Can ultrasound be as a surrogate marker for diagnosing a papillary thyroid cancer? Comparison with BRAF mutation analysis

Abstract

Purpose: We investigated the merit of ultrasound (US) features and BRAF(V600E) mutation as an additional study of cytology and compared the diagnostic performances of cytology alone, cytology with US correlation, cytology with BRAFV600E mutation, and a combination of cytology, US, and BRAFV600E mutation all together.

Materials and methods: This study included 185 patients (mean age, 48.4 years; range 20-77 years) with 191 thyroid nodules who underwent US-guided fine-needle aspiration (FNA) with an additional BRAFV600E mutation test. Three radiologists highly experienced in thyroid imaging retrospectively reviewed US images and classified each nodule into two categories (positive for malignancy or negative for malignancy). Interobserver variability (IOV) of US assessment between the three readers was estimated using the generalized kappa statistic of Landis and Koch. We also calculated the diagnostic performances of these studies.

Results: There were 131 cases of malignancy (131/191, 68.6%) and 60 cases of benign nodules (60/191, 31.4%). In terms of IOV of US assessment, the generalized kappa value was 0.242, indicating fair agreement was reached. The combination of cytology with BRAFV600E showed higher specificity (100%) and positive predictive value (PPV) (100%) compared to the combination of cytology, BRAFV600E, and US (specificity 28.3%, 66.7%, 68.3%; PPV 74.6%, 86.6%, 86.8%, respectively; p<0.001). However, cytology with BRAFV600E showed lower sensitivity (84.7%) than cytology with BRAFV600E and US (96.2%, 98.5%, 95.4%, respectively; p<0.001).

Conclusion: Considering the diagnostic performance and low reproducibility of US, the combination of FNA with BRAFV600E is the most reliable and objective method for diagnosing thyroid malignancy.

Keywords: BRAF mutation; Thyroid cancer; thyroid ultrasound.

Fig. 1

Diagram of study group. US, ultrasound; F/U, follow-up.