Thyroid Nodules: Diagnostic evaluation and Management Options

A thyroid nodule is a lump within the thyroid gland that is radiologically distinct from the surrounding thyroid tissue (picture1). Thyroid nodules are common and are usually benign, but some require further assessment to rule out thyroid cancer or hormone overactivity. Diagnosis typically involves an ultrasound, thyroid blood tests, and sometimes a fine needle biopsy, with treatment depending on whether the nodule is benign, suspicious, overactive, or causing symptoms. As an experienced thyroid surgeon in Melbourne, I provide comprehensive thyroid nodule assessment, including surgeon-performed ultrasound and ultrasound-guided biopsy, to ensure an accurate diagnosis and discuss all appropriate treatment options. These may include active surveillance, minimally invasive treatments such as radiofrequency ablation (RFA), or thyroid surgery when required.

Table of Contents

How are thyroid nodules assessed?

Picture 1. Arrow pointing to a solid thyroid nodule on an ultrasound image.

As with other endocrine glands, when assessing a thyroid nodule, both structure and function of the nodule should be evaluated. Structurally the nodules may be divided into cystic (fluid-filled), solid, or mixed solid/cystic. Ultrasound (US) scan is used to assess the structure of thyroid nodules. While most cystic nodules are benign, solid nodules may need further evaluation with biopsy to determine their malignant (cancerous) potential.

The function of thyroid nodules is often assessed with blood tests and nuclear medicine (NM) thyroid scan. Based on their appearance on the NM scan, thyroid nodules may be divided into cold (underactive), hot (overactive), or warm (similar function to the surrounding thyroid tissue).  

Therefore, a thyroid US scan and a blood test for thyroid function are the minimum tests required when assessing patients with thyroid nodule(s). If the blood test shows hyperactive thyroid, a NM thyroid scan is also done to determine the cause of overactivity.  

When thyroid nodules are assessed with US scan the so-called TI-RAD classification (Thyroid Imaging – Reporting & Date System) is used to determine their malignant potential and the need for follow up or biopsy. Each nodule is given a score of 1 to 5 based on its US features with increasing chance of malignancy with higher scores (Table 1).

TI-RADS score	Chance of malignancy	Recommendation
1 Benign	<2%	No biopsy
2 Not suspicious	<2%	No biopsy
3 Mildly suspicious	5%	Biopsy if ≥ 2.5 cm Follow-up if ≥ 1.5 cm
4 Moderately suspicious	5–20%	Biopsy if ≥ 1.5 cm Follow-up if ≥ 1 cm
5 Highly suspicious	>20%	Biopsy if ≥ 1 cm Follow-up if ≥ 0.5 cm

Table 1. TI-RAD classification of thyroid nodules based on their ultrasound features.

How is thyroid biopsy done?

Picture 2. Thyroid biopsy is done with a thin need through the skin under ultrasound guidance.

Thyroid biopsy is done via “fine needle aspiration” (FNA) under US guidance. A very thin needle (smaller than the needle used to draw blood) is passed through the skin into the nodule under US guidance (Picture 2). The thyroid cells that become trapped inside the needle are spread on glass slides and sent to pathology for analysis under a microscope. Your doctor will receive the results often within 5 days.

What are possible results of thyroid nodule biopsy?

Pathologic analysis of thyroid FNA biopsy will result in one of the following 6 results:

1. Non-diagnostic: Simply enough cells were not obtained to arrive to a diagnosis. The chance of malignancy is 1-4%. A repeat FNA biopsy is recommended in about 3 months.

2. Benign: This is reassuring. US follow up may be recommended based on US findings.

3. Indeterminate: Risk of malignancy is 5-15%. Repeat FNA biopsy is recommended in about 3 months.

4. Follicular neoplasia: The only way to know if a follicular neoplasia is benign or malignant is to remove the entire nodule through a hemithyroidectomy (removal of the right or left half of thyroid containing the nodule) and send it for pathological assessment. The risk of malignancy in these nodules is 15-30%.

5. Suspicious for malignancy: The risk of malignancy is about 60-75%. At least a diagnostic hemithyroidectomy is required to confirm or rule out malignancy.

6. Malignant: Definitive treatment will be required. Your surgeon will discuss this with you which may include hemi- or total thyroidectomy with or without removal of neck lymph nodes.

What are the treatment options for hot nodules?

Picture 3. Arrow pointing to a solitary hot nodule in the right thyroid lobe on a nuclear medicine thyroid scan.

