Thyroid Nodule Characterization: How to Assess the Malignancy Risk. Update of the Literature

Abstract

Ultrasound (US) is the first imaging modality for thyroid parenchyma evaluation. In the last decades, the role of ultrasound has been improved with the introduction of new US software, such as contrast-enhanced ultrasound (CEUS) and US-elastography (USE). USE is nowadays recognized as an essential part of the multiparametric ultrasound (MPUS) examination, in particular for the indeterminate thyroid nodule with possible fine-needle aspiration cytology (FNAC) number reduction; even if further and larger studies are needed to validate it. More controversial is the role of CEUS in thyroid evaluation, due to its high variability in sensitivity and specificity. Semi-automatic US systems based on the computer-aided diagnosis (CAD) system are producing interesting results, especially as an aid to less experienced operators. New knowledge on the molecular mechanisms involved in thyroid cancer is allowing practitioners to identify new genomic thyroid markers that could reduce the number of “diagnostic” thyroidectomies. We have therefore drawn up an updated representation of the current evidence in the literature for thyroid nodule multiparametric ultrasound (MPUS) evaluation with particular regard to USE, the US CAD system and CEUS.

Papillary Thyroid Cancer Prognosis: An Evolving Field

“…Hence, ruling out malignancy by means of ultrasonography (US) and fine-needle aspiration cytology (FNAC) is the main task in their clinical management [ 26 , 27 , 28 ]. After the initial assessment of the presence of TC risk factors, US represents the first imaging technique in thyroid nodule evaluation, in that it detects a number of nodule characteristics known to be associated with malignant lesions [ 29 ]. These include internal structure of the nodule (solid, mixed, or cystic), echogenicity (hyper-, iso-, hypoechoic or markedly hypoechoic), nodule margins (regular, microlobulated, irregular), presence of calcifications (micro- or macrocalcifications), and shape (taller-than-wide or wider-than-tall) [ 29 ].…”

“…After the initial assessment of the presence of TC risk factors, US represents the first imaging technique in thyroid nodule evaluation, in that it detects a number of nodule characteristics known to be associated with malignant lesions [ 29 ]. These include internal structure of the nodule (solid, mixed, or cystic), echogenicity (hyper-, iso-, hypoechoic or markedly hypoechoic), nodule margins (regular, microlobulated, irregular), presence of calcifications (micro- or macrocalcifications), and shape (taller-than-wide or wider-than-tall) [ 29 ]. The US parameters are included in the Thyroid Imaging Reporting and Data System (TI-RADS) score, which shows, compared to the single ultrasound features, greater accuracy in identifying suspicious nodules to be further evaluated by fine needle aspiration cytology (FNAC).…”

“…To date, FNAC remains the gold standard technique in the evaluation of both palpable and non-palpable thyroid nodules [ 25 , 26 , 27 , 28 ]. However, in recent years US evaluation of thyroid nodules has been greatly improved with the introduction of new US software, such as the contrast-enhanced ultrasound (CEUS) and US-elastography (USE) [ 29 ]. In particular, USE has emerged as a valuable tool to discriminate malignant from benign nodules, with diagnostic accuracy greater than TI-RADS, and it should become an additional tool for evaluating thyroid nodule differentiation in combination with conventional US and FNAC, as indicated by the World Federation for Ultrasound in Medicine and Biology (WFUMB) and the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) [ 29 , 30 , 31 , 32 ].…”

“…However, in recent years US evaluation of thyroid nodules has been greatly improved with the introduction of new US software, such as the contrast-enhanced ultrasound (CEUS) and US-elastography (USE) [ 29 ]. In particular, USE has emerged as a valuable tool to discriminate malignant from benign nodules, with diagnostic accuracy greater than TI-RADS, and it should become an additional tool for evaluating thyroid nodule differentiation in combination with conventional US and FNAC, as indicated by the World Federation for Ultrasound in Medicine and Biology (WFUMB) and the European Federation of Societies for Ultrasound in Medicine and Biology (EFSUMB) [ 29 , 30 , 31 , 32 ]. Moreover, new elastic imaging technologies, such as the shear-wave elastography and the strain ratio elastography, seem to be more efficient in characterizing thyroid nodules reported as indeterminate in FNAC, and their use is expected to increase in the coming years [ 33 ].…”

Novel Inhibitor-Based Therapies for Thyroid Cancer—An Update

“…The frequency of diagnosed nodules in palpation is 2–6%, while USG can detect thyroid nodules even in 19–68% of randomly selected individuals [ 89 , 90 ]. Thyroid nodules are found in 8–65% of autopsy specimens [ 91 ]. Among the nodules detected by palpation or USG, approximately 5–15% are malignant [ 92 , 93 ].…”