Sonographic appearances of intrathyroid thymus: emphasis on details

Maria Raissaki, Ioanna Tritou, Penelope Smirnaki

Abstract


Purpose: To thoroughly describe ultrasonographic findings of intrathyroid thymus including characteristics that have not been previously emphasised.

Material and Methods: Forty-six children aged 21 days-14 years (mean 5.8 years) underwent cervical ultrasonography. Diagnosis of intrathyroid thymus was based on comparison with visible mediastinal thymus and follow-up in all patients, MRI in 2 and needle biopsy in 1 child.

Results: Fifty-two lesions <0.9 cm were identified, 29 (55.8%) left-sided; fifty-one (98.1%) at the lower 2/3 of the respective lobe on sagittal images. No lesion was situated anteriorly on transverse scans. Forty-three (82.7%) lesions exhibited angulated borders at either axial and/or transverse images producing a geographic shape while 9 (17.3%) were round/ovoid at all images. Thirty-six (73%) lesions reached the thyroid’s capsule and 14 were peripheral, within 1-3 mm (mean 2.1 mm) from it. Eighteen (34.6%) lesions exhibited extrathyroid extension and 13 (25%) connecting tissue with mediastinal thymus. Echopattern was identical to the same patient’s thymus: hypo-or iso-echoic to the thyroid, containing bright scattered spots in all lesions. Forty-nine (94.2%) lesions exhibited a spared thin hypoechoic rim. Colour Doppler over 31 lesions showed no/sparce vascularity.

Conclusions: The starry-sky pattern with sparing of a thin peripheral rim, identical to the individual’s mediastinal thymus, was seen in 94.2% of intrathyroid thymus. Prevalent characteristics also included no/sparce vascularity, geographic elongated shape, angulated borders, as well as occasional extrathyroidal extension and connecting thymic tissue between the thyroidal and mediastinal thymus. These appearances, when seen in small posterior/caudal lesions, prompted conservative follow-up instead of invasive management.


Keywords


thyroid; ultrasonography; child; intrathyroid thymus; ectopic thymus

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References


Millman B, Pelutteri PK. Nodular thyroid disease in children and adolescents. Otolaryngol Head Neck Surg 1997; 116 (6): 604-609.

Niedziela M. Pathogenesis, diagnosis and management of thyroid nodules in children. Endocr Relat Cancer 2006; 13(2): 427-453.

Gupta A, Ly S, Castroneves, et al. A standardized assessment of thyroid nodules in children confirms higher cancer prevalence than in adults. J Clin Endocrinol Metab 2013; 98(8): 3238-3245.

Goldfarb M, Gondek SS, Sanchez Y, et al. Clinic-based ultrasound can predict malignancy in pediatric thyroid nodules. Thyroid 2012; 22(8): 827-831.

Avula S, Daneman A, Navarro OM, et al. Incidental thyroid abnormalities identified on neck US for non-thyroid disorders. Pediatr Radiol 2010; 40(11): 1774-1780.

Kabaalioğlu A, Öztek MA, Kesimal U, et al. Intrathyroidal ectopic thymus in children: a sonographic survey. Med Ultrason 2017; 19(2): 179-184.

Kim HG, Kim MJ, Lee MJ. Sonographic appearance of intrathyroid ectopic thymus in children. J Clin Ultrasound 2012; 40(5): 266-271.

Nam BD, Chang YW, Hong SS, et al. Characteristic sonographic and follow Up features of thyroid nodules according to childhood age groups. J Korean Soc Radiol 2016; 75(2): 126-132.

Fukushima T, Suzuki S, Ohira T, et al. Prevalence of ectopic intrathyroidal thymus in Japan: the Fukushima health management survey. Thyroid 2015; 25(5): 534-537.

Megremis S, Stiakaki E, Tritou I, et al. Ectopic intrathyroidal thymus misdiagnosed as a thyroid nodule: sonographic appearance. J Clin Ultrasound 2008; 36(7): 443-447.

Segni M, di Nardo R, Pucarelli I, et al. Ectopic intrathyroidal thymus in children: a long-term follow-up study. Horm Res Paediatr 2011; 75(4): 258-263.

Koumanidou C, Vakaki M, Theophanopoulou M, et al. Aberrant thymus in infants: sonographic evaluation. Pediatr Radiol 1998; 28(12): 987-989.

Gimm O, Krause U, Wessel H, et al. Ectopic intrathyroidal thymus diagnosed as a solid thyroid lesion: case report and review of the literature. J Pediatr Surg 1997; 32(8): 1241-1243.

Büyükyavuz I, Otçu S, Karnak I, et al. Ectopic thymic tissue as a rare and confusing entity. Eur J Pediatr Surg 2002; 12(5): 327-329.

Courcoutsakis N, Patronas N, Filie AC, et al. Ectopic thymus presenting as a thyroid nodule in a patient with the Carney complex. Thyroid 2009; 19(3): 293-296.

Hernandez-Cassis C, Poniecka A, Vogel CK, et al. A six-year-old boy with a suspicious thyroid nodule: intrathyroidal thymic tissue. Thyroid 2008; 18 (3): 377-381.

Cacciaguerra S, Rizzo L, Tranchina MG, et al. Ultrasound features of ectopic cervical thymus in a child. Pediatr Surg Int 1998; 13(8): 597-599.

