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Surgical Pathology Criteria
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Thymic Dysplasia

Definition

  • Congenital architectural changes of the thymus associated with immunodeficiency

Alternate/Historical Names

  • Thymic aplasia
  • Thymic hypoplasia

Diagnostic Criteria

  • Lack of lobular architecture
    • Even involuted normal thymus retains lobular pattern
  • Lack of defined cortical and medullary zones
    • Even involuted cortex is usually distinguishable from medulla
    • Hassal corpuscles usually absent
  • Few or no lymphocytes
    • May also be lacking in involution
  • No precise correlation of pattern with clinical syndrome
  • Thymus in Down syndrome retains lobularity and Hassal corpuscles
  • Thymic aplasia refers to absence of any formed thymus
    • Seen in DiGeorge syndrome

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/updates: 9/24/10

Classification / Lists

Miscellaneous Thymic Lesions and Conditions

Bibliography

  • Shimosato Y, Mukai K, Matsuno Y. Tumors of the Mediastinum, Atlas of Tumor Pathology, AFIP Fourth Series, Fascicle 11, 2010
  • Nezelof C. Thymic pathology in primary and secondary immunodeficiencies. Histopathology. 1992 Dec;21(6):499-511
  • Larocca LM, Lauriola L, Ranelletti FO, Piantelli M, Maggiano N, Ricci R, Capelli A. Morphological and immunohistochemical study of Down syndrome thymus. Am J Med Genet Suppl. 1990;7:225-30
  • van Baarlen J, Schuurman HJ, Huber J. Acute thymus involution in infancy and childhood: a reliable marker for duration of acute illness. Hum Pathol. 1988 Oct;19(10):1155-60
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