Vytautas Dūdėnas, Vaida Ruseckaitė, Marius Daniulaitis
Lithuanian university of health sciences, ,faculty of medicine, Kaunas, Lithuania
Introduction: tyhyroid nodules (TN) are a common finding in clinical practice. While most of the nodules are benign, less than 10% prove to be malignant. US is a low-cost, non-invasive, safe imaging examination, which is able to qualitatively analyze the nodule’s features. [1, 2, 4, 10] To this date, there is no US sign which is considered to be pathognomonic of malignancy, however, combining multiple US methods, such as strain elastography (SE), shear-wave elastography (SWE) and ultrasound guided fine-needle aspiration (FNA), helps to determinate the risk of malignancy in a TN. 
Aim: to review scientific literature and emphasize the features of ultrasonographic methods, which are used in the differentiation between benign and malignant thyroid nodules.
Materials and methods: literature analysis. A research of articles in the English language on the “PubMed” 2012 to 2017 database. Keywords used in the search: “thyroid nodule”, “ultrasonography”, “benign”, “malignant”.
Results: studies show that conventional US is widely used to help predict the malignancy of TN. Individual US features cannot be used to make an accurate diagnosis of thyroid cancer. Cystic content and spongiform appearance, however, might estimate the presence of benign nodules, but the clinical applicability of these features is limited due to their infrequent occurrence. Since none of the US signs are considered pathognomonic, it is important to determine a correlation between them. [3, 9] The use of different US methods, when evaluating TN, improve the diagnostic value.  SE and SWE are used in clinical practice to evaluate TN by comparing tissue elasticity. FNA biopsy is one more diagnostic method, which plays a major role in the differentiation between benign and malignant TN.  The diagnostic accuracy of US-FNA for TN varies, ranging from 60% to 96%. 
Conclusions: evidence suggests that individual US features cannot be used to confirm thyroid cancer. A combination of conventional US and other methods, such as SE, SWE and FNA have a major impact on the diagnostic value and facilitate the differentiation between benign and malignant TN.
Keywords: thyroid nodule, ultrasonography, benign, malignant.
List of abbreviations
US – ultrasonography
FNA – fine needle aspiration
TN – thyroid nodule
SWE – shear-wave elastography
SE – strain elastography
FNA – fine-needle aspiration