A thyroid nodule is simply a lump in the thyroid gland. It may be big or small. There may be one nodule or several nodules.

Thyroid nodules are very common, and more common in women with some estimates of palpable thyroid nodes occurring in 6% of the female population and 1.5% of the male population.

Ultrasound detects thyroid nodules in 19-67% of the population. Most thyroid nodules develop from an overgrowth of normal thyroid tissue and are not dangerous. However, around 5% percent of thyroid nodules are cancerous.

Generally, the larger the thyroid nodule the more likely it is to cause compressive symptoms such as a pressure feeling, tightness or a lump in the neck. Thyroid nodules frequently cause no symptoms. Some people simply do not like the appearance of a thyroid nodule. Nodules less than 2cm in size seldom cause symptoms.

If a nodule gets very large it may cause compression of the trachea resulting in shortness of breath on exertion and when lying down. Large thyroid nodules may also cause superior vena cava syndrome with restriction of venous drainage from the head and neck. This is most noticeable when the arms are raised in such activities as hanging out the washing. Patients may go red in the face when doing such activities (positive Pemberton’s sign).

Thyroid Nodules and Blood Tests

Most patients with thyroid nodules have a normal thyroid blood test. Most patients with thyroid nodules are not hypothyroid (underactive thyroid) or hyperthyroid (overactive thyroid). All patients with thyroid nodules should have a blood test to check that the thyroid hormone levels are normal.

Occasionally patients with a thyroid nodule have a high thyroid hormone level and this will need to be treated with medication. (See hyperthyroidism).

Thyroid Nodules and Ultrasound

An ultrasound scan of the thyroid will determine if the thyroid is enlarged and provide details of any nodules present. Thyroid nodules are assessed with a thyroid ultrasound and are graded using the tirads grading system from 1-5. A tirads 1or 2 nodule is benign, while a tirads 5 nodule is highly suspicious for cancer. Tirads 3, 4 and 5 are mildly, moderately and highly suspicious respectively for malignancy (cancer).

(See Thyroid Ultrasound section).

Thyroid Nodules and Ultrasound Guided FNA

An ultrasound guided FNA (fine needle aspiration) needle biopsy helps to determine which thyroid nodules are likely to be cancerous. Under local anaesthetic, and ultrasound guidance, a fine needle is guided into the thyroid nodule and a small sample is taken. Ultrasound guided FNA may be required depending on the size and thyroid ultrasound characteristics (tirads grade) of the thyroid nodule. 

The following thyroid nodules need ultrasound guided FNA:

• Tirads 3 nodules greater than or equal to 25mm
• Tirads 4 nodules greater than or equal to 15mm
• Tirads  5 nodules greater than or equal to 10mm 

FNA results are reported as:

• Bethesda 1: non diagnostic
• Bethesda 2: benign (not cancerous)
• Bethesda 3: atypia of uncertain significance (AUS)
• Bethesda 4: follicular neoplasm
• Bethesda 5. suspicious for malignancy
• Bethesda 6. malignant (cancer).

Thyroid nodules that are Bethesda 3, 4 and 5 on FNA are mildly, moderately and highly suspicious for malignancy respectively.

Abnormal lymph nodes noted on the ultrasound scan also require an ultrasound guided FNA.

(See Ultrasound Guided FNA section).

Thyroid Nodules and Molecular Testing

Molecular testing of thyroid nodules also helps to determine which thyroid nodules are likely to be cancerous. It gives additional information to FNA. It is most suitable for thyroid nodules that are Bethesda 3 and 4 on FNA, especially if those nodules are also tirads 3 and 4.

Molecular testing determines the likelihood of cancer, categorising patients into low, intermediate and high risk of cancer. Molecular testing is performed similarly to ultrasound guided FNA by taking a small sample from the thyroid nodule with a needle under ultrasound guidance. (See molecular testing section.)

If your thyroid nodule is not cancerous and is not causing symptoms, then no treatment is required. If your thyroid nodule is not cancerous and is causing symptoms either surgery or radiofrequency ablation of the nodule are good options. (See radiofrequency ablation of thyroid nodules section.)