Sonography Could Predict Complete/Near-Complete Necrosis of Thyroid Tumors After Fine-Needle Biopsy: Necrotic Ring Sign.

Objective: Necrosis, a rare histologic alteration caused by the fine-needle aspiration biopsy (FNA) of thyroid tumors, could be problematic in the clinical management of such cases due to the difficulty in making a definitive histopathologic diagnosis. The aim of this study was to define US features that may help to predict FNA-induced necrosis which is more common in oncocytic tumors.

Materials and methods: This cross-sectional study consists of all patients who underwent thyroid surgery in our center between January 2011 and December 2023. All nodules, which complete/near-complete necrosis reported on final histopathology, were included into study when full video record of preoperative US exam also available for re-evaluation. US findings of necrotic tumors compared with control group consisting of similar histopathology without necrosis.

Results: A total of 11 patients have met the inclusion criteria during study period. Of these cases, seven were papillary thyroid carcinomas and four were follicular adenomas. Among the evaluated distinctive US features, necrotic ring offers the best accuracy (88%) and area under the curve (0.91) values in detecting necrosis after FNA and most valuable when combined with lack of intranodular vascularity.

Conclusion: In the preoperative evaluation of surgical candidates, necrotic ring, refractive edge shadowing, posterior acoustic enhancement, and lack of vascular signal may predict complete/near-complete necrosis with great accuracy.