Korean Journal of Radiology

The Korean Society of Radiology (대한영상의학회)
권호 표지
DOI QR코드

DOI QR Code

Long-Term Follow-Up Ultrasonographic Findings of Intrathyroidal Thymus in Children

  • Yun-Woo Chang (Department of Radiology, Soonchunhyang University Hospital Seoul) ;
  • Hee Min Kang (Department of Radiology, Soonchunhyang University Hospital Seoul) ;
  • Eun Ji Lee (Department of Radiology, Soonchunhyang University Hospital Seoul)
  • Received : 2019.12.27
  • Accepted : 2020.04.06
  • Published : 2020.11.01
Download PDF
⟨ Previous Next ⟩

Abstract

Objective: To analyze long-term follow-up sonographic findings of intrathyroidal thymus in children. Materials and Methods: Among 1259 patients with congenital hypothyroidism under 15 years of age who underwent thyroid ultrasonography (US), 41 patients were diagnosed with an intrathyroidal thymus based on US criteria, i.e., hypoechoic solid lesion with punctate and linear echogenicity. In 26 patients aged one to 14 years old, the last follow-up US was performed after 6 to 132 months and compared with the initial US. The lesion was considered to decrease in size if there was a change of more than 2 mm in any dimension. The margin change was divided into well-defined and indistinct, blurred. When the echogenicity changed to a hyperechoic from a characteristic thymic echogenicity pattern, the pattern was considered a hyperechogenic. The changes in size were compared with the changes in shape, margin, and echogenicity pattern. The changes in size, shape, margin, and echogenicity were analyzed the association with the age of last follow-up. Statistical analysis was conducted using the chi-squared test and logistic regression. Results: Fifteen (57.7%) cases were stable in size, and 11 (42.3%) decreased in size, including one that disappeared. Ten (38.5%) cases changed to indistinct margins from initially well-defined margins including one case of initially indistinct margin. Six (23.1%) changed to hyperechogenic, from initially characteristic thymic echogenicity patterns. When follow-up change was compared, decreases in size were significantly associated with lesion changes to indistinct margins (p = 0.004). The age at last follow-up was significantly associated with change to hyperechogenicity (odd ratio, 2.141; 95% confidence interval, 1.144-4.010, p = 0.017). Conclusion: On follow-up US, an intrathyroidal thymus may be decreased in size, with indistinct margins, or show changes to a hyperechoic mass. Decreases in size may be associated with changing to indistinct margins, and changes to hyperechogenicity may be associated with increasing age.

Keywords

Acknowledgement

This work received Soonchunhyang University research funding.