As mentioned above, thorough assessment of a thyroid nodule includes assessment of its structure using US as well assessment of its function. If the thyroid function test indicates thyrotoxicosis (hyperactive thyroid), a NM scan is done to identify the cause. In about 5% of the cases thyrotoxicosis is due to a solitary hot nodule (Picture 3).

The treatment options in such cases include:

1. Antithyroid medications indefinitely (least favourable)

2. Radioactive iodine: gives good results with a low dose and can also be repeated if necessary. It generally takes about 3-5 months to normalise thyroid function.

3. Surgery in the form of hemithyroidectomy controls thyrotoxicosis more quickly. It is the only viable option if there is suspicion for malignancy, or the nodule itself is symptomatic (cosmetic, or pressure symptoms).

Frequently Asked Questions

• Are thyroid nodules cancer?

  No. Around 90–95% of thyroid nodules are benign (non-cancerous). Only a small proportion represent thyroid cancer. Ultrasound features, together with fine needle aspiration (FNA) biopsy when indicated, allow doctors to accurately assess the risk of malignancy and determine whether surgery is necessary.

• What causes thyroid nodules?

  The exact cause is often unknown. Thyroid nodules may develop as part of the normal ageing process, from benign overgrowth of thyroid tissue, thyroid cysts, inflammation, iodine deficiency, or, less commonly, thyroid cancer. Most nodules are not related to lifestyle or anything you have done.

• Do all thyroid nodules need a biopsy?

  No. Whether a biopsy is recommended depends on both the size of the nodule and its ultrasound appearance using the TI-RADS classification. Many small nodules with reassuring ultrasound features can be safely monitored with periodic ultrasound rather than undergoing biopsy.

• How accurate is a thyroid biopsy?

  Ultrasound-guided fine needle aspiration (FNA) is highly accurate and is the standard test for assessing thyroid nodules. While no test is perfect, FNA reliably distinguishes benign from malignant nodules in most cases. Occasionally, the result is indeterminate, and further testing, repeat biopsy, or surgery may be recommended.

• Can a benign thyroid nodule become cancerous?

  A benign thyroid nodule does not usually transform into cancer. However, because thyroid nodules can occasionally change over time, your doctor may recommend periodic ultrasound surveillance to monitor for significant growth or changes in appearance.

• How often should thyroid nodules be monitored?

  This depends on the size, ultrasound features, and biopsy results. Some benign nodules require no further follow-up, while others are monitored with repeat ultrasound every 12–24 months. Your doctor will recommend an individualised surveillance plan based on your level of risk.

• Can thyroid nodules disappear on their own?

  Some cystic (fluid-filled) thyroid nodules may shrink or even disappear over time. Solid nodules are less likely to resolve spontaneously but often remain stable for many years without causing any problems.

• When should a thyroid nodule be removed?

  Surgery may be recommended if the nodule is cancerous or suspicious for cancer, causes pressure symptoms such as difficulty swallowing or breathing, produces excess thyroid hormone (a hot nodule), continues to grow significantly, or is cosmetically concerning. The decision is based on a combination of ultrasound findings, biopsy results, symptoms, and patient preference.

• Can benign thyroid nodules be treated without surgery?

  Yes. Not all benign thyroid nodules require surgery. Depending on the type of nodule, treatment options may include observation, aspiration of cystic nodules, or minimally invasive procedures such as radiofrequency ablation (RFA), which can significantly reduce the size of symptomatic benign nodules while preserving normal thyroid tissue.

• What is radiofrequency ablation (RFA) for thyroid nodules?

  Radiofrequency ablation (RFA) is a minimally invasive treatment that uses heat to shrink selected benign thyroid nodules without removing the thyroid gland. It is performed under ultrasound guidance through a small needle and usually avoids a neck scar, general anaesthesia, and lifelong thyroid hormone replacement.

• Will I need to take thyroid tablets after thyroid surgery?

  Not always. If only one half of the thyroid gland is removed (hemithyroidectomy), many patients continue to produce enough thyroid hormone and do not require medication. However, if the entire thyroid gland is removed (total thyroidectomy), lifelong thyroid hormone replacement is necessary.

• Can an experienced thyroid surgeon perform the ultrasound and biopsy during the consultation?

  Yes. Surgeon-performed high-resolution ultrasound allows immediate assessment of the thyroid nodule and surrounding lymph nodes during your consultation. When appropriate, an ultrasound-guided biopsy can often be performed at the same visit, reducing delays and helping develop a personalised treatment plan more efficiently.