Bronchogenic Cyst

Etiology

Bronchogenic cysts are congenital malformations that arise from abnormal budding or diverticulation of the primitive foregut, typically between the third and seventh weeks (days 26 to 40) of gestation.[5] This early developmental error leads to the formation of fluid-filled, blind-ending pouches that originate along the tracheobronchial tree, resulting in diverse presentation sites due to the origin of the foregut endodermal tissue.[5] These cysts most commonly appear in the mediastinum or lung parenchyma, though they can also be found in rarer, ectopic sites such as the neck, retroperitoneum, diaphragm, or subcutaneous tissues. The specific timing of abnormal budding influences the cyst’s eventual location: if the error occurs early in gestation, cysts are more likely to form centrally in the tracheobronchial tree or mediastinum, including the right paratracheal area and tracheal carina, which are preferred sites. Abnormal budding later in development tends to result in peripheral cysts within the lung parenchyma, often in the lower lobes, with no side preference. Approximately 20% to 30% of bronchogenic cysts fall into this intrapulmonary category.[6][7]

Bronchogenic cysts account for 10% to 15% of mediastinal tumors and 50% to 60% of mediastinal cysts, predominantly in the middle mediastinum. They are classified into 5 types based on location: paratracheal, carinal, paraesophageal, hilar, and miscellaneous.[8] Most bronchogenic cysts are lined with respiratory epithelium and may contain cartilage, smooth muscle, and mucus-secreting glands, reflecting their respiratory origin. The exact cause of abnormal budding remains unclear; disruptions in signaling pathways essential for respiratory tract development—such as sonic hedgehog, fibroblast growth factors, and bone morphogenetic proteins—are thought to play a role. Errors in these pathways during critical developmental periods may contribute to cyst formation.

While many bronchogenic cysts remain asymptomatic, others can lead to complications if they enlarge, become infected, or fistulize to adjacent organs, potentially causing symptoms such as airway obstruction, recurrent infections, or chest discomfort. Rarely, fistulization can result in severe complications like air embolism, and there have been sporadic reports of malignant transformation, emphasizing the need for monitoring. Additionally, bronchogenic cysts have been occasionally associated with other congenital anomalies, suggesting a possible genetic or multifactorial basis for their etiology.

Epidemiology

Bronchogenic cysts are rare congenital malformations, with an estimated prevalence of 1 in 42,000 to 1 in 68,000 individuals based on surgical and autopsy series study results.[2] They account for 10% to 15% of mediastinal tumors and 50% to 60% of all mediastinal cysts.[5] These cysts are most commonly diagnosed in children or young adults, although some cases remain undiscovered until the third or fourth decade of life.[9][10] Most bronchogenic cysts are detected in the first few years of life, often due to respiratory symptoms resulting from cyst enlargement or infection. In asymptomatic cases, cysts may remain undiagnosed until later in adulthood, particularly if imaging is obtained for unrelated reasons.

The incidence and presentation of bronchogenic cysts vary by anatomical location, patient sex, and clinical manifestations, though they appear equally across different ethnic and geographic populations without racial predilection. The cysts originate preferentially in the middle mediastinum, including the right paratracheal area and the tracheal carina. Mediastinal bronchogenic cysts are the most common, comprising about 50% to 70% of cases, and are frequently found in the middle and posterior mediastinum. Bronchogenic cysts affect males and females equally and typically present earlier due to their proximity to the tracheobronchial tree, where they may compress surrounding structures, causing respiratory symptoms. Intrapulmonary cysts, accounting for around 20% to 30% of cases, are more common in males. Although initially asymptomatic, these cysts may later lead to complications such as recurrent infections or, in rare instances, pneumothorax if they rupture. Gastric bronchogenic cysts, a rare ectopic subtype, have a female predominance with a female-to-male ratio of approximately 21:14.[11] Bronchogenic cysts are generally considered sporadic but are occasionally associated with other congenital anomalies, including esophageal duplication cysts and cardiac malformations. Such associations suggest bronchogenic cysts may be part of a broader spectrum of foregut-derived anomalies in some instances, possibly influenced by genetic or environmental factors during development.

Histopathology

The gross and histopathological findings of bronchogenic cysts provide essential insights into their nature as congenital malformations. Macroscopically, bronchogenic cysts typically present as spherical, smooth lesions that may vary from white to pinkish. These cysts can be single or multiple, with diameters ranging from 2 to 12 cm. Most often, they are unilocular and contain clear fluid or proteinaceous mucus, although air or hemorrhagic secretions can be found in rare cases. Calcification of the cyst wall is uncommon, and they rarely communicate with the bronchial tree.[2] The definitive diagnosis of bronchogenic cysts relies on histological examination of the surgical specimen.