Lignitz S, Musholt TJ, Kreft A, et al. Intrathyroidal thymic tissue surrounding an intrathyroidal parathyroid gland, the cause of a solitary thyroid nodule in a 6-year-old boy. Thyroid 2008; 18(10): 1125-1130.

Segni M, Nuti F, di Nardo R. Ectopic intrathyroidal thymus in an 11-year-old boy. Thyroid 2006; 16(11): 1179-1180.

Park SH, Ryu CW, Kim GY, et al. Intrathyroidal thymic tissue mimicking a malignant thyroid nodule in a 4-year-old child. Ultrasonography 2014; 33(1): 71-73.

Vlachopapadopoulou EA, Vakaki M, Karachaliou FE, et al. Ectopic intrathyroidal thymus in childhood: a sonographic finding leading to misdiagnosis. Horm Res Paediatr 2016; 86(5): 325-329.

Patel MN, Komlos M, Racadio JM. Intrathyroidal thymic tissue mimicking a thyroid nodule in a 4-year-old child. J Clin Ultrasound 2013; 41(5): 319-320.

Yildiz AE, Ceyhan K, Sıklar Z, et al. Intrathyroidal ectopic thymus in children: retrospective analysis of grayscale and Doppler sonographic features. J Ultrasound Med 2015; 34(9): 1651-1656.

Chu WC, Metreweli C. Ectopic thymic tissue in the paediatric age group. Acta Radiol 2002; 43(2): 144-146.

Wiersinga WM. Management of thyroid nodules in children and adolescents. Hormones (Athens) 2007; 6(3): 194-199.

Babcock DS. Thyroid disease in the pediatric patient: emphasizing imaging with sonography. Pediatr Radiol 2006; 36(4): 299-308.

Aguayo-Figueroa L, Golightly MG, Hu Y, et al. Cytology and flow cytometry to identify ectopic thymic tissue masquerading as a thyroid nodule in two children. Thyroid 2009; 19(4): 403-406.

Durmaz E, Barsal E, Parlak M, et al. Intrathyroidal ectopic thymic tissue may mimic thyroid cancer: a case report. J Pediatr Endocrinol Metab 2012; 25(9-10): 997-1000.

Harach HR, Vujanic GM. Intrathyroidal thymic tissue: an autopsy study in fetuses with some emphasis on pathological implications. Pediatr Pathol 1993; 13(4): 431-434.

Yildiz AE, Elhan AH, Fitoz S. Prevalence and sonographic features of ectopic thyroidal thymus in children: a retrospective analysis. J Clin Ultrasound 2018 ; 46(6): 375-379.

Han BK, Suh YL, Yoon HK. Thymic ultrasound. I. Intrathymic anatomy in infants. Pediatr Radiol 2001; 31(7): 474-479.

Han BK, Yoon HK, Suh YL. Thymic ultrasound. II. Diagnosis of aberrant cervical thymus. Pediatr Radiol 2001; 31(7): 480-487.

Nishino M, Ashiku SK, Kocher ON, et al. The thymus: a comprehensive review. Radiographics 2006; 26(2): 335-348.

Nasseri F, Eftekhari F. Clinical and radiologic review of the normal and abnormal thymus: pearls and pitfalls. Radiographics 2010; 30(2): 413-428.

Corrias A, Mussa A. Thyroid nodules in pediatrics: which ones can be left alone, which ones must be investigated, when and how. J Clin Res Pediatr Endocrinol 2013; 5 Suppl 1: 57-69.

Martinez-Rios C, Daneman A, Bajno L, et al. Utility of adult-based ultrasound malignancy risk stratifications in pediatric thyroid nodules. Pediatr Radiol 2018; 48(1): 74-84.

Solbiati L, Osti V, Cova L, et al. Ultrasound of thyroid, parathyroid glands and neck lymph nodes. Eur Radiol 2001; 11(12): 2411-2424.

Saggese D, Ceroni Compadretti G, Cartaroni C. Cervical ectopic thymus: a case report and review of the literature. Int J Pediatr Otorhinolaryngol 2002; 66(1): 77-80.

Cohen JB, Troxell M, Kong CS, et al. Ectopic intrathyroidal thymoma: a case report and review. Thyroid 2003; 13(3): 305-308.

Chan JK, Rosai J. Tumors of the neck showing thymic or related branchial pouch differentiation: a unifying concept. Hum Pathol 1991; 22(4): 349-367.

Tong GX, Hamele-Bena D, Wei XJ, et al. Fine-needle aspiration biopsy of monophasic variant of spindle epithelial tumor with thymus-like differentiation of the thyroid: report of one case and review of the literature. Diagn Cytopathol 2007; 35(2): 113-119.

Magnata Filho LA, Bordallo MA, Pessoa CH, et al. Thyroid spindle epithelial tumor with thymus-like differentiation (SETTLE): case report and review. Arq Bras Endocrinol Metabol 2010; 54(7): 657-662.

Frates MC, Benson CB, Dorfman DM, et al. Ectopic intrathyroidal thymic tissue mimicking thyroid nodules in children. J Ultrasound Med 2018; 37(3): 783-791.




DOI: http://dx.doi.org/10.36162/hjr.v3i2.227

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