References

  1. Avula S, Daneman A, Navarro OM, Moineddin R, Urbach S, Daneman D. Incidental thyroid abnormalities identified on neck US for non-thyroid disorders. Pediatr Radiol 2010;40:1774-1780
  2. Francis GL, Waguespack SG, Bauer AJ, Angelos P, Benvenga S, Cerutti JM, et al. Management guidelines for children with thyroid nodules and differentiated thyroid cancer. Thyroid 2015;25:716-759
  3. Shin JH, Baek JH, Chung J, Ha EJ, Kim JH, Lee YH, et al. Ultrasonography diagnosis and imaging-based management of thyroid nodules: revised Korean Society of Thyroid Radiology consensus statement and recommendations. Korean J Radiol 2016;17:370-395
  4. Yildiz AE, Ceyhan K, Siklar Z, Bilir P, Yagmurlu EA, Berberoglu M, et al. Intrathyroidal ectopic thymus in children: retrospective analysis of grayscale and doppler sonographic features. J Ultrasound Med 2015;34:1651-1656
  5. Kim HG, Kim MJ, Lee MJ. Sonographic appearance of intrathyroid ectopic thymus in children. J Clin Ultrasound 2012;40:266-271
  6. Segni M, di Nardo R, Pucarelli I, Biffoni M. Ectopic intrathyroidal thymus in children: a long-term follow-up study. Horm Res Paediatr 2011;75:258-263
  7. Gimm O, Krause U, Wessel H, Finke R, Dralle H. Ectopic intrathyroidal thymus diagnosed as a solid thyroid lesion: case report and review of the literature. J Pediatr Surg 1997;32:1241-1243
  8. Hernandez-Cassis C, Poniecka A, Vogel CK, McKenzie JM. A six-year-old boy with a suspicious thyroid nodule: intrathyroidal thymic tissue. Thyroid 2008;18:377-380
  9. Megremis S, Stiakaki E, Tritou I, Bonapart IE, Tsilimigaki A. Ectopic intrathyroidal thymus misdiagnosed as a thyroid nodule: sonographic appearance. J Clin Ultrasound 2008;36:443-447
  10. Patel MN, Komlos M, Racadio JM. Intrathyroidal thymic tissue mimicking a thyroid nodule in a 4-year-old child. J Clin Ultrasound 2013;41:319-320
  11. Kabaalioglu A, Oztek MA, Kesimal U, Ceken K, Durmaz E, Apaydin A. Intrathyroidal ectopic thymus in children: a sonographic survey. Med Ultrason 2017;19:179-184
  12. Stasiak M, Adamczewski Z, Stawerska R, Krawczyk T, Tomaszewska M, Lewin' ski A. Sonographic and elastographic features of extra- and intrathyroidal ectopic thymus mimicking malignancy: differential diagnosis in children. Front Endocrinol (Lausanne) 2019;10:223
  13. Frates MC, Benson CB, Dorfman DM, Cibas ES, Huang SA. Ectopic intrathyroidal thymic tissue mimicking thyroid nodules in children. J Ultrasound Med 2018;37:783-791
  14. Courcoutsakis N, Patronas N, Filie AC, Carney JA, Moraitis A, Stratakis CA. Ectopic thymus presenting as a thyroid nodule in a patient with the Carney complex. Thyroid 2009;19:293-296
  15. Bang MH, Shin J, Lee KS, Kang MJ. Intrathyroidal ectopic thymus in children: a benign lesion. Medicine (Baltimore) 2018;97:e0282
  16. Escobar FA, Pantanowitz L, Picarsic JL, Craig FE, Simons JP, Viswanathan PA, et al. Cytomorphology and sonographic features of ectopic thymic tissue diagnosed in paediatric FNA biopsies. Cytopathology 2018;29:241-246
  17. Yildiz AE, Elhan AH, Fitoz S. Prevalence and sonographic features of ectopic thyroidal thymus in children: a retrospective analysis. J Clin Ultrasound 2018;46:375-379
  18. Aydin S, Fatihoglu E, Kacar M. Intrathyroidal ectopic thymus tissue: a diagnostic challenge. Radiol Med 2019;124:505-509
  19. Lignitz S, Musholt TJ, Kreft A, Engel R, Brzezinska R, Pohlenz J. Intrathyroidal thymic tissue surrounding an intrathyroidal parathyroid gland, the cause of a solitary thyroid nodule in a 6-year-old boy. Thyroid 2008;18:1125-1130
  20. Durmaz E, Barsal E, Parlak M, Gurer I, Karaguzel G, Akcurin S, et al. Intrathyroidal ectopic thymic tissue may mimic thyroid cancer: a case report. J Pediatr Endocrinol Metab 2012;25:997-1000
  21. Chng CL, Kocjan G, Kurzawinski TR, Beale T. Intrathyroidal ectopic thymic tissue mimicking thyroid cancer in children. Endocr Pract 2014;20:e241-e245
  22. Park SH, Ryu CW, Kim GY, Shim KS. Intrathyroidal thymic tissue mimicking a malignant thyroid nodule in a 4-year-old child. Ultrasonography 2014;33:71-73
  23. Fukushima T, Suzuki S, Ohira T, Shimura H, Midorikawa S, Ohtsuru A, et al. Prevalence of ectopic intrathyroidal thymus in Japan: the Fukushima health management survey. Thyroid 2015;25:534-537
  24. Nishino M, Ashiku SK, Kocher ON, Thurer RL, Boiselle PM, Hatabu H. The thymus: a comprehensive review. Radiographics 2006;26:335-348
  25. Taub DD, Longo DL. Insights into thymic aging and regeneration. Immunol Rev 2005;205:72-93
  26. Nasseri F, Eftekhari F. Clinical and radiologic review of the normal and abnormal thymus: pearls and pitfalls. Radiographics 2010;30:413-428
  27. Kim HS, Han BK, Shin JH, Ko EY, Sung CO, Oh YL, et al. Papillary thyroid carcinoma of a diffuse sclerosing variant: ultrasonographic monitoring from a normal thyroid gland to mass formation. Korean J Radiol 2010;11:579-582