Histologically, bronchogenic cysts are characterized by a lining of ciliated pseudostratified columnar epithelium of respiratory type, with possible areas of squamous metaplasia.[2] The cyst wall may contain various airway components, including cartilage plates, bronchial glands, and smooth muscle. Rarely are nerve and adipose tissues observed within the cyst wall.[2] Bronchogenic cysts can exhibit histological alterations due to infarction, infection, or previous medical interventions. These changes may manifest as acute or chronic inflammation, epithelial denudation, and bleeding, leading to hemosiderin-laden macrophages, cholesterol clefts, and fibrosis. The combination of these macroscopic and histopathological features reflects the complex nature of bronchogenic cysts, emphasizing their developmental origin and potential for complications. Recognition of these characteristics is crucial for accurate diagnosis and management in clinical practice.

History and Physical

Given the diverse clinical presentations of these congenital malformations across different age groups, the history and physical examination of patients with bronchogenic cysts can vary significantly. In pediatrics, bronchogenic cysts may cause life-threatening compressive symptoms.[12] Diagnosis often occurs when the cysts become infected or enlarge enough to compress surrounding structures.[13][14] In adults, bronchogenic cysts are often incidental radiologic findings.[15] Pulmonary bronchogenic cysts are more likely to be symptomatic than mediastinal cysts, and 86.4% of symptomatic patients have a complicated cyst.[16]

Medical History

Asymptomatic presentation: Many patients with bronchogenic cysts are asymptomatic, and they are often discovered incidentally during imaging studies for unrelated issues. This is particularly common for cysts in the lung parenchyma or those that do not exert pressure on adjacent structures.

Respiratory symptoms: Patients who present with symptoms may report a range of respiratory issues, including cough, dyspnea, and chest pain. The cough may be chronic and nonproductive, especially if the cyst has become infected or increased in size. Patients may experience shortness of breath due to airway compression, particularly with mediastinal cysts. In children, bronchogenic cysts may cause life-threatening compressive symptoms, leading to severe respiratory distress. While nonfistulized bronchogenic cysts typically cause chest pain due to pressure on surrounding structures, fistulized cysts can result in additional symptoms, such as cough, fever, sputum production, and hemoptysis.[17]

Infection history: Many symptomatic individuals with bronchogenic cysts have recurrent respiratory infections, indicating potential complications such as cyst infection or inflammation. Fever and shortness of breath may occur due to pericystic pneumonitis or pneumonia in the adjacent compressed lung.[6] Patients with active infection may report malaise.

Past medical history: Patients may have a history of respiratory issues or congenital anomalies. The presence of other congenital malformations, particularly cardiac defects or other foregut anomalies, can be associated with bronchogenic cysts.

Developmental history: In children with a bronchogenic cyst, obtaining a developmental history may reveal relevant congenital conditions.

Physical Examination

General appearance: If asymptomatic, patients may appear well-nourished and in no acute distress. Symptomatic individuals, especially children, may exhibit signs of respiratory distress or systemic infection.

Respiratory examination: Auscultation may be normal in asymptomatic individuals. However, in symptomatic individuals, decreased breath sounds may be noted on the affected side, particularly with large cysts. Abnormal sounds like wheezing or crackles can occur if there is an associated infection or atelectasis. Percussion may reveal dullness over areas of consolidation or if a cyst is large enough to affect normal lung inflation.

Vital signs: Patients who are asymptomatic may present with normal vital signs. However, those with significant respiratory involvement may be tachypneic, hypoxic, or tachycardic, especially during exacerbations or infections; patients with active infections may be febrile.

Neck and mediastinal assessment: In situations where bronchogenic cysts are located in ectopic sites, such as the neck or retroperitoneum, a mass may be palpable. Mediastinal cysts might also cause tracheal deviation or other signs of mediastinal shift.

Evaluation

Evaluating a patient with a suspected bronchogenic cyst involves a combination of laboratory tests, imaging studies, and occasionally more specialized procedures. These investigations help confirm the diagnosis, assess the cyst’s characteristics, and rule out complications.

Laboratory Tests

Complete blood count: This test may reveal leukocytosis in patients with active infection or anemia in those with chronic disease.

C-reactive protein: An elevated serum C-reactive protein may indicate inflammation or infection associated with the cyst.

Sputum cultures: Respiratory symptoms such as cough, sputum production, or hemoptysis may warrant obtaining sputum cultures, which can help identify infectious agents if the cyst is infected.

