The Value of Microvascular Imaging for Triaging Indeterminate Cervical Lymph Nodes in Patients with Papillary Thyroid Carcinoma

SIMPLE SUMMARY: Papillary thyroid carcinomas (PTC) are indolent tumors associated with excellent long-term survival, albeit frequently accompanied by cervical lymph node (LN) metastasis. The imaging criteria using conventional ultrasound (US) techniques showed high diagnostic performance for the suspicious and probably benign LN categories, but showed low diagnostic performance for the indeterminate category. In this retrospective study, we aimed to assess the added value of Superb Microvascular Imaging (SMI) for detecting metastatic PTC in the indeterminate LN category. We confirmed that SMI could effectively stratify indeterminate LNs by visualizing additional vascular signals. The reclassified categories of SMI provided a high diagnostic performance to distinguish metastasis from benign LNs. Therefore, adding SMI to conventional US scans can be useful when evaluating indeterminate LNs in patients with PTC. ABSTRACT: Assessment of lymph node (LN) status in patients with papillary thyroid carcinoma (PTC) is often troublesome because of cervical LNs with indeterminate US (ultrasound) features. We aimed to explore whether Superb Microvascular Imaging (SMI) could be helpful for distinguishing metastasis from indeterminate LNs when combined with power Doppler US (PDUS). From 353 consecutive patients with PTC, LNs characterized as indeterminate by PDUS were evaluated by SMI to distinguish them from metastasis. Indeterminate LNs were reclassified according to the SMI, the malignancy risk of each category was assessed, and the diagnostic performance of suspicious findings on SMI was calculated. The incidence of US-indeterminate LNs was 26.9%. Eighty PDUS-indeterminate LNs (39 proven as benign, 41 proven as malignant) were reclassified into probably benign (n = 26), indeterminate (n = 20), and suspicious (n = 34) categories according to SMI, with malignancy risks of 19.2%, 20.0%, and 94.1%, respectively. After combining SMI with PDUS, 80.8% (21/26) of probably benign LNs and 94.1% (32/34) of suspicious LNs could be correctly diagnosed as benign and metastatic, respectively. The diagnostic sensitivity, specificity, and accuracy of categorizing LNs as suspicious based on SMI were 78.1%, 94.9%, and 86.3%, respectively. In conclusion, the combination of SMI with PDUS was helpful for the accurate stratification of indeterminate LNs based on US in patients with PTC.