OBJECTIVE To present the sonographic follow-up of intrathyroidal ectopic thymus (IET) in children and adolescent patients. PATIENTS Out of the 507 children referred to FNAB between 2006 and 2018, 30 (5.9%) pediatric patients (10 females), mean age 5.7 years (1.2-13.8, median 4.9 years) were diagnosed with IET. METHODS A retrospective analysis of medical files of patients diagnosed with IET between 2006 and 2018. Assessed data included ultrasound characterisation, elastographic strain ratio (SR) results and hormonal evaluation. RESULTS Analysis of thyroid US scans revealed that the mean age at the first thyroid ultrasound was 5.7 (1.2-13.8, median 4.9) years, and at the last US 10.7 (3.7-18, median 10.5) years. The mean time of the IET observation was 59.6 (2-148, median 53.5) months. On US, IET was hypoechoic with multiple linear and punctate echoes, hypovascular, fusiform on longitudinal plane and round or polygonal on an axial plane, more common in the right thyroid lobe (66.7%) and located in the posterior part of the lobes (54.5%), bilateral in two patients and multifocal in one patient. SR of IET was similar to the surrounding normal thyroid tissue. Complete regression of IET was observed in 12/30 patients after a mean time of 81.7 months (median 76.5), at the mean age of 13.7 (9.2-18, median 13.9) years. FNAB was performed in 10/30 and a hemithyroidectomy in 1/30 IET patients. In the FNAB (+) group, patients were younger (5.08 vs 6.08 years) and lesions were larger (0.12 ml vs 0.05 ml) than in the FNAB (-) group. All patients with IET were euthyroid with negative TPOAb and TgAb levels. CONCLUSION The reproducibility of unique ultrasound features of IETs allows for safe long-term follow-up of these benign lesions in the majority of pediatric patients: not only monitoring the regression of IET but also screening towards the rare occurrence of a tumor arising from the IET.

中文翻译：

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儿童甲状腺内异位胸腺的长期超声随访。

目的对儿童和青少年患者的甲状腺内异位胸腺（IET）进行超声检查。患者2006年至2018年间转诊至FNAB的507名儿童中，有30名（5.9％）儿科患者（10名女性），平均年龄5.7岁（1.2-13.8岁，中位数4.9岁）被诊断为IET。方法回顾性分析2006年至2018年间诊断为IET的患者的医疗档案。评估的数据包括超声表征，弹性成像应变比（SR）结果和激素评估。结果对甲状腺US扫描的分析显示，第一次甲状腺超声检查的平均年龄为5.7（1.2-13.8，中位数4.9）岁，最近的US 10.7（3.7-18，中位数10.5）岁。IET观察的平均时间为59.6（2-148，中位数为53.5）个月。在美国，IET是低回声的，具有多个线性和点状回声，在纵向平面上为低血管，梭形，在轴向平面上为圆形或多边形，在甲状腺右叶（66.7％）中更常见，位于叶的后部（54.5％），双侧2例，多灶1例。IET的SR类似于周围的正常甲状腺组织。在平均时间81.7个月（中位数76.5），平均年龄13.7（9.2-18，中位数13.9）岁之后，在12/30患者中观察到IET完全消退。FNAB在10/30进行，半甲状腺切除术在I / 30的患者中进行。在FNAB（+）组中，患者比FNAB（-）组年轻（5.08 vs 6.08岁），病变更大（0.12 ml vs 0.05 ml）。所有IET患者均为甲状腺功能正常，且TPOAb和TgAb阴性。