What is bronchogenic cyst

Bronchogenic cyst is a type of bronchopulmonary foregut malformation of the lung resulting from abnormal budding of the primitive foregut ¹ and are most commonly found in the mediastinum ². However, their location can be anywhere along the developmental pathway of the foregut in an ectopic site ³. Bronchogenic cysts include pulmonary sequestration, congenital cystic adenomatoid malformation, and congenital lobar hyperinflation (emphysema) ⁴.

Bronchogenic cysts are rare cystic lesions, with prevalences of 1 per 42,000 and 1 per 68,000 admissions in two hospital series ⁵. They are slightly more frequent in men and often remain undiscovered until the third or fourth decade of life ⁶. Bronchogenic cysts account for 10 to 15% of mediastinal tumors and 50 to 60% of all mediastinal cysts ⁷. Bronchogenic cysts originate preferentially in the middle mediastinum, including the right paratracheal area and the tracheal carina.

Classification of mediastinal bronchogenic cysts is in five types according to their location ⁸:

• Para-tracheal
• Carinal
• Para-esophageal
• Hilar
• Miscellaneous

Intrapulmonary bronchogenic cysts represent 20 to 30% and most commonly involve the lower lobes. They have no predilection for the right or left side.

The other locations of bronchogenic cysts are rare and include the pericardium, the pleura, the neck, the diaphragm, and the retroperitoneum.

In many instances, bronchogenic cysts are asymptomatic and are found incidentally when the chest is imaged ⁹. When large, mass effect may result in bronchial obstruction leading to air trapping and respiratory distress. An alternative presentation may occur when the cyst becomes infected. The treatment of all bronchogenic cysts has its basis as complete surgical excision, and their definitive diagnosis is established primarily by histopathological examination of the surgical specimen. Prognosis is excellent with no recurrences in case of complete resection.

Bronchogenic cyst causes

The cause of bronchogenic cysts is from the abnormal or late budding of the embryonic ventral lung bud or the tracheobronchial tree which occurs between the 26th and 40th days of gestation ¹⁰. This abnormal bud subsequently differentiates into a fluid-filled, blind-ending pouch ¹⁰. The location of bronchogenic cyst depends on the embryological stage of development at which the anomaly occurs. When the abnormal budding happens during early development, the cyst occupies the tracheobronchial tree. Bronchogenic cysts that arise later are more peripheral and may involve the lung parenchyma ¹¹.

Macroscopic findings of bronchogenic cysts ³:

• Spherical,
• Smooth,
• White or pinkish,
• Single or multiple,
• Size: from 2 to 12 cm in diameter,
• Frequently unilocular,
• Contain clear fluid, proteinaceous mucus, rarely air or hemorrhagic secretions,
• Calcification of the cyst wall is rare,
• They rarely communicate with the bronchial tree.

The definitive diagnosis of bronchogenic cysts derives histological examination of the surgical specimen.

Histological findings of bronchogenic cysts ³:

• Ciliated pseudostratified columnar epithelium of respiratory type
• Possible areas of squamous metaplasia
• Cyst wall contains airway components: cartilage plates, bronchial glands, and smooth muscle. Rarely: Nerve and adipose tissues ³.

Bronchogenic cyst symptoms

In pediatric patients: bronchogenic cysts may cause life-threatening compressive symptoms ¹².

In adults: bronchogenic cysts are often incidental radiologic findings ¹³. Pulmonary bronchogenic cysts are more likely to be symptomatic than mediastinal cysts, and 86.4% of symptomatic patients have a complicated cyst ¹⁴.

• Symptoms are secondary to cyst infection or compression of adjacent structures ¹⁵.
• Fistulized bronchogenic cysts cause cough, fever, sputum production, and hemoptysis.
• Non-fistulized bronchogenic cysts are usually responsible for chest pain ¹⁶.
• Pericystic pneumonitis or pneumonia in the adjacent compressed lung are responsible for fever and shortness of breath ¹⁷.

Bronchogenic cyst complications

According to some authors, bronchogenic cysts lead to complications in 45% of patients, but complications do not increase morbidity and death ¹⁸.