Blood cultures: Patients with systemic signs consistent with bacteremia, such as fever or chills, may warrant blood cultures.

Radiographic Imaging

Chest radiography: A chest x-ray is often the first imaging study performed when bronchogenic cysts are suspected. Pulmonary bronchogenic cysts will be sharply defined, solitary, round, or oval opacities, usually the lower lobe appearing as a homogeneous water density, an air-filled cyst, or with an air-fluid level. Abnormalities in the surrounding lung parenchyma, like atelectasis or consolidation, may make the diagnosis more difficult.[18] Mediastinal bronchogenic cysts appear as homogeneous, smooth, solitary, round, or ovoid masses, usually in the middle mediastinum.[5][18]

Computed tomography: Computed tomography (CT) is the investigation of choice, providing detailed imaging of the cyst’s location, size, position, and relationship to tracheobronchial and vascular structures.[19] CT is beneficial in evaluating cysts located within the lungs or at ectopic sites. This study can help differentiate bronchogenic cysts from other mediastinal masses. The CT density of bronchogenic cysts varies from typical water density to high density related to blood, increased calcium content, anthracotic pigment, or increased protein content of the fluid.[5][18] CT can also assess the presence of associated complications, such as infection, surrounding inflammatory changes, or airway compression. In some cases, a contrast-enhanced CT scan may be performed to delineate the vascular structures better and assess for any associated complications, such as vascular involvement or other tumors.

Magnetic resonance imaging: Magnetic resonance imaging (MRI) is not always required when evaluating a patient with a suspected bronchogenic cyst. Still, it is especially useful when evaluating complex cysts or when better soft tissue contrast is needed. MRI is superior to CT for delineating anatomic relations and the definition of the cyst. The MRI appearance of the cyst is dictated by its 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.[5][18]

Ultrasonography: Although less commonly employed when diagnosing bronchogenic cysts, ultrasonography may help evaluate cysts in atypical locations, such as the neck or retroperitoneum, particularly in pediatric patients.

Other Required Tests

Bronchoscopy: This allows direct visualization of the bronchial tree and can be useful if bronchogenic cysts are suspected of causing airway obstruction. This study can also facilitate sampling for cultures or biopsies if necessary.

Endoscopic ultrasonography: Cysts located in the mediastinum or retroperitoneum can be further evaluated by endoscopic ultrasonography, providing real-time imaging and allowing for fine-needle aspiration. 

Histopathological examination: This remains the gold standard for definitively diagnosing bronchogenic cysts by examining tissue obtained via surgical excision or biopsy.[20] This examination can confirm the presence of ciliated pseudostratified columnar epithelium, cartilage, smooth muscle, and other respiratory tissue components.

Treatment / Management

The strategies employed when managing and treating bronchogenic cysts are primarily based on the cyst's size, location, symptomatology, and potential complications. While many bronchogenic cysts are asymptomatic and discovered incidentally, symptomatic or complicated cysts require more active management.

Observation of Asymptomatic Individuals

For patients with asymptomatic bronchogenic cysts, especially those diagnosed incidentally by imaging studies, a conservative approach may be appropriate. Regular follow-up with imaging, typically CT, is recommended. This is particularly relevant for small cysts that do not cause compressive symptoms. However, the management of asymptomatic bronchogenic cysts remains controversial. Most authors seem to advocate a surgical approach to prevent complications.[5][15](B2)

While a conservative approach may be considered for adults, given that these lesions do not regress spontaneously, surgical excision is often recommended for children and young, healthy adults due to the risk of complications such as infection, erosion, or malignancy.[21] Even in cases where the neonate or infant is asymptomatic or prenatal ultrasonography suggests a vanishing lesion, further evaluation is still necessary. Postnatal investigations, including CT and consultation with a pediatric surgeon, are essential to address potential long-term complications.[22](B3)

Surgical Intervention

The gold standard therapeutic intervention for a bronchogenic cyst remains surgical excision, which offers excellent long-term outcomes free of recurrence and low perioperative morbidity and mortality. Surgical intervention is typically warranted in the following clinical scenarios:

• Symptomatic cysts causing respiratory distress, cough, or chest pain
• Cysts that are infected or suspected of having become infected which can lead to complications such as abscess formation
• Cysts causing significant compression of adjacent structures, including the tracheobronchial tree or lung parenchyma
• Suspected malignancy or malignant transformation of the cyst

Surgical Approaches

Surgical excision is the standard treatment for symptomatic and some asymptomatic bronchogenic cysts. Both open and minimally invasive procedures are used; the approach can vary depending on the cyst's location and the patient's status.

