Differentiation of Remnant or Hyperplastic Thymus Tissue from Thymus Malignancies

Öz

The thymus is encountered on all cross-sectional imaging studies of the chest, unless ectopic or surgically absent. Thymus has a variable appearance, undergoes dynamic changes during periods of stress and ages, and demonstrates numerous different lesions. Understanding the radiologic features of normal variants and benign conditions can help prevent unnecessary imaging and intervention. In this article, normal thymic anatomy and its development, remnant thymic tissue and thymic hyperplasia will be reviewed. In addition, radiological images that will distinguish it from other malign pathologies of the thymus will be reviewed.

Anahtar Kelimeler

• Remnant thymus,hyperplastic thymus,differantiation from malignancies

Kalıntı veya Hiperplazik Timus Dokusunun Timus Malignitelerinden Ayırımı

Öz

Timus, ektopik olmadığı veya cerrahi olarak çıkartılmadığı sürece göğsün tüm kesitsel görüntüleme çalışmalarında görülür. Timus değişken bir görünüme sahiptir, yaş ve stres dönemlerinde dinamik değişikliklere uğrar ve çok sayıda farklı lezyon gösterir. Normal varyantların ve benign durumların radyolojik özelliklerini bilmek, gereksiz görüntüleme ve müdahalelerin önlenmesine yardımcı olabilir. Bu makalede normal timik anatomi ve gelişimi, kalıntı timik doku ve timik hiperplazi gözden geçirilecektir. Ayrıca bunların, timusun malign patolojilerinden ayıracak radyolojik görüntüleri gözden geçirilecektir.

Anahtar Kelimeler

• Kalıntı timus,hiperplazik timus,malignitelerden ayırım

Kaynakça

1. 1. Jacobs MT, Frush DP, Donnelly LF. The right place at the wrong time: historical perspective of the relation of the thymus gland and pediatric radiology. Radiology 1999;210:11-16.
2. 2. Shimosato Y, Mukai K. Tumors of the thymus and related lesions. In: Shimosato Y, Mukai K, eds. Atlas of tumor pathology: tumors of the medi- astinum, fasc 21, ser 3. Washington, DC: Armed Forces Institute of Pathology, 1997.
3. 3. Nasseri F, Eftekhari E. Clinical and radiologic review of the normal and abnormal thymus: pearls and pitfalls. RadioGraphics 2010;30:413-28.
4. 4. Ge Q, Zhao Y. Evolution of thymus organogenesis. Dev Comp Immunol 2013;39:85-90.
5. 5. Rezzani R, Nardo L, Favero G, et al. Thymus and aging: Morphological, radiological, and functional overview. Age (Omaha) 2014;36:313-351.
6. 6. Masaoka A, Extended transsternal Tymectomy. In: Shields TW, Locicero J,Ponn RB, Rusch VW. Ed. General Thoracic Surgery. Sixth edition. Philadelphia: Williams&Wilkins, 2005.
7. 7. Fukai I, Funato Y, Mizuno T, et al. Distrubition of tymic tissue in the mediastinal adipose tissue. J Thorac Cardiovasc Surg 1988;96:711-6.
8. 8. Weis CA, Markl B, Schuster T, et al. “Echte Thymushyperplasie” Differenzial diagnose der thymus vergroserung bei auglingen und Kindern. Pathologe. 2017;38:286-293.

9. 9. Parker LA, Gaisie G, Scatliff JH. Computerized tomography and ultrasonographic findings in massive thymic hyperplasia. Case discussion and review of current concepts. Clin Pediatr (Phila). 1985;24:90-94.
10. 10. Yan F, Mo X, Liu J, et al. Thymic function in the regulation of T cells, and molecular mechanisms underlying the modulation of cytokines and stress signaling (Review). Mol Med Rep 2017;16:7175-7184.
11. 11. Sklair-Levy M, Agid R, Sella T, et al. Age- related changes in CT attenuation of the thymus in children. Pediatr Radiol 2000;30:566-569.
12. 12. Siegel MJ. Pediatric body CT. Philadelphia, Pa: Lippincott Williams & Wilkins, 2008.
13. 13. Shahrzad M, Mai Le Ts, Silva M, et al. Anterior Mediastinal Masses AJR 2014;203:128-138.
14. 14. Kuo T. Cytokeratin profiles of the thymus and thymomas: histogenetic correlations and proposal for a histological classification of thymomas. Histopathology 2000;36:403-14.
15. 15. Francis IR, Glazer GM, Bookstein FL, et al. The Thymus: reexamination of age-related changes in size and shape. AJR 1985;145:249-54.
16. 16. Akkus M. Mediyasten tümörleri ve cerrahi yaklaşım. In: Eren Ş, Esme H. (eds.) Torasik Cerrahi. S 521-540. 1. Baskı. İstanbul Medikal Yayıncılık, İstanbul, 2019.
17. 17. Moon SH, Kim HS, Cho YS, et al. Value of volume-based early metabolic response in patients withunresectable thymic epithelial tumor. Lung Cancer 2016;100:24-29.
18. 18. Fukumoto K, Fukui T, Okasaka T, et al. The Role of 18F-fluorodeoxyglucose positron emission tomography-computed tomography for predicting pathologic response after induction therapy for thymic epithelial tumors. World J Surg 2017;41:1828-1833.
19. 19. Chen CH, Hsiao CC, Chen YC, et al. Rebound thymic hyperplasia after chemotherapy in children with lymphoma. Pediatrics and Neonatology 2017;58:151-157.
20. 20. Priola AM, Priola SM. Chemical-shift MRI of rebound thymic hyperplasia with unusual appearance and intense 18F-FDG uptake in adulthood: report of two cases. Clin Imaging 2014;38:739-744.
21. 21. Godart V, Weynand B, Coche E, et al. Intense 18-fluorodeoxyglucose uptake by the thymus on PET scan does not necessarily herald recurrence ofthyroid carcinoma. J Endocrinol Invest 2005;28:1024-1028.