Bilateral papillary thyroid cancer: Pitfalls of ACR TI-RADS and evaluation of modified parameters

AbstractPurpose To explore modified parameters for The ACR Thyroid Imaging Reporting and Data System (TI-RADS) of contralateral nodules based on preoperative ultrasound features of suspected-lobe papillary thyroid carcinoma (PTC), to assist managing bilateral PTC. Methods 389 consecutive PTC patients (272 in training set and 117 in validation set) who underwent total thyroidectomy in our center were retrospectively analyzed from March 2020 to March 2022. According to postoperative pathological data, the patients were divided into unilateral and bilateral PTC group. The clinicopathological features and sonographic characteristics of suspected nodules were compared between the two groups and further ultrasonic characteristics of underestimated nodules were analyzed. Results Patients with BMI ≥ 25 kg/m2, multifocality in suspected-lobe, isthmus nodule with TI-RADS classification > 3 tended to have bilateral PTC (P < 0.001, P < 0.001, and P = 0.03, respectively). After modifying ACR TI-RADS classification of contralateral nodules using the above three parameters, AUC for diagnosing contralateral lesions increased from 0.79 (95%CI: 0.74–0.84) to 0.83 (0.78–0.87) in training set. Missed-diagnosis rate of contralateral PTCs were both decreased in training set [21.1% (28/133) to 4.5% (6/133)] and validation set [11.4% (8/70) to 2.9% (2/70)]. In addition, the presence of cystic components and halo sign in contralateral nodules tend to be underestimated by ultrasound preoperatively, with underestimation rates of 100% (6/6) and 73.3% (11/15), respectively. Conclusion The modified ACR TI-RADS classification based on suspected-lobe may be an effective method for preoperative malignant risk stratification of contralateral nodules in patients with bilateral PTCs, which can avoid inadequate surgical extent.