Various risk stratification systems exist to categorize the risk of malignancy based on the ultrasound appearance of a thyroid nodule. The EU-TIRADS issued by the European Thyroid association in 2017 was the last to have been published . This system categorizes nodules into five categories ranging from 1 – normal appearances to 5 – malignant on US criteria as illustrated in Table 1 and Figure 1.
|CATEGORY||US FEATURES||MALIGNANCY RISK, %|
|EU-TIRADS 1: normal||No nodules||None|
|EU-TIRADS 2: benign||Pure cyst
|EU-TIRADS 3: low risk||Ovoid, smooth isoechoic/hyperechoic
No features of high suspicion
|EU-TIRADS 4: intermediate risk||Ovoid, smooth, mildly hypoechoic
No features of high suspicion
|EU-TIRADS 5: high risk||At least 1 of the following features of high suspicion:
– Irregular shape
– Irregular margins
– Marked hypoechogenicity (and solid)
The use of colour Doppler and power Doppler imaging for characterisation of thyroid nodule vascularity is widely used currently. It is considered a nonspecific feature for malignancy even if the presence of intranodular flow raises more concerns than if there is no flow or just perinodular flow is seen. A new Doppler technique was recently developed that improved microvascular flow imaging (Figure 2). Its diagnostic capacities to better detect malignancy in thyroid nodules has to be demonstrated in large and unselected population .
The primary application of elastography is the differential diagnosis of thyroid cancer. Nevertheless, despite the increasing data coming from the literature, a univocal consensus on its role in the selection of thyroid nodules to biopsy is still lacking .
Nodules are selected for fine-needle aspiration biopsy on the basis of ultrasound features, size, and high-risk clinical history. Cytology results are classified by the Bethesda system into six categories ranging from benign to malignant. Limitations of FNA include a substantial rate of inconclusive results or indeterminate interpretations (2–30%). When cytology is indeterminate, molecular testing can further risk-stratify patients for observation or surgery. Core-needle biopsy (CNB) has been suggested as a complementary or even alternate method to FNA with a greater diagnostic accuracy compared to repeated FNA but sill with some limitations regarding differentiation between follicullar neoplasms and hyperplastic nodules .
There is an increasing interest to use ultrasound-guided thermal ablation procedures to treat both benign and malignant thyroid nodules. Thermal ablation techniques are differentiated based on the method used to develop this temperature differential and include radiofrequency ablation (RFA), laser ablation, microwave ablation and high-intensity focused ultrasound. For benign thyroid nodules, RFA appears the most effective US-guided ablation technique for treating solid, mixed, and spongiform nonfunctioning thyroid nodules. RFA is a developing application in primary thyroid cancer with some efficacy in the setting of recurrent and residual thyroid malignancy. Standardization of practices and reporting has emerged as an important component of multidisciplinary application of these technologies .
There is evidence that AI increases diagnostic accuracy and significantly limits inter-observer variability by using standardized mathematical algorithms. It could also be of aid in practice settings with limited sub-specialty expertise, offering a second opinion by means of radiomics and computer-assisted diagnosis. However, the real effectiveness of AI systems remains controversial, taking into consideration the largest and most scientifically valid studies .
The author has no competing interests to declare.
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