​Thyroid nodules are usually incidentally picked up during health screenings in the primary care setting. General practitioners are therefore key to initiating investigations to identify potential malignancies. Find out more about the latest in assessment and treatment options, and when specialist referral is needed.

INTRODUCTION TO THYROID NODULES

The occurrence of thyroid nodules is very common, and it has been shown that nodules can be detected with ultrasound (US) in up to 68% of a random population, with increased incidence in females and the elderly¹.

Most of these patients with thyroid nodules are asymptomatic, with the nodules being picked up incidentally on routine head and neck imaging for other conditions, or via US done during health screening in the primary care setting.

Incidence of thyroid cancer

Fortunately, the vast majority of thyroid nodules (> 95%) are benign and do not cause problems in the patients’ lifetimes. Congruent with the increased detection of thyroid nodules, the incidence of thyroid cancer is also increasing globally.

In Singapore, thyroid cancer is the eighth most common cancer amongst females, with an incidence of 10.9 per 100,000 individuals. Of note, amongst younger females less than 50 years of age, it ranks in the top three commonest malignancies.

The priorities in the evaluation of patients with thyroid nodules will therefore be to exclude malignancy and to identify symptomatic patients who may benefit from intervention.

CLINICAL PRESENTATION

Figure 1 shows the symptoms, signs and red flags to look out for in the presentation of thyroid nodules.

Figure 1

TYPES OF INVESTIGATIONS

1. Thyroid function test

When it is needed

A thyroid function test (TFT) should be performed in the initial assessment of a patient with a thyroid nodule or goitre, especially if they have symptoms suggestive of thyroid hormonal dysfunction.

Managing thyroid hormonal dysfunctions

The treatment of hyperthyroidism or hypothyroidism can be initiated in the primary care setting and these patients can continue to follow up with their general practitioners once their thyroid function is controlled.

For patients with thyroid functions that are more difficult to control, or in the presence of red flags or atypical features, referral for specialist evaluation should be considered.

2. Thyroid ultrasound

When it is needed

A US of the thyroid with evaluation of lymph nodes should be performed in all patients presenting with thyroid nodules or goitres.

Objectives

The objectives of ultrasonography are to:

• Confirm the clinical diagnosis
• Evaluate the size of the nodules/goitre objectively (allowing a baseline for surveillance)
• Assess for suspicious features that will necessitate further investigation with a fine needle aspiration cytology

Standardised scoring system

However, US reports, until recently, lacked standardisation and can be difficult to interpret. Tracking nodules across various time points can also be challenging.

Since mid-2022, the reporting of US thyroids in SingHealth has followed a similar format regardless of performing institution. Nodules are labelled the same way on follow-up scans.

In addition, nodules are now reported according to the Thyroid Imaging Reporting & Data System (TI-RADS)² (Figure 2) . TI-RADS is a scoring system which has been validated for reproducibility with clear criteria for nodule sampling, allowing a more streamlined approach. There is also evidence to show that it has reduced sampling rates.


Figure 2

3. Fine needle aspiration cytology

When it is needed

The introduction of TI-RADS in thyroid sonography has provided a standardised and objective tool for thyroid nodule assessment, thereby reducing ambiguity around which nodules require cytologic evaluation.

Suspicious nodules are further investigated with fine needle aspiration cytology (FNAC).

Procedure and reporting

In this procedure, which can be US-guided, a needle is introduced into the nodule to collect cells. This is generally a safe procedure and can be performed as day surgery.

The FNAC results will then be reported by the pathologists using the Bethesda system³ (Figure 3), which estimates a higher risk of malignancy with corresponding higher Bethesda grading. This then provides the attending clinician with a guide for counselling the patient regarding the management options and recommendations.

Figure 3 2017 Bethesda System for Reporting Thyroid Cytopathology

NIFTP: Non-invasive follicular thyroid neoplasm

MANAGEMENT OPTIONS

1. Ultrasound surveillance

As the majority of thyroid nodules are benign and indolent, and do not cause symptoms, they can generally be monitored with US surveillance. These include:

• TR3-5 nodules that may not meet the size criteria for FNAC
• FNAC-proven benign nodules and for which patients are asymptomatic

Follow-up screening recommendations

As the risk of malignancy increases with higher TI-RADS grading, the recommended frequency of performing US thyroid surveillance is as follows:

• TR1-2 nodule: US surveillance is not routinely required, especially for asymptomatic patients. Patients may be advised to observe themselves and return if symptomatic.

