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
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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.
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
If cervical consider
- branchial cleft cyst: any type dependant on location
If mediastinal consider
- 1. Brown LR, Aughenbaugh GL. Masses of the anterior mediastinum: CT and MR imaging. AJR Am J Roentgenol. 1991;157 (6): 1171-80. AJR Am J Roentgenol (abstract) - Pubmed citation
- 2. Moskowitz PS, Noon MA, Mcalister WH et-al. Thymic cyst hemorrhage: a cause of acute, symptomatic mediastinal widening in children with aplastic anemia. AJR Am J Roentgenol. 1980;134 (4): 832-6. AJR Am J Roentgenol (citation) - Pubmed citation
- 3. Zhang M, Endo M, Adachi S et-al. Multilocular thymic cyst: MR findings. AJR Am J Roentgenol. 1994;163 (2): 479-80. AJR Am J Roentgenol (citation) - Pubmed citation
- 4. Choi YW, Mcadams HP, Jeon SC et-al. Idiopathic multilocular thymic cyst: CT features with clinical and histopathologic correlation. AJR Am J Roentgenol. 2001;177 (4): 881-5. AJR Am J Roentgenol (full text) - Pubmed citation