有时，最初被视为良性的大型甲状腺结节在射频消融（radiofrequency ablation, RFA）后会重新生长，并被诊断为恶性肿瘤。本研究旨在评估最初被RFA视为良性的甲状腺结节的超声特征及其后被诊断为癌症的预测因素，并探讨避免对这些癌症进行RFA的方法。我们回顾了2008年2月至2016年11月期间接受RFA治疗的连续134名患者中共148个结节的病历，这些结节最初被超声引导活检诊断为良性。我们研究了RFA前结节的特征、RFA后随访时的变化和最终手术病理学结果。 在148个良性结节中，有36个（24.3%）发生了RFA后的结节再生长。其中有22个结节被手术切除，其中7个（占36个的19.4%）被确认为恶性。在这22个结节中，与良性结节相比，恶性结节的RFA前中位体积（范围）显著更大：22.4 ml（13.9-84.5） vs. 13.4 ml（7.3-16.8）（P = 0.04）。恶性结节和良性结节之间的再生长间隔没有显著差异（P = 0.49）。在12个月时，恶性结节的中位体积减小率（范围）显著低于良性结节：51.4%（0-57.8） vs. 83.8%（47.9-89.6）（P = 0.01）。所有七个恶性结节在RFA前经过两次超声引导的细针穿刺（fine-needle aspiration, FNA）证实为良性，除了一个结节，它通过超声引导的穿刺活检（core-needle biopsy, CNB）证实为恶性。再生长的恶性结节被CNB诊断为可疑滤泡性肿瘤。恶性结节的组织学检查揭示为滤泡性甲状腺癌，除了一个滤泡性变种乳头状甲状腺癌。 RFA后再生长或效果不佳的症状性大型良性甲状腺结节可能具有恶性潜力。使用CNB而非FNA对这些结节的确诊更好。 版权所有 © 2023 韩国放射学会。

Regrowth after radiofrequency ablation (RFA) of symptomatic large thyroid nodules, initially treated as benign, sometimes turns out to be malignancies. This study aimed to assess the ultrasound (US) characteristics of thyroid nodules initially treated as benign with RFA and later diagnosed as cancers, predictive factors for cancers masquerading as benign, and methods to avoid RFA in these cancers.We reviewed the medical records of 134 consecutive patients with 148 nodules who underwent RFA between February 2008 and November 2016 for the debulking of symptomatic thyroid nodules diagnosed as benign using US-guided biopsy. We investigated the pre-RFA characteristics of the thyroid nodules, changes at follow-up after RFA, and the final surgical pathology.Nodule regrowth after RFA was observed in 36 (24.3%) of the 148 benign nodules. Twenty-two of the 36 nodules were surgically removed, and malignancies were confirmed in seven (19.4% of 36). Of the 22 nodules removed surgically, pre-RFA median volume (range) was significantly larger for malignant nodules than for benign nodules: 22.4 (13.9-84.5) vs. 13.4 (7.3-16.8) mL (P = 0.04). There was no significant difference in the regrowth interval between benign and malignant nodules (P = 0.49). The median volume reduction rate (range) at 12 months was significantly lower for malignant nodules than for benign nodules (51.4% [0-57.8] vs. 83.8% [47.9-89.6]) (P = 0.01). The pre-RFA benignity of all seven malignant nodules was confirmed using two US-guided fine-needle aspirations (FNAs), except for one nodule, which was confirmed using US-guided core-needle biopsy (CNB). Regrown malignant nodules were diagnosed as suspicious follicular neoplasms by CNB. Histological examination of the malignant nodules revealed follicular thyroid carcinomas, except for one follicular variant, a papillary thyroid carcinoma.Symptomatic large benign thyroid nodules showing regrowth or suboptimal reduction after RFA may have malignant potential. The confirmation of these nodules is better with CNB than with FNA.Copyright © 2023 The Korean Society of Radiology.