Open surgical resection

In cases where cysts are more extensive or complicated, an open surgical approach may be necessary.[16] This can involve thoracotomy for better access to the cyst, especially in complex mediastinal cases where adhesions increase the risk of incomplete resection; destruction of residual mucosa is required to prevent fluid accumulation and late recurrence.[23] Additionally, some patients do not tolerate thoracoscopy well. Thus, thoracotomy is the procedure usually performed.

Thoracoscopic surgery

Resection via video-assisted thoracoscopic surgery (VATS) has emerged as a viable approach and is often employed for cysts located in the lung parenchyma or mediastinum. This minimally invasive technique allows for effective removal with reduced recovery time and morbidity. With the adoption of the robotic platform for minimally invasive thoracic surgery, thoracoscopic resection has become more feasible. The transition from open to video-assisted thoracoscopic surgery (VATS) to robotic-assisted thoracoscopy has been associated with few complications.[24] A purely thoracoscopic procedure, which is even less invasive than VATS, offers advantages such as faster recovery and improved cosmetic outcomes. As demonstrated in some instances, this approach is feasible even in the confined spaces of younger patients, and it should be considered when the patient can tolerate it.[13][14](B2)

Choice of procedure

Regardless of the chosen surgical approach, the procedure performed will vary. For example, lobectomy is the procedure of choice for intrapulmonary bronchogenic cysts, whereas a conservative procedure such as a total pericystectomy, a wedge resection, or segmentectomy is recommended for peripheral bronchogenic cysts or patients with limited lung function. 

Minimally Invasive Techniques

Aspiration and drainage of symptomatic bronchogenic cysts can be performed using minimally invasive techniques, such as percutaneous access guided by ultrasound or endobronchial ultrasound-guided fine needle aspiration (EBUS-FNA). While EBUS-FNA is primarily a diagnostic tool, some specialists have successfully used this technique to drain bronchogenic cysts. However, this option is generally unavailable for young children, as bronchoscopy with EBUS-FNA is not typically performed in this age group. Drainage may be considered for patients who are not suitable for surgery, but it is not an ideal long-term solution due to the persistent risks of infection or cyst recurrence. When drainage is performed, it often serves as a temporary measure to relieve symptoms and facilitate later surgical removal by reducing the cyst's size and inflammation.[25]

Management of Complications

Complications of bronchogenic cysts include infection and fistula formation. Infected bronchogenic cysts may require a combination of surgical drainage and antibiotic therapy. Surgical drainage is typically necessary to relieve symptoms and prevent further complications if the cyst has formed an abscess. If a bronchogenic cyst has fistulized, surgical intervention is needed to close the communication with the bronchial tree and manage associated symptoms such as cough or hemoptysis.

Symptomatic Treatment

Patients with symptomatic cysts, particularly those experiencing chest pain, may require analgesics or anti-inflammatory medications to manage discomfort. If bronchogenic cysts lead to airway obstruction or bronchospasm, bronchodilators may be prescribed to improve airflow.

Differential Diagnosis

The differential diagnosis of bronchogenic cysts is broad and includes other cystic and solid lesions in the mediastinum, lungs, and elsewhere along the foregut development pathway, as well as conditions that may present with similar symptoms. Key differential diagnoses includeing:

• Thymic cysts
• Pericardial cysts
• Esophageal duplication cysts [26]
• Neurogenic tumors
• Lymphangiomas
• Hydatid cysts
• Pulmonary sequestration
• Malignant lesions
• Cystic teratomas and germ cell tumors
• Pulmonary abscess
• Fungal disease
• Tuberculosis
• Infected bullae
• Vascular malformations
• Neoplasms
• Cervical cystic mass [27]

Prognosis

The prognosis of bronchogenic cysts after surgical excision is excellent. In case of incomplete excision, late recurrences can occur.[28] A recent study reviewing 102 patients treated for bronchogenic cysts provided results demonstrating that the estimated mean morbidity and mortality was 20%.[29]

Complications

According to some authors, bronchogenic cysts lead to complications in 45% of patients, but complications do not increase morbidity or death.[30]

Complications encountered more frequently with bronchogenic cysts include:

• Tracheobronchial compression 
• Pneumonia
• Infected cysts

Rare complications comprise:

• Pneumothorax [31][32][33][34][35][36]
• Hydropneumothorax [37]
• Pleurisy
• Superior vena cava syndrome [38]
• Stenosis of the pulmonary artery
• Arrhythmias
• Air embolism 
• Malignant transformation [39]
• Myocardial infarction secondary to compression of the left main coronary artery
• Hemoptysis [40]
• Esophageal compression