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Thymic Cyst

A thymic cyst is an epithelium lined cyst involving the thymus. These cysts are often separated into congenital or acquired types. Congenital cysts are thin-walled, having thymic tissue in their lining and acquired cysts are multilocular and are usually formed as a result of an inflammatory process.


Presentation

Most mediastinal cysts, including thymic cysts, are asymptomatic and incidentally found after chest imaging for other reasons. Approximately half of individuals with thymomas and thymic cysts are clinically asymptomatic. Symptoms are more commonly observed in infants and children, in which the cyst enlarges and compresses structures producing related symptoms [1]. For example, a thymic cyst may enlarge to compress the trachea resulting in dyspnea. Adults may present with non-specific chest pain, cough, stridor, and/or dyspnea [2].

Pseudotumor
  • BACKGROUND: Multilocular thymic cyst with follicular lymphoid hyperplasia is a rare complication in HIV-infected patients, causing pseudotumorous enlargement of the anterior mediastinum.[ncbi.nlm.nih.gov]
Intermittent Fever
  • Three patients presented high-grade intermittent fever, and 2 patients were associated with Sjogren syndrome with elevated serum antinuclear antibody levels. All patients were subjected to extended thymectomy.[ncbi.nlm.nih.gov]
Confusion
  • Our aim is to highlight the possibility of confusing between benign and malignant thymus cysts having different cure approach. We report two thymic cyst cases, one congenital ectopic condition, and the other one, a cystic thymoma.[ncbi.nlm.nih.gov]
  • This can lead to potential confusion amongst clinicians on how to best treat these patients. We report the successful diagnosis and treatment of a 76 year-old female with a giant, benign thymic cyst.[ncbi.nlm.nih.gov]

Workup

Workup consists of ensuring the proper diagnosis of a thymic cyst and ruling out associated benign and malignant conditions such as: cystic teratoma, lymphangioma, cystic degeneration of a seminoma, pericardial cyst, thymoma, and thymic cancer [3]. Workup begins with patient history, physical exam, and imaging tests. The most common imaging modality currently used to evaluate a mediastinal mass is a chest computed tomography (CT) scan. Other imaging modalities used include magnetic resonance imaging and integrated positron emission tomography and CT (PET/CT) scan. A definitive diagnosis is established by pathological tissue examination (via biopsy or surgical resection).

On standard chest radiographs, thymic cysts may not be visible or may be indistinguishable from other non-lobulated thymic masses [4]. Further workup should include a chest computed tomography (CT) scan and biopsy if clinically indicated. On CT scan, congenital thymic cysts usually appear as well-defined water-attenuated masses with translucent walls. Multilobular thymic cysts appear as well-defined, heterogeneous, cystic masses with a visible wall [5] [6]. Some thymic cysts, in particular acquired cysts, may have an increased CT attenuation if infection or hemorrhage is present; these cysts may be erroneously diagnosed as solid masses. In some cases, there may be curvilinear calcification of the cyst wall [7].

Magnetic resonance imaging (MRI) depicts thymic cysts having typical characteristics of fluid (e.g., low signal intensity on T1-weighted images and uniform high signal intensity on T2-weighted images). If hemorrhage or infection is present, the cysts will show high signal intensity on both T1- and T2-weighted images. In summary, uncomplicated thymic cysts have the following characteristics on MRI [8]:

  • T1-weighted images - low signal
  • T2-weighted images - high signal
  • T1 C+ (Gd) images: no intrinsic enhancement
  • If hemorrhage or infection occurs, then there will be high signal intensity on both T1 and T2-weighted images.

A PET/CT scan provides a CT image as well as information about the avidity of the lesion for glucose (FDG uptake). Malignant cells tend to have higher glucose avidity, hence producing a high uptake value on the PET/CT scan. This information can provide clues about whether a thymic lesion is a benign cyst or malignant entity [9].

Definitive diagnosis is achieved by obtaining tissue for pathologic examination by way of either a surgical biopsy or surgical resection. Most surgical resections are performed using minimally invasive surgical technique called video-assisted thoracoscopy (VATS). VATS biopsy requires the patient to be placed under general anesthesia in the operating room. More recently, robotic surgical approach has been used to evaluate and resect mediastinal masses (including thymic cysts) [10].

