multilocular thymic cyst

Definition: Multilocular thymic cyst (MTC) most likely results from the cystic transformation of medullary duct epithelium-derived structures (including Hassall corpuscles) induced by an acquired inflammatory process. (2006719)

Multilocular thymic cyst (MTC) would be pathogenetically analogous to a variety of cystic conditions of the head and neck region, for which the common denominator seems to be the induction of cystic transformation in ductular epithelial formations of branchial pouch or related derivation by an acquired inflammatory process. (2006719)

See also : proliferating multilocular thymic cyst

Synopsis (2006719)

 thick-walled multiloculated cavities filled with turbid yellow fluid
 multiple cystic cavities partially lined by squamous, columnar, or cuboidal epithelium (some having features of Hassall corpuscles)
 scattered nests and islands of non-neoplastic thymic tissue within the cyst walls, often continuous with the cyst lining
 severe acute and chronic inflammation
 fibrovascular proliferation
 necrosis
 hemorrhage
 cholesterol granuloma formation (cholesterol cleft granulomas)
 reactive lymphoid hyperplasia with prominent germinal centers
 rarely, pseudoepitheliomatous hyperplasia (1709608)

Associations

 thymoma
 anterior mediastinal yolk sac tumors (9267822)
 Sjögren syndrome (11603465)
 thymic Hodgkin disease
 thymic seminoma
 thymic carcinoma

Complications

 squamous cell carcinomas (SCC) arising in multilocular thymic cysts of the neck (14717671)

Physiopathology

MTC most likely results from the cystic transformation of medullary duct epithelium-derived structures (including Hassall’s corpuscles) induced by an acquired inflammatory process.

The changes are similar to those sometimes seen in association with thymic Hodgkin’s disease and thymic seminoma, which are also probably due to the inflammation that accompanies these tumors rather than to the tumors themselves.

MTC is pathogenetically analogous to a variety of cystic conditions of the head and neck region, for which the common denominator seems to be the induction of cystic transformation in ductular epithelial formations of branchial pouch or related derivation by an acquired inflammatory process.

References

 Suster S, Barbuto D, Carlson G, Rosai J. Multilocular thymic cysts with pseudoepitheliomatous hyperplasia. Hum Pathol. 1991 May;22(5):455-60. PMID: 1709608

 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. PMID: 2006719