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Thymic Cyst

Definition

  • Epithelial lined cyst involving the thymus

Diagnostic Criteria

  • Frequently separated into congenital and aquired types
    • Common features
      • May occur at all ages
      • May be found in neck or mediastinum
      • Thymic tissue must be present at least focally within the wall of the cyst
    • Congenital type
      • Thin wall
      • May be unilocular or multilocular
      • Lined by squamous, glandular or ciliated epithelium
    • Acquired type
      • Walls thickened by inflammatory infiltrate
        • May have germinal centers
      • Virtually alwalys multilocular
      • Lined by squamous or columnar epithelium
        • May exhibit pseudoepitheliomatous hyperplasia
      • Frequent cholesterol clefts and granulomas
      • One report of four patients with associated fever and autoimmune disease (Izumi)
        • Cured by resection
      • May be associated with any neoplasm, but most frequently with:
  • Both types are benign (if not associated with a neoplasm)

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

Original posting/updates: 9/24/10

Differential Diagnosis

  • Thymic cysts, both primary and acquired are distinguished from other types of cysts by the identification of thymic tissue in their walls
    • Cervical
      • Branchial cleft
      • Cervial bronchial
      • Thyroglossal
    • Mediastinal
      • Bronchal
      • Esophageal duplication
      • Lymphangioma
      • Pericardial
  • Associated neoplasm must be ruled out in all cases

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
  • den Bakker MA, Oosterhuis JW. Tumours and tumour-like conditions of the thymus other than thymoma; a practical approach. Histopathology. 2009 Jan;54(1):69-89
  • Moran CA, Suster S. Cystic well-differentiated neuroendocrine carcinoma (carcinoid tumor): a clinicopathologic and immunohistochemical study of two cases. Am J Clin Pathol. 2006 Sep;126(3):377-80
  • Izumi H, Nobukawa B, Takahashi K, Kumasaka T, Miyamoto H, Yamazaki A, Sonobe S, Uekusa T, Suda K. Multilocular thymic cyst associated with follicular hyperplasia: clinicopathologic study of 4 resected cases. Hum Pathol. 2005 Jul;36(7):841-4
  • Kuroki S, Nasu K, Murakami K, Hayashi T, Sekiguchi R, Nishida H, Miyagawa K, Kuroki Y, Nawano S. Thymic MALT lymphoma: MR imaging findings and their correlation with histopathological findings on four cases. Clin Imaging. 2004 Jul-Aug;28(4):274-7
  • Suster S, Rosai J. Cystic thymomas. A clinicopathologic study of ten cases. Cancer. 1992 Jan 1;69(1):92-7
  • Suster S, Barbuto D, Carlson G, Rosai J. Multilocular thymic cysts with pseudoepitheliomatous hyperplasia. Hum Pathol. 1991 May;22(5):455-60
  • Suster S, Rosai J. Multilocular thymic cyst: an acquired reactive process. Study of 18 cases. Am J Surg Pathol. 1991 Apr;15(4):388-98.
  • Salyer DC, Salyer WR, Eggleston JC. Benign developmental cysts of the mediastinum. Arch Pathol Lab Med. 1977 Mar;101(3):136-9
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