Thyroid ultrasound examination allows detailed and accurate description of
thyroid nodule features including nodule size, location, echotexture, echogenicity,
margins, shape, presence and extent of cystic content, calcifications, and nodular flow
pattern on Doppler study. The finding of a colloid signal, complete thin peripheral halo,
or complete rim calcification makes thyroid nodule malignancy less likely, whereas
nodule hypoechogenicity, microcalcifications, irregular margins, taller than wide
shape, and interrupted rim calcification with extrusion of soft tissue are suggestive of
malignancy. In contrast to papillary thyroid carcinoma, follicular thyroid carcinoma
does not display microcalcifications or cystic content on ultrasound, often has a regular
margin and may feature a peripheral halo. The role of ultrasound elastography and
Doppler flow in distinguishing benign from malignant nodules remains to be
determined. Importantly, no single ultrasound feature in isolation is predictive of
nodule malignancy or benignancy, and the risk of malignancy is best characterised
using a combination of ultrasound features. Two widely used thyroid malignancy risk
stratification systems are the American Thyroid Association and the European Thyroid
Imaging Reporting and Data System. These classification systems improve the
sensitivity of ultrasound for the detection of thyroid malignancy without compromising
its specificity and allow the recommendation of nodule size cut-offs for FNA biopsy.
Keywords: Anaplastic thyroid carcinoma, Colloid, Differentiated thyroid cancer,
European Thyroid Imaging Reporting and Data System, Follicular thyroid
carcinoma, Hypoechoic, Thyroid, Nodule, Ultrasound, Multinodular goitre,
Retrosternal goitre, Papillary thyroid carcinoma, Medullary thyroid carcinoma,
Microcalcifications, Rim calcification, Taller-than-wide, Spongiform, Peripheral
halo.
