Thyroid Nodule Facts

 What is the thyroid gland?

Thyroid gland is located in the neck. It is an endocrine organ that regulates metabolism by secreting thyroid hormones. It regulates our body's use of energy, keeps us warm, and helps the brain, heart, muscles, and other organs function normally.

What are the signs and symptoms of a thyroid nodule?

Thyroid nodule means that thyroid cells grow and form a mass in the thyroid gland. The growth of the thyroid gland with or without nodules is called goitre. If there is a single nodule, it is diagnosed as nodular goitre, and if there are many nodules, it is diagnosed as multinodular goitre. Sixty percent of adults have thyroid nodules. Thyroid nodules are 3 times more common in women than in men. Most nodules do not cause symptoms. They can rarely cause pain, and when they enlarge and compress on the oesophagus, they can cause difficulty swallowing, when they compress on the trachea, they can cause shortness of breath, when they compress on the vocal cord nerves, they can cause hoarseness, they can cause a palpable lymph node in the neck, and can cause symptoms such as palpitations and sweating in the presence of hyperthyroidism (toxic goitre).

• Multinodular goitre causing compression symptoms 
• Patients with nodular goitres. 
• Thyroid nodule in the left lobe. 

What is the cause of thyroid nodule?

Ninety percent of thyroid nodules are benign (Colloidal and cystic nodules, thyroiditis and follicular adenomas).

Nodules that have gained autonomy are self-activated, can produce excess thyroid hormone and sometimes cause hyperthyroidism. The exact cause of the growth of non-cancerous (benign) nodules is not known. Thyroid cancer is the most important cause of thyroid nodule. Thyroid cancer (malignancy) is present in 5-15% of thyroid nodules.

How is thyroid nodule diagnosed?

Diagnosis is often made through history, physical examination, thyroid or neck ultrasound, fine needle aspiration biopsy and diagnostic thyroidectomy. If possible and necessary, molecular testing is performed, and if there is toxic nodular goitre/hyperthyroidism, thyroid scintigraphy is performed. In the history; thyroid cancer in the family, whether there has been exposure to radioactive iodine, whether there has been a thyroid surgery before and the symptoms and complaints mentioned above are asked.

What is a thyroid ultrasound?

Thyroid ultrasound is used to evaluate thyroid nodules by providing visualization of thyroid tissue by reflection of sound waves. Neck ultrasound is performed when neck lymph nodes need to be evaluated. Ultrasound evaluates whether the nodule is solid or cystic (containing fluid), and whether it has features that accompany thyroid cancer (microcalcification, hypoechogenicity, irregular border, increased anterior-posterior diameter). It can also be monitored whether the nodules are growing. Ultrasound is also used when performing a fine needle aspiration biopsy of the thyroid.

Which thyroid nodules should undergo fine needle aspiration biopsy (FNAB)?

Nodules are classified as low, medium and high-risk nodules according to ultrasound findings and size. FNAB is considered the gold standard for most medium and all high-risk nodules. FNAB is recommended for very low risk nodules that are 2 cm and larger, for low-risk nodules that are 1.5 cm and larger, and for medium and high-risk nodules that are 1 cm and larger. In general, FNAB is a practical approach for solid nodules that are 1 cm and larger and have at least 1 more factor for thyroid cancer among the following findings in thyroid ultrasound such as microcalcification, hypoechogenicity, irregular border, increased anterior-posterior diameter (moderate or high-risk nodule). FNAB could also be performed for nodules between 0.5-1 cm and have one risk factor.

What is a fine needle aspiration biopsy (FNAB)?

It is an outpatient test. It has almost no side effects. Cells are obtained from the thyroid nodule with a fine needle and examined by a pathologist under a microscope. In 60% of those who have undergone FNAB, the result is benign (Bethesda category II, benign cells). Definite thyroid cancer (Bethesda category VI) is found in 5% of patients, while malignancy is suspected in 20-30% (Bethesda categories III, IV, V). Non-diagnostic/insufficient results are obtained in 5-10% (Bethesda category I).

What is molecular testing?

Molecular analysis of FNAB could be applied in cases of AUS (Bethesda III), Follicular neoplasia (Bethesda IV) or suspicion of malignancy (Bethesda V). Follow-up or surgery can be applied in Bethesda III, IV nodules according to the molecular test result.

When is thyroid scintigraphy performed? 

If there is a nodule in patients with hyperthyroidism (excessive thyroid function, toxic goitre), thyroid scintigraphy could be performed with low-dose radioactive iodine to understand whether hyperthyroidism is related to this nodule.

Treatment

Surgery is applied to thyroid cancer or nodules suspected of cancer. In some small (less than 1 cm) thyroid cancers, follow-up can be done without surgery. If the FNAB result is benign, periodic annual examination and follow-up with ultrasound is recommended. If the nodule is not growing and no unfavourable factors are revealed on ultrasound, follow-up is continued. Otherwise, a new FNAB is performed and the patient is re-evaluated. If there is malignancy, suspicion of malignancy or follicular neoplasia, surgery is recommended, whereas if there is non-diagnostic or atypia of undetermined significance (AUS) FNAB is repeated after 3 months. If the result does not change, surgery or follow-up is recommended considering the characteristics of the nodule (history, physical examination, size of the nodule, whether the nodule is single or multiple, whether it is unilateral or not, risk factors on ultrasound). In surgery, especially in Bethesda III (AUS), Bethesda IV (Follicular neoplasia) and Bethesda V (Suspicion of malignancy) nodules, lobectomy + isthmectomy (removal of the unilateral thyroid lobe together with the isthmus) or total or near-total thyroidectomy is recommended, taking into account the characteristics of the nodule. Even if the nodules are benign, surgery is still recommended if there are signs of compression symptoms or findings of hyperthyroidism.

Prof. Dr. Bekir Kuru

General Surgery