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Thymic cyst

Dr Frank Gaillard et al.

Thymic cyst is a cyst that occurs in relation to the thymus.

They can be seen in a variety of settings:

  • congenital: contains thymic tissue in wall, often unilocular
  • acquired: often multi locular
    • secondary to thoracotomy
    • following chemotherapy or radiotherapy for mediastinal malignancy
    • inflammatory


They are uncommon lesions and are estimated to account for approximately 3% of all anterior mediastinal masses 4.


The presence of Hassall's corpuscles in the cyst wall is diagnostic especially in congenital lesions. The cysts often contain turbid fluid or gelatinous material.


Can be broadly divided into:

Larger lesions can sometimes occur in combination.

Radiographic features


Typically manifest as unilocular or multilocular cystic masses with well-defined walls. Lesions can be lobulated and may have soft-tissue attenuation components.


Signal characteristics are similar to any simple cyst and are:

  • T1: low signal
  • T2: high signal 
  • T1 C+ (Gd): no intrinsic enhancement

Differential diagnosis

If cervical consider
If mediastinal consider

See also

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