Introduction: Thyroid nodular goitre is one of the most common endocrine disorders. Differentiating between benign and malignant lesions is an emerging challenge in endocrinological practice. Ultrasonography (US) remains the most commonly applied method in the preliminary assessment of lesions and is the basis for the decision as to fine needle aspiration biopsy (FNAB) and further diagnostics. Many studies have evaluated the diagnostic value of US malignancy features. However, they focused mainly on papillary thyroid cancer (PTC). It remains unclear whether other types of thyroid carcinoma (TC) are also characterised by the same US features. The aim of this study was to assess the usefulness of US features considered as markers in the diagnosis of medullary thyroid cancer (MTC).
Material and methods: The PubMed/MEDLINE and Cochrane Library databases were searched to identify studies on US features of MTCs. The random-effects model was used to calculate pooled sensitivity and specificity and odds ratios (OR) - if a comparison with PTCs was available.
Results: Hypoechogenicity was present in 83.4% of MTCs, and 32.7% were markedly hypoechogenic. None of the 157 MTCs was hyperechogenic. Sensitivity of halo absence was 88.9%, but irregular margins were present in 38.0%. 35.5% of MTCs had microcalcifications, and 27.0% had macrocalcifications. 14.4% presented 'taller than wide feature' (higher anteroposterior than transverse diameter). Apart from macrocalcifications, all these features occurred insignificantly less often in MTCs than in PTCs.
Conclusions: US features commonly considered as markers of malignancy can be useful also in the diagnostics of MTCs. However, MTCs tend to possess suspicious US features slightly less often than PTCs. Some features, such as hyperechogenicity, can be considered to be strong markers of benign status. Although the US appearance of the thyroid lesion is an important diagnostic factor, it is worth remembering that it does not allow for a definitive differentiation between benign and malignant nodules. In the case of MTCs, as well as other TCs, US examination remains a valuable diagnostic tool, but should always be interpreted carefully in the context of other examinations.