Analysis of ultrasonographic characteristics of benign thyroid nodules misdiagnosed as thyroid carcinoma: sonography-pathology correlation

Objective To analyze the ultrasound features of ultrasonograpy-false-positive benign thyroid nodules in 37 cases. Methods With pathology results as the golden standard, thirty-seven patients with forty-six nodules were misdiagnosed as thyroid cancer by ultrasonography. The pre-operative diagnosis of ultrasonography were retrospectively reviewed and analyzed. Results Among forty-six thyroid nodules, twenty-one nodules had a diameter of 10.0 mm or smaller, while the other twenty-five nodules had a diameter of larger than 10.0 mm. In all forty-six thyroid nodules, the pre-operative ultrasonography found the majority of nodules with 3 or more than 3 malignant signs. The forty-six thyroid nodules showed solid (89.1%, 41/46), cystic-solid (10.9%, 5/46), marked hypoechogencity (87.0%, 40/46), ill-defined margin (56.5%, 26/46), calcification (76.1%, 35/46), microcalcification and macrocalcification), and taller-than-wide shape (30.4%, 14/46). The thyroid imaging reporting and data system (TI-RADS) lexicon was introduced to describe the lesions: forty-one nodules were categorized as TI-RADS 4c and 5 nodules were categorized as TI-RADS 5. On histology, these misdiagnosed thyroid nodules revealed severe fibrosis, hyalinization and calcification. The ultrasonic images were complicated and difficult to be differentiated from thyroid cancer. Conclusion Benign thyroid nodules with fibrosis, hyalinization, hemorrhage and calcification will lead to the significant change on lesions' morphology, echo intensity and internal structure. When the benign and malignant signs ultrasound co-existed in a single thyroid nodule, benign thyroid nodules might be easily misdiagnosed as thyroid cancer. Key words: Ultrasonography; Diagnostic errors; Thyroid nodule; Pathology