Complications of bronchogenic cysts include:

• Tracheobronchial compression and pulmonary infections,
• Rare complications comprise ¹⁴:
  • Pneumothorax
  • Fistula formation with the bronchial tree
  • Pleurisy
  • Superior vena cava syndrome
  • Stenosis of pulmonary artery
  • Arrhythmias
  • Ulceration of the cyst wall
  • Secondary bronchial atresia
  • Hemorrhage
  • Fatal air embolism in an airplane passenger
  • Malignant transformation is very rare (0.7% risk 11), but reported, with primaries including ⁹:
    • rhabdomyosarcoma
    • pleuropulmonary blastoma
    • anaplastic carcinoma
    • leiomyosarcoma
    • adenocarcinoma
  • Fatal myocardial infarction (heart attack) secondary to compression of the left main coronary artery.

Bronchogenic cyst diagnosis

Chest radiograph:

• Pulmonary bronchogenic cysts: Sharply defined, solitary, round or oval opacities, usually the lower lobe. They can present as a homogeneous water density, as an air-filled cyst, or with an air-fluid level. Abnormalities in the surrounding lung parenchyma, atelectasis or consolidation may occur and may make the diagnosis more difficult ¹⁹.
• Mediastinal bronchogenic cysts: Homogeneous, smooth, solitary, round or ovoid masses usually in the middle mediastinum ¹⁹.

Computed tomography scan:

It is the investigation of choice. The CT density of bronchogenic cysts is variable from typical water density to high density related to blood, increased calcium content, anthracotic pigment, or increased protein content of the fluid ¹⁹.

Magnetic resonance imaging (MRI):

Magnetic resonance imaging is better than CT scan at delineating anatomic relations and the definition of the cyst. The MRI appearance depends on the cyst’s content. On T1-weighted images, the intrinsic signal intensity varies from low to high, depending on the cyst contents. T2-weighted images show high signal intensity. Enhancement after contrast injection is frequently absent ¹⁹.

Bronchogenic cyst treatment

The choice of bronchogenic cyst treatment is somewhat controversial. The treatment of patients with bronchogenic cysts depends on symptoms at presentation and the patient’s age. Some authors advocate surgical excision of all bronchogenic cysts given their tendency to become infected or rarely, to undergo malignant transformation ⁹. Surgical resection alleviates symptoms, prevents complications and establishes the diagnosis of bronchogenic cysts. Symptomatic bronchogenic cysts should be resected (either by thoracotomy or via video-assisted thoracoscopy) regardless of patient age unless surgical risks are unacceptably high ¹⁰.

Increasingly, bronchogenic cysts are treated with thoracoscopic techniques such as transbronchial or percutaneous aspiration under CT guidance to both confirm the diagnosis and to treat bronchogenic cysts in adults. The benefits of thoracoscopy include decreased scarring, reduced pain, and shorter hospitalization. Complicated bronchogenic cysts usually require thoracotomy for more extensive resection ¹⁴. The resection must be complete because of the risk of recurrence after incomplete surgical removal. The treatment of asymptomatic bronchogenic cysts remains controversial. Most authors seem to advocate a surgical approach to prevent complications ¹³.

Small lesions can be followed, however they do have a tendency to increase in size over time, sometimes rapidly ²⁰.

Intrapulmonary bronchogenic cysts:

Lobectomy is the procedure of choice. However, in peripheral bronchogenic cysts or patients with limited lung function, a conservative procedure as a total pericystectomy, a wedge resection, or segmentectomy are recommended.

Mediastinal bronchogenic cysts:

The presence of adhesions especially in complicated forms of mediastinal bronchogenic cysts can lead to incomplete resection. Thus, resection or destruction of mucosa is a requirement to prevent accumulation of fluid and late recurrence ²¹.

An alternative option for bronchogenic cysts is close imaging surveillance to ensure temporal stability.

Bronchogenic cyst prognosis

The prognosis of bronchogenic cysts after surgical excision is excellent. In case of incomplete excision, late recurrences can occur ²². A recent study reviewing 102 patients treated for bronchogenic cysts, the estimated mean morbidity and mortality was 20% ²³.

