Diagnostic performance of ACR-TIRADS combined with superb microvascular imaging for differential diagnosis of mummified thyroid nodules and papillary thyroid carcinomas.

OBJECTIVE: To investigate the ability of superb microvascular imaging (SMI) to improve the differential diagnosis of mummified thyroid nodules (MTNs) and papillary thyroid carcinomas (PTCs) using the 2017 American College of Radiology Thyroid Imaging Reporting and Data System (ACR-TIRADS).

MATERIALS AND METHODS: We enrolled 110 cases of MTNs and 110 cases of PTCs confirmed by fine-needle aspiration (FNA) or surgery. Conventional ultrasound (US) and SMI were analyzed for all nodules. Thyroid nodules were initially categorized by ACR-TIRADS and ACR-TIRADS combined with SMI (SMI-TIRADS). We compared the diagnostic performances of ACR-TIRADS and SMI-TIRADS by receiver operating characteristic curve, sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV).

RESULTS: US-detected margin, shape, and echogenic foci differed between MTNs and PTCs (P<0.05). The SMI blood-flow grade was greater in PTCs compared with MTNs (c2=158.78, P<0.05). There was no significant difference in ACR-TIRADS indicators between MTNs and PTCs (c2=1.585, P=0.453); reclassification by SMI-TIRADS showed significant differences between the groups (c2=129.521, P<0.001). The area under the curve was lower for ACR-TIRADS compared with SMI-TIRADS (0.517 vs 0.887, P<0.05). SMI-TIRADS had higher diagnostic value for distinguishing MTNs and PTCs than ACR-TIRADS (sensitivity: 91.82% vs 74.55%, P<0.05; specificity: 84.55% vs 21.82%, P<0.05; accuracy: 88.18% vs 48.18%, P<0.05; PPV: 85.59% vs 48.81%, P<0.05; NPV: 91.18% vs 46.15%, P<0.05).

CONCLUSION: The detection of micrangium and large vessels in thyroid nodules by SMI resulted in high diagnostic specificity and sensitivity. ACR-TIRADS combined with SMI could effectively distinguish between MTNs and PTCs, to avoid unnecessary FNA or surgery.