• TR3 nodule: Follow-up at 1, 3 and 5 years

• TR4 nodule: Follow-up at 1, 2, 3 and 5 years

• TR5 nodule: Annual follow-up till 5 years

2. Surgery

Thyroidectomy is a common and generally safe head and neck surgical procedure and may be indicated for some patients who present with thyroid nodules or goitres.

The extent of surgery will either be a hemithyroidectomy (lobectomy) or a total thyroidectomy. In addition, for cancer cases, additional surgical procedures may be performed as indicated (e.g., neck dissection for lymph node clearance).

Indications

The indications for surgery are:

• Proven or suspected thyroid malignancy
• Benign nodules/goitres causing compressive symptoms
• Thyrotoxicosis resistant to medical therapy
• Patient preference

Surgical methods

a. Traditional neck incision

The majority of thyroidectomies are performed via the traditional neck (transcervical) incision. This surgical approach is well-established and provides the most direct access to the thyroid gland, thereby allowing safe instrumentation to remove the thyroid gland while preserving vital adjacent structures such as the recurrent laryngeal nerve and the parathyroid glands.

Although this approach invariably requires a neck scar, the majority of cases heal very well and are usually not conspicuous with time.

b. Remote-access procedures

Remote-access approaches (e.g., transaxillary, retroauricular or transoral approaches) avoid an anterior neck scar but surgical access to the thyroid gland is not as direct, requiring a wider extent of dissection and longer operative times.

These approaches may not be suitable for certain patients such as those with larger nodules/goitres or thyroid malignancy. Careful patient selection with thorough counselling is therefore imperative for patients who may be keen on these remote-access procedures.

3. Thyroid nodule ablation

Thyroid ablation, first introduced in Singapore in 2017, has been shown to be effective in treating symptomatic benign thyroid nodules.

This procedure involves introducing a small probe into the nodule, after which heat is generated to ablate (or destroy) the tumour. Size reduction of the nodule then takes place slowly over months.

The most common technology used is that of radiofrequency ablation (RFA). It is minimally invasive, can be performed as day surgery and is shown to be effective in shrinking benign nodules. Selected patients with small papillary thyroid cancers who cannot undergo surgery may also be candidates for thyroid nodule ablation.

REFERENCES

1. 2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer.

2. Tessler FN, et al. ACR Thyroid Imaging, Reporting and Data System (TI-RADS): White Paper of the ACR TI-RADS Committee. Journal of the American College of Radiology. 2017 May;14(5):587–959.

3. Ali SZ, Cibas ES. The Bethesda System for Reporting Thyroid Cytopathology, 2nd ed. Cham, Switzerland: Springer; 2017.

Dr Too Chow Wei graduated from the Faculty of Medicine, National University of Singapore in 2003. He subsequently trained at various hospitals in Singapore in the diagnostic radiology training programme and attained specialisation accreditation in 2012.

He is currently a Senior Consultant at the Department of Vascular and Interventional Radiology and the Director of Interventional Services at Singapore General Hospital. He has a keen interest in the realm of interventional oncology and palliation, with experience in the ablation of liver, lung, kidney and bone tumours.


Dr Tay Ze Yun graduated from the National University of Singapore and received his medical degree from the Yong Loo Lin School of Medicine in 2008. He subsequently joined the SingHealth Otolaryngology Residency Programme as part of the inaugural batch of residents and completed his specialist training in 2016.

In pursuit of his sub-speciality interest in head and neck surgery, he completed the two-year SingHealth Duke-NUS Head & Neck Centre Fellowship Programme (2016-2018). He was subsequently awarded the Ministry of Health’s Health Manpower Development Plan award in 2018 to pursue a surgical fellowship in advanced head and neck surgical oncology at the world-renown Chang Gung Memorial Hospital in Taiwan.

Dr Tay also completed the International Federation of Head and Neck Oncologic Societies fellowship and graduated with honours in 2020. He is currently a Consultant at the Departments of Otorhinolaryngology –Head & Neck Surgery at Sengkang General Hospital and Singapore General Hospital.

GPs can call the SingHealth Duke-NUS Head & Neck Centre for appointments at the following hotlines:

Singapore General Hospital: 6326 6060
Changi General Hospital: 6788 3003
Sengkang General Hospital: 6930 6000
KK Women’s and Children’s Hospital: 6692 2984
National Cancer Centre Singapore: 6436 8288
National Dental Centre Singapore: 6324 8798