References

1. Bronchogenic cysts: clinicopathological presentation and treatment. Aktoğu S, Yuncu G, Halilçolar H, Ermete S, Buduneli T. Eur Respir J. 1996 Oct; 9(10):2017-21.
2. Limaiem F, Mlika M. Bronchogenic Cyst. [Updated 2019 Jan 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536973
3. Limaïem F, Ayadi-Kaddour A, Djilani H, Kilani T, El Mezni F. Pulmonary and mediastinal bronchogenic cysts: a clinicopathologic study of 33 cases. Lung. 2008 Jan-Feb;186(1):55-61
4. Bronchogenic Cyst Imaging. https://emedicine.medscape.com/article/354447-overview
5. Limaïem F, Ayadi-Kaddour A, Djilani H, Kilani T, El Mezni F. Pulmonary and mediastinal bronchogenic cysts: a clinicopathologic study of 33 cases. Lung. 2008 Jan-Feb;186(1):55-61.
6. Lardinois D, Gugger M, Ris HB. Bronchogenic cyst of the left lower lobe associated with severe hemoptysis. Eur J Cardiothorac Surg. 1999 Sep;16(3):382-3
7. McAdams HP, Kirejczyk WM, Rosado-de-Christenson ML, Matsumoto S. Bronchogenic cyst: imaging features with clinical and histopathologic correlation. Radiology. 2000 Nov;217(2):441-6.
8. Mawatari T, Itoh T, Hachiro Y, Harada H, Kobayashi T, Saitoh T, Ohsawa H, Watanabe A, Abe T. Large bronchial cyst causing compression of the left atrium. Ann Thorac Cardiovasc Surg. 2003 Aug;9(4):261-3
9. Lucaya J, Baert AL, Strife JL. Pediatric Chest Imaging, Chest Imaging in Infants and Children. Springer Verlag. (2007) ISBN:3540326758
10. McAdams HP, Kirejczyk WM, Rosado-de-Christenson ML, Matsumoto S. Bronchogenic cyst: imaging features with clinical and histopathologic correlation. Radiology. 2000 Nov;217(2):441-6
11. St-Georges R, Deslauriers J, Duranceau A, Vaillancourt R, Deschamps C, Beauchamp G, Pagé A, Brisson J. Clinical spectrum of bronchogenic cysts of the mediastinum and lung in the adult. Ann. Thorac. Surg. 1991 Jul;52(1):6-13.
12. Cohn JE, Rethy K, Prasad R, Mae Pascasio J, Annunzio K, Zwillenberg S. Pediatric Bronchogenic Cysts: A Case Series of Six Patients Highlighting Diagnosis and Management. J Invest Surg. 2018 Nov 15;:1-6.
13. Bolton JW, Shahian DM. Asymptomatic bronchogenic cysts: what is the best management? Ann. Thorac. Surg. 1992 Jun;53(6):1134-7
14. Lee DH, Park CK, Kum DY, Kim JB, Hwang I. Clinical characteristics and management of intrathoracic bronchogenic cysts: a single center experience. Korean J Thorac Cardiovasc Surg. 2011 Aug;44(4):279-84
15. Patel SR, Meeker DP, Biscotti CV, Kirby TJ, Rice TW. Presentation and management of bronchogenic cysts in the adult. Chest. 1994 Jul;106(1):79-85
16. Ribet ME, Copin MC, Gosselin B. Bronchogenic cysts of the mediastinum. J. Thorac. Cardiovasc. Surg. 1995 May;109(5):1003-10
17. St-Georges R, Deslauriers J, Duranceau A, Vaillancourt R, Deschamps C, Beauchamp G, Pagé A, Brisson J. Clinical spectrum of bronchogenic cysts of the mediastinum and lung in the adult. Ann. Thorac. Surg. 1991 Jul;52(1):6-13
18. Rice DC, Putnam JB. Recurrent bronchogenic cyst causing recurrent laryngeal nerve palsy. Eur J Cardiothorac Surg. 2002 Mar;21(3):561-3
19. Chen TJ, Liao CH, Shen TC. Bronchogenic cyst. QJM. 2018 Dec 01;111(12):905
20. Naidich DP, Srichai MB, Krinsky GA. Computed tomography and magnetic resonance of the thorax. Lippincott Williams & Wilkins. (2007) ISBN:0781757657
21. Hasegawa T, Murayama F, Endo S, Sohara Y. Recurrent bronchogenic cyst 15 years after incomplete excision. Interact Cardiovasc Thorac Surg. 2003 Dec;2(4):685-7
22. Gharagozloo F, Dausmann MJ, McReynolds SD, Sanderson DR, Helmers RA. Recurrent bronchogenic pseudocyst 24 years after incomplete excision. Report of a case. Chest. 1995 Sep;108(3):880-3
23. Makhija Z, Moir CR, Allen MS, Cassivi SD, Deschamps C, Nichols FC, Wigle DA, Shen KR. Surgical management of congenital cystic lung malformations in older patients. Ann. Thorac. Surg. 2011 May;91(5):1568-73; discussion 1573