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Thyroid nodules are solid or fluid lumps (cysts) that form on the butterfly-shaped thyroid gland, located at the front of the neck.
Multiple nodules found within the same thyroid gland have a different medical term – multinodular goitre.
Thyroid nodules may not give rise to symptoms, which is why many of them are found incidentally during medical consultations, routine check-ups or investigations (e.g., ultrasounds, CT scans or PET scans) for other health problems.
Most nodules are either simple “overgrowths” of normal thyroid tissue, fluid-containing cysts or slowly growing benign tumours called adenomas. A small percentage of these nodules can be cancerous. The risk of thyroid cancer is higher if you had a history of radiation to the head and neck for other medical conditions, or if you have a family history of thyroid cancer.
While the detection of these lumps are not urgent causes for concern, it is still crucial for patients to observe and note any changes in the lumps' properties, shape and size, as rapid growth in a nodule could suggest cancer.
Image showing position of thyroid gland in neck among other organs
Most thyroid nodules do not cause symptoms. Thus, most people may only realize they have a thyroid nodule when it is large enough to be noticed in the mirror, or found by chance during a physical examination, or incidentally picked up on investigations like ultrasounds, CT scans or PET scans.
Some symptoms may include:
While symptoms of thyroid nodules are gradual and may not be very obvious, complications such as bleeding into the thyroid cyst or nodule may cause a sudden and painful swelling in the neck. Patients who have advanced thyroid cancer may also have a hoarse voice and difficulty swallowing.
If you have a lump in the middle of your neck (below your Adam’s apple) or just off the centre, which moves with swallowing, it is probably a thyroid nodule. Your doctor will be able to confirm this finding. The lump you feel may be either a solitary nodule or a dominant nodule in a background of multiple nodules, or even a diffusely enlarged thyroid gland.
In Singapore where iodine deficiency is not a problem, there are no preventable causes of thyroid nodules or goitre. Radiation is a risk factor for thyroid cancer, but this is a rare occupational or treatment risk for a small group of individuals.
The exact cause of thyroid nodules is not known, but the following factors may be involved:
The most common cause of multinodular goitres is iodine deficiency. However, it may still develop in some individuals who have enough iodine. In these people, the cause is not well understood.
Regardless of how a thyroid nodule is detected, an ultrasound scan of the thyroid gland is the ideal scan to characterise thyroid nodules. The appearance of each thyroid nodule in the ultrasound scan will guide us as to how likely a nodule is to be benign or cancerous. However, it is still not possible to differentiate between benign or cancerous thyroid nodules just by using an ultrasound scan alone. A fine needle aspiration and biopsy (FNAB) may be recommended if the nodule has ultrasound features suspicious of cancer.
Fine needle aspiration biopsy (FNAB) is a minor procedure performed in the clinic or as a day surgery procedure, where a fine needle is inserted into the nodule under ultrasound guidance to obtain cells for further analysis in the laboratory to determine if the nodule is cancerous or non-cancerous.
Thyroid function tests assess the levels of your thyroid hormones (T4) and thyroid-stimulating hormone (TSH). These tests evaluate the health of your thyroid gland before any further tests are done.
If you have hyperthyroidism and your levels of thyroid hormones are too high, you may experience symptoms such as palpitations, feeling hot easily, irritability, diarrhoea, weight loss, and increased appetite.
On the other hand, if you have hypothyroidism, meaning your thyroid gland is underactive, you may feel tired and lethargic, gain weight easily, experience constipation, have memory loss, and feel cold easily.
In addition to FNAB and thyroid function tests, other diagnostic tests may be performed to further evaluate thyroid nodules, such as a thyroid uptake scan.
Thyroid uptake scan
The purpose of this scan is to determine if the thyroid nodule is producing too much thyroid hormones in a patient who has thyroid nodules and hyperthyroidism. It involves an injection of a small amount of radioisotope (known as tracer) to distinguish between functioning and nonfunctioning nodules.
A nodule that takes up more of the tracer than normal thyroid tissue is known as a “hot” nodule, whereas a nodule that takes up less tracer than normal thyroid tissue is known as a “cold nodule”. “Hot” nodules are rarely cancerous. It is not possible to differentiate between a “cold” nodule which is cancerous and one that is not cancerous. This will depend on the presence of suspicious imaging features of thyroid ultrasound which is usually performed together with the thyroid uptake scan and potential further evaluation by FNAB.
Most patients with benign thyroid nodules do not require any specific treatment and are usually followed up with ultrasound. If cancer is suspected, surgery would be recommended.
The treatment for thyroid nodules depends on the nature of the nodule, whether it is benign or malignant, and if it causes symptoms.
Cancer: Surgery is the treatment of choice. Depending on the size of the tumour, either half or the entire thyroid gland may need to be removed. Additional treatment with radioiodine may be necessary.
Benign nodules: Benign nodules may be observed if not causing any symptoms. Follow-up of the nodules is usually by ultrasound, and the interval will be decided by your doctor.
Surgery is an option if symptoms are present, including difficulty swallowing or breathing, or even just to remove the unsightly lump
Radiofrequency ablation (RFA): RFA treats benign thyroid nodules by delivering thermal energy to the targeted nodule, causing coagulative necrosis and shrinkage of the nodule. This minimally invasive procedure offers a low-risk alternative to surgery, providing symptomatic relief and cosmetic improvement for patients with benign thyroid nodules.
Indeterminate nodules: If the nature of the nodule is indeterminate on FNAB, your doctor will discuss with you the options of repeating the FNAB, close observation or surgery. The risk of your nodule being cancerous depends on the exact findings on ultrasound and FNAB
Thyroid surgery is performed under general anaesthesia and may be:
Hemithyroidectomy: Removal of half the thyroid gland, for benign nodules or small cancers.
Your surgeon will explain which operation you require and the reason for it.
In suitable patients, thyroid surgery can be performed without using a neck incision. The surgery may be endoscopic or robot-assisted, with skin incisions located in the axilla or armpit and less visible than a neck scar.
Some thyroid cancers can spread to the lymph nodes in the neck, and your doctor may need to remove some of the lymph nodes in your neck during the operation as well.
Immediately post-surgery, there may be a drain placed in the neck to drain residual fluid and prevent a collection. If you are otherwise well and not requiring any other care, you may be discharged home with the drain in your neck after being taught how to care for it. You will then be given a follow up appointment in clinic to remove this drain.
In terms of long-term follow up, regular outpatient appointments for further blood tests and scans may be scheduled to check on thyroid hormone/calcium levels and in case the cancer recurs. These tests are crucial for timely treatments if the cancer recurs, or complications arise.
