Ectopic intrathyroidal thymus in children: Prevalence, imaging findings and evolution

Abstract

Erol OB, Şahin D, Bayramoğlu Z, Yılmaz R, Akpınar YE, Ünal ÖF, Yekeler E. Ectopic intrathyroidal thymus in children: Prevalence, imaging findings and evolution. Turk J Pediatr 2017; 59: 387-394. The aim of this study was to evaluate the ultrasound (US) features of intrathyroidal ectopic thymus (IET) and demonstrate the alterations after follow-up. This study included 36 lesions of 32 patients (mean age 95 ± 58 months) diagnosed with IET. The patients underwent follow-up US examination at least 22-months without a medication or surgical intervention. A total of 36 IETs with an incidence of 0.91% were detected among 3914 thyroid ultrasound (US) examinations. The mean of anteroposterior (ap), transverse (tr), and craniocaudal (cc) diameters in the initial US examinations were 3.1±1.19 mm, 4.89±1.86 mm, and 6.45±3.92 mm respectively. All of the lesions were well-demarcated, hypoechoic to the thyroid gland, and contained uniformly distributed punctate echogenic foci. Follow-up US examinations were performed after 684±85 days. The alterations between the initial and follow-up diameters for ap and cc direction were not statistically significant. However, a significant difference (p=0.007) was found for transverse diameters and the IETs were found to be smaller at follow-up US than in the initial US. Most of the IETs were located in the left lobe (64%), middle portion (83%), and extended to a border of thyroid gland (69%) and nonspherical in shape (89%). The descriptive findings of IETs are uniform distribution of punctate echogenic foci, absence of a rim, and the presence of vessels traversing through the lesion without parenchymal displacement. Given our findings, healthcare professionals should be aware of the diagnosis of IET. Patients with an IET could be safely managed with follow-up US and any surgical treatment would not be required.

Prevalence of cervical extension of the thymus in children

“…The defects in thymus migration may cause the thymus to become ectopically located, either partly or totally, as seen mostly in the cervical region. The extension of the thymus to the inferior border of the thyroid gland is frequently observed in routine neck US examinations, especially during the inspiratory phase [ 10 ]. However, the cervical extension of the thymus may be mistaken for a soft tissue mass in the neck, particularly in children and young adults, potentially leading to unnecessary surgery and increased medical costs [ 3 , 4 ].…”

Phantom Nodules Detected by Ultrasound Examination of the Neck: The Possibility of Ectopic Cervical Thymic Tissue in Adults

“…When the thymus has not fully descended into the mediastinum, thymic tissue can be found in the neck 7 8 9 . Several authors have described the US characteristics of ETT 7 8 9 10 11 12 13 14 15 16 17 . According to their reports, the lesions are well-defined, angular, solid nodules with multiple inner echogenic foci and linear structures.…”

The Role of Superb Microvascular Imaging and Shear Wave Elastography in Differentiation of Thyroid Nodules from Intrathyroidal Ectopic Thymus in Children

“…IET has previously been reported as a very common incidental finding in children as 2.6 % in a survey of thyroid glands of 350 infants and necropsies (4). The incidence of IET has been found to be 0.91% to 17.3% in other recent studies (5)(6)(7). The imaging properties of IETs detected on grayscale ultrasonography are widely known among pediatric radiologists.…”

“…Consecutive 27 children (17 female, 10 male; median age: 15.6 years (range: 10-18) with thyroid nodules and 20 children with IETs (14 male, 6 female; median age: 8.8 years (range: [3][4][5][6][7][8][9][10][11][12][13][14] were evaluated between August 2017 and August 2018 in the Pediatric Radiology Department. The local ethics committee approved the study (Approval number: 2018/703 ) and informed consent from the legal guardians of the patients was obtained.…”

“…However, IETs detected in centers with limited experience in this field can be misdiagnosed as thyroid nodules and these lesions can be referred for fine-needle aspiration biopsy even if they do not require follow-up. There have been descriptive imaging findings addressing IET diagnosis qualitatively (5)(6)(7)(8). However, insufficient data are showing that it is possible to distinguish IET and thyroid nodules in children, quantitatively.…”