good outlook. The aim of the evaluation is therefore not to frighten but to tell as accurately as possible the small minority that need treatment from those that can simply be followed.

The causes of nodules vary: areas of abnormal growth of normal tissue (colloid nodules, the most frequent), cysts, benign adenomas, Hashimoto’s thyroiditis and, more rarely, cancer. Iodine deficiency is a known cause in some regions. The chance of nodules rises with age, female sex, a family history of thyroid disease, and radiation to the head or neck, especially in childhood.

Symptoms

Most nodules cause no symptoms at all and are found by chance: during an ultrasound done for another reason, during a neck examination, or when the patient notices or feels a swelling. When they do cause problems, these depend on the size and function of the nodule:

• a visible swelling at the front of the neck;
• a sense of pressure or tightness in the neck, difficulty swallowing or breathing when very large, especially when lying down;
• lasting hoarseness, when the nodule involves the nerve of the voice box (a sign that needs prompt assessment);
• symptoms of hyperthyroidism (fast heartbeat, tremor, weight loss, sweating, nervousness), when the nodule makes hormone itself in excess (a “hot” nodule);
• sudden severe pain, when there is bleeding inside the nodule (common and harmless).

The more worrying signs, which need prompt assessment, are a hard, fixed nodule, growth over weeks or months, persistent hoarseness and enlarged lymph nodes in the neck.

Diagnosis

The evaluation follows a clear sequence:

1. A TSH test. It shows whether the thyroid is working normally. If TSH is low, the nodule may be functioning (“hot”) and the doctor may recommend a thyroid scan at a suitable center; hot nodules are rarely cancer. If TSH is high, hypothyroidism may be the issue (see hypothyroidism).

2. Thyroid ultrasound. This is the main test. It measures the nodule and describes it by features linked to risk: composition (fluid or solid), density (dark or bright), margins (regular or irregular), the presence of microcalcifications, and shape. These features are summarized in a standardized scoring system (such as TI-RADS) that places the nodule in a risk category. Purely cystic nodules and those with a “sponge-like” look have very low risk; solid, hypoechoic nodules with irregular margins or microcalcifications have higher risk. Ultrasound also assesses the lymph nodes of the neck.

3. Fine-needle aspiration (FNA). When the size and ultrasound appearance call for it, a small sample of cells is taken with a very thin needle, usually under ultrasound guidance, then examined under a microscope and classified by the Bethesda system (from benign to suspicious or malignant). Not every nodule needs a biopsy: small nodules with a reassuring look are simply followed. An unclear result may need a repeat biopsy or molecular testing. A biopsy can be recommended at a suitable center.

Treatment and follow-up

The choice depends on the result of the evaluation:

• Benign nodule: most are simply followed with periodic ultrasound, usually 6–12 months after the first finding and then every 6 months to a year, or sooner when the doctor considers it reasonable; when the nodule is stable the intervals may be lengthened by the doctor. Benign nodules are not routinely treated with thyroid hormone to shrink them.
• A nodule that grows, presses on surrounding structures or causes cosmetic concern: treated with surgery (removal of part or all of the thyroid), or other methods chosen by the team according to the case.
• A nodule that makes excess hormone (hyperthyroidism): treated with medicines, radioactive iodine or surgery.
• A fluid cyst that returns: may be drained or treated with specific procedures.
• Cancer or strong suspicion: treated mainly with surgery, sometimes followed by radioactive iodine therapy and thyroid hormone. Most thyroid cancers have a very good outlook.

After removal of the thyroid (or most of it), lifelong levothyroxine is usually needed, as explained on the page about hypothyroidism.

When to see a doctor

• when you feel or see a swelling in the neck;
• when an ultrasound has found a nodule that should be assessed by an endocrinologist;
• hoarseness or difficulty swallowing that does not pass within a few weeks;
• a nodule that grows quickly or becomes hard;
• a fast heartbeat, tremor and unexplained weight loss.

Bring the reports of earlier ultrasounds and your latest tests, because comparison with earlier findings is very valuable. This information is educational and does not replace a medical visit.