Treatment

  • Surgical resection is the treatment of choice for definitive diagnosis, resolution of symptoms and cure.[ncbi.nlm.nih.gov]
  • Because of the possible coexistence of typical congenital thymic cyst and thymoma, we recommend surgical resection both for establishing the diagnosis and for definite treatment.[ncbi.nlm.nih.gov]
  • The etiologic theories, differential diagnosis and the treatment of thymic cysts are discussed.[ncbi.nlm.nih.gov]
  • This therapy may be one of the best treatments for thymic cysts, especially in very elderly patients.[ncbi.nlm.nih.gov]
  • Treatment consisted of dual-chamber pacemaker implantation prior to video-assisted removal of the thymic cyst.[ncbi.nlm.nih.gov]

Prognosis

  • Surgery is the treatment of choice and prognosis is excellent if the lesion is completely removed.[revistas.rcaap.pt]
  • Talk to your doctor to get more accurate information about your prognosis.[healthline.com]

Etiology

  • The etiologic theories, differential diagnosis and the treatment of thymic cysts are discussed.[ncbi.nlm.nih.gov]
  • Delay in recognizing the underlying etiology can lead to significant complications.[ncbi.nlm.nih.gov]
  • […] abundant epithelioid granulomata within the cyst, a finding that has not previously been emphasized as a histologic feature of these lesions, and one that expands the histopathologic differential diagnosis, warranting exclusion of infectious and autoimmune etiologies[ncbi.nlm.nih.gov]
  • Inflammation in Thymic Cysts is idiopathic, although in some cases a specific etiology (HIV infection, Autoimmune Disorder) is to be ruled out.[jemds.com]

Epidemiology

  • […] pouch, as is parathyroid gland Usually presents as incidental mass in anterosuperior mediastinum Congenital (unilocular) or acquired (multilocular) Rarely occur postoperatively Mixed multilocular thymic cyst: has parathyroid or salivary gland tissue Epidemiology[pathologyoutlines.com]
Sex distribution
Age distribution

Prevention

  • These type of tumors cannot be prevented. Mediastinal Tumor Menu The mediastinum is divided into three sections What are mediastinal tumors? Tumors (also called neoplasms) are masses of cells. They can be benign (not cancer) or malignant (cancer).[my.clevelandclinic.org]
  • Grossly, they had a spongy appearance with typical microscopy. [19] Surgical intervention is the preferred line of management of all mediastinal cysts, regardless of size and clinical presentation, so as to prevent development of various complications[jpgmonline.com]

References

Article

  1. Hamaji M, Ali SO, Burt BM. A meta-analysis of surgical versus nonsurgical management of recurrent thymoma. Ann Thorac Surg. 2014; 98:748-55.
  2. Rieger R, Schrenk P, Woisetschlager R, Wayand W. Videothoracoscopy for the management of mediastinal mass lesions. Surg Endosc. 1996;10:715-7.
  3. Suster S1, Rosai J. Multilocular thymic cyst: an acquired reactive process. Study of 18 cases. Am J Surg Pathol. 1991;15:388-98.
  4. Jeung MY, Gasser B, Gangi A, et al. Imaging of cystic masses of the mediastinum. Radiographics: a review publication of the Radiological Society of North America, Inc. 2002; 22:S79-93.
  5. Choi YW, McAdams HP, Jeon SC, et al. Idiopathic multilocular thymic cyst: CT features with clinical and histopathologic correlation. Am J Roentgenol 2001; 177:881-885.
  6. Brown LR, Aughenbaugh GL. Masses of the anterior mediastinum: CT and MRI findings. AJR Am J Roentgenol 1991; 157:1171-80.
  7. Strollo DC, Rosado-de-Christenson ML, Jett JR. Primary mediastinal tumors. Part 1. Tumors of the anterior mediastinum. Chest 1997; 112:511-22.
  8. Zhang M, Endo M, Adachi S, et-al. Multilocular thymic cyst: MR findings. AJR Am J Roentgenol. 1994;163:479-80.
  9. McErlean A, Huang J, Zabor EC, Moskowitz CS, Ginsberg MS. Distinguishing benign thymic lesions from early-stage thymic malignancies on computed tomography. Journal of thoracic oncology: official publication of the International Association for the Study of Lung Cancer. 2013; 8: 967-73.
  10. Rieger R, Schrenk P, Woisetschlager R, Wayand W. Videothoracoscopy for the management of mediastinal mass lesions. Surg Endosc. 1996;10:715-7.

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Last updated: 2017-08-09 17:38