[Value of modified TI-RADS in the diagnosis of medullary thyroid carcinoma]

Objective: To investigate the value of modified thyroid imaging reporting and data system (TI-RADS) in the sonographic diagnosis of medullary thyroid carcinoma (MTC), and to evaluate the sonographic differences among MTC, papillary thyroid carcinoma (PTC) and benign nodules in order to improve the ultrasound diagnostic accuracy of MTC. Methods: 646 cases of thyroid lesions confirmed by pathology in our hospital were divided into the MTC group (64 cases), PTC group (414 cases) and benign group (168 cases). The ultrasonographic characteristics of these groups were retrospectively analyzed. All of the 646 cases were classified by modified TI-RADS grading criteria. The diagnostic accuracy of MTC and ultrasonic manifestations of MTC, PTC and benign nodular were assessed. Results: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of modified TI-RADS for MTC were 87.5%, 89.9%, 72.6%, 88.8%, and 67.2%, respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of modified TI-RADS for PTC were 96.1%, 59.5%, 85.4%, 86.2% and 85.6%. The intraclass correlation coefficient (ICC) of three different physicians for thyroid nodules was 0.983 by the modified TI-RADS. MTC were mostly located in middle and upper parts of the thyroid (85.9%, 55/64), hypoechoic or extremely hypoechoic (89.1%, 57/64), with relatively smooth margin (35.9%, 23/64), aspect ratio<1 (53.1%, 34/64), abundant blood flow (31.2%, 20/64), and high lymph node metastasis rate (51.6%, 33/64). These differences were statistically significant when compared to PTC (P<0.05). Conclusions: Repeatability of modified TI-RADS for MTC was high, and is slightly lower than that for PTC. MTC had specific features: mostly located in middle and upper parts of the thyroid, hypoechoic or extremely hypoechoic, relatively smooth margin, aspect ratio<1, abundant blood flow and high lymph node metastasis rate.