The value of ultrasound elastography in differentiation of malignancy in thyroid nodules

Abstract

We aimed to determine the value of ultrasound elastography (US-E) using carotid artery pulsation in differentiation of malignant and benign thyroid nodules. One hundred ten nodules were evaluated by US-E, and stiffness scores were compared to biopsy results. When cutoff for malignancy was determined as score 4, sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 95%, 40%, and 100%, respectively. We suggest fine needle aspiration biopsy to be performed in all score 4 nodules, while biopsy may be unnecessary in score 1 nodules. Benign biopsy result in a score 4 nodule should suggest radiological–pathological disagreement, and repeat biopsy should be recommended.

Introduction

Thyroid gland nodules are common, and palpable nodules are found in between 4% and 7% of the adult population [1], [2]. Widespread use of ultrasound (US) imaging and development of high-resolution scanners have significantly improved the detection of thyroid nodules [2]. According to US imaging and autopsy results, the incidence of thyroid nodules may increase up to 50% of population [3], [4], [5]. The rate of malignancy among thyroid nodules range between 5% and 15% [6], [7]. US imaging is a definitive method for detection of thyroid nodules; however, the predictive value of US in differentiation of malignant nodules is limited [8], [9]. Currently, the best available method for discrimination of malignant from benign thyroid nodules is fine needle aspiration biopsy (FNAB) [10], [11], [12]. Despite its high sensitivity and specificity, FNAB is an invasive procedure and may give nondiagnostic results in 10% to 20% of biopsies [6].

Palpation is clinically used to evaluate the stiffness of a thyroid nodule; however, it is a subjective method, and findings depend on the size and location of the nodule as well as the examiner’s skill [13]. Elastography is a recently introduced noninvasive technique which estimates the stiffness of tissues by assessing distortion under compression [14], [15]. US elastography has been successfully applied in the breast and more recently in the prostate gland [16]. Previous ex vivo and in vivo studies have documented significant differences in stiffness of normal thyroid tissue and tumors of the thyroid gland [17], [18]. However, out-of-plane motion of the nodule during external compression and compression of the thyroid gland due to pulsation of the carotid artery may limit this technique [17]. Carotid pulsation has also been used as a source of compression for elastography of the thyroid gland [19], [20].

In this study, we aimed to determine the diagnostic value of US elastography in the differentiation of malignant and benign thyroid nodules using carotid artery pulsation as the source of compression.