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.

Keywords: CEUS; MPUS; US-elastography; thyroid nodule; ultrasound.

Figure 1

(a). At B-mode Ultrasound (US), the lesion appeared round-shaped, hypoechoic with irregular margins (EU-TIRADS 5). (b). At color–Doppler US evaluation, the lesion showed no internal or peripheral vascularization (pattern I). (c). At US-Elastography (USE) evaluation, the lesion appeared stiff (ECI: 4.03). (d). At S-Detect evaluation, the lesion suggested intermediate suspicion of malignancy (TIRADS 4). Finally at histology it was identified as a papillary carcinoma.

Figure 1

(a). At B-mode Ultrasound (US), the lesion appeared round-shaped, hypoechoic with irregular margins (EU-TIRADS 5). (b). At color–Doppler US evaluation, the lesion showed no internal or peripheral vascularization (pattern I). (c). At US-Elastography (USE) evaluation, the lesion appeared stiff (ECI: 4.03). (d). At S-Detect evaluation, the lesion suggested intermediate suspicion of malignancy (TIRADS 4). Finally at histology it was identified as a papillary carcinoma.

Figure 2

(a). At B-mode Ultrasound (US), an oval-shaped nodule with mixed ecostructure, some internal fluid areas and smooth margins, was identified (EU-TIRADS 3). (b). At color–Doppler US evaluation, the lesion appeared with internal and peripheral vascularization (pattern III). (c). At Strain Ratio Elastography (SRE) evaluation, the lesion appeared soft (SR 1.13). (d). At Shear Wave Elastography (SWE) evaluation, the lesion appeared soft (2.24 m/s). (e). At CEUS evaluation, the lesion appeared solid and richly vascularized, similar to the surrounding thyroid parenchyma without wash-out. At histology, the lesion was confirmed to be a follicular hyperplasia.

Figure 2

(a). At B-mode Ultrasound (US), an oval-shaped nodule with mixed ecostructure, some internal fluid areas and smooth margins, was identified (EU-TIRADS 3). (b). At color–Doppler US evaluation, the lesion appeared with internal and peripheral vascularization (pattern III). (c). At Strain Ratio Elastography (SRE) evaluation, the lesion appeared soft (SR 1.13). (d). At Shear Wave Elastography (SWE) evaluation, the lesion appeared soft (2.24 m/s). (e). At CEUS evaluation, the lesion appeared solid and richly vascularized, similar to the surrounding thyroid parenchyma without wash-out. At histology, the lesion was confirmed to be a follicular hyperplasia.

Figure 2

(a). At B-mode Ultrasound (US), an oval-shaped nodule with mixed ecostructure, some internal fluid areas and smooth margins, was identified (EU-TIRADS 3). (b). At color–Doppler US evaluation, the lesion appeared with internal and peripheral vascularization (pattern III). (c). At Strain Ratio Elastography (SRE) evaluation, the lesion appeared soft (SR 1.13). (d). At Shear Wave Elastography (SWE) evaluation, the lesion appeared soft (2.24 m/s). (e). At CEUS evaluation, the lesion appeared solid and richly vascularized, similar to the surrounding thyroid parenchyma without wash-out. At histology, the lesion was confirmed to be a follicular hyperplasia.