Differential diagnosis of diffuse sclerotic thyroid papillary carcinoma and Hashimoto's thyroiditis using fine‐needle aspiration cytology, BRAF(V600E), and ultrasound elastography

BACKGROUND: The diffuse sclerosing variant of papillary thyroid carcinoma (DSV‐PTC) has ultrasound findings that are similar to Hashimoto's thyroiditis (HT), resulting in under‐diagnosis. DSV‐PTC combined with HT is also common, so early and accurate diagnosis of DSV‐PTC using a variety of diagnostic techniques, including FNAC, BRAF(V600E) mutation detection, and ultrasound elastography, is critical. OBJECTIVE: To assess the diagnostic value of fine‐needle aspiration cytology (FNAC) and BRAF(V600E) detection in combination with ultrasound elastography in the diagnosis of DSV‐PTC. METHODS: We performed a retrospective analysis of 40 patients with pathologically confirmed DSV‐PTC and 43 patients with HT admitted to our hospital's ultrasound department between January 2015 and December 2020. Preoperative FNAC, BRAF(V600E) mutation detection, and ultrasound elastography imaging were all performed on all patients. For a definitive diagnosis, the results of these tests were compared to postoperative pathological findings. The diagnostic value of FNAC, BRAF(V600E) mutation detection, ultrasound elasticity imaging, and their combination for DSV‐PTC diagnosis was assessed. RESULTS: The mean elastic strain rate ratio (E1/E2) of the 40 DSV‐PTC cases was 5.75 ± 2.14, while that of the 43 HT cases was 2.81 ± 1.20. The receiver operating characteristic (ROC) curve was generated using the average value of E2/E1. The area under the ROC curve was 0.910, and the optimal E2/E1 cut‐off value was 4.500. When FNAC, BRAF(V600E) mutation detection, and ultrasound elasticity imaging detection were combined, the diagnostic sensitivity, specificity, negative predictive value, positive predictive value, and accuracy of DSV‐PTC diagnosis were 92.5%, 95.3%, 93.2%, 94.9%, and 94.0%, respectively, which were significantly higher than the single technique (p < 0.05). CONCLUSIONS: The use of FNAC, BRAF(V600E) mutation detection, and ultrasound elastography in combination is more helpful in establishing an accurate diagnosis of DSV‐PTC than using a single diagnostic technique alone.