Shear wave elastography in the evaluation of level VI lymph nodes in papillary thyroid carcinoma: combined with gray-scale ultrasound ex vivo

BACKGROUND: The evaluation of cervical lymph nodes is very important for patients with papillary thyroid carcinoma (PTC). Conventional ultrasound is recommended to assess the status of cervical lymph nodes but the diagnostic performance is not satisfying especially in level VI lymph nodes. Recently, shear wave elastography has shown great potential in diagnosis. Therefore, this study aimed at exploring the value of shear wave elastography in ultrasound evaluation for level VI lymph nodes in papillary thyroid carcinoma. Because Hashimoto’s thyroiditis may influence the diagnostic performance, a subgroup was also analysed that included only lymph nodes from PTC without Hashimoto’s thyroiditis. METHODS: Eighty-Seven level VI lymph nodes from 22 consecutive patients with papillary thyroid carcinoma were evaluated by gray-scale ultrasound and SWE in condition of ex vivo before rapid frozen section. Gray-scale ultrasound and shear wave elastography indexes of metastatic and non-metastatic lymph nodes were evaluated by statistical analysis separately in all patients and in patients without Hashimoto’s thyroiditis. Indexes included long diameter, short diameter, short-to-long diameter ratio (S/L ratio), E(mean), E(min), E(max) and E(SD). The rapid frozen section result of each lymph node was used as gold standard to evaluate the diagnostic performance of gray-scale ultrasound and combination method which combined gray-scale ultrasound and SWE. RESULTS: In all patients, significant indexes included short diameter (p = 0.009), S/L ratio (p = 0.003), E(max) (p = 0.016) and E(SD) (p = 0.006). In patients without Hashimoto’s thyroiditis, significant indexes included short diameter (p = 0.002), S/L ratio (p = 0.003), E(mean) (p = 0.030), E(max) (p < 0.001) and E(SD) (p = 0.001). Combining gray-scale ultrasound with SWE, combination method had higher AUC than gray-scale ultrasound both in all patients (0.887 vs 0.841) and patients without Hashimoto’s thyroiditis (0.925 vs 0.866). Gray-scale ultrasound had higher AUC in patients without Hashimoto’s thyroiditis than in all patients (0.866 vs 0.841), which was the same with combination method (0.925 vs 0.887). CONCLUSION: Shear wave elastography can provide additional information for ultrasound evaluation of level VI lymph nodes in papillary thyroid carcinoma, especially in papillary thyroid carcinoma without Hashimoto’s thyroiditis.