What is Bronchogenic Cyst?
Bronchogenic cysts are abnormal growths originating from the part of the embryo that develops into the respiratory tract. They typically form in the chest area during early development or in the lungs during later development. However, they can appear anywhere along the developmental path in unusual locations. These cysts usually show a variety of symptoms and appearances on scans, which can often be confused with a disease called hydatid disease in countries where it’s widespread. The common treatment for all such cysts is complete surgical removal, and a definitive diagnosis is confirmed mainly by examining the removed cyst under a microscope. If the entire cyst is removed, the outlook is generally excellent with no further occurrences.
What Causes Bronchogenic Cyst?
Bronchogenic cysts are formed due to an abnormal or late development of the early lung or the airway tree in embryos between the 26th and 40th days of pregnancy. This unusual growth then turns into a fluid-filled, dead-end pouch. Where these cysts are found depends on when this abnormal growth takes place during the development of the embryo.
If this irregular growth happens early in the development process, the cyst will be located in the airway tree. However, if it occurs later, the cyst may be more on the outer side and could affect the lung tissue itself.
Risk Factors and Frequency for Bronchogenic Cyst
Bronchogenic cysts are unusual cystic conditions found in between 1 per 42,000 and 1 per 68,000 hospital patients. More often seen in men, these cysts are often not detected until a person is in their third or fourth decade of life. They make up between 10% to 15% of mediastinal (the part of the body between the lungs) tumors and represent between 50 to 60% of all mediastinal cysts. These cysts primarily occur in the middle section of the mediastinum, especially close to the windpipe and the area where the windpipe splits into different directions.
According to their positions, mediastinal bronchogenic cysts are categorized into five different types:
- Paratracheal
- Carinal
- Paraesophageal
- Hilar
- Miscellaneous
Intrapulmonary bronchogenic cysts, which are found within the lungs, consist of 20% to 30% of cases and they mostly occur in the lower parts of the lungs. They do not prefer one lung over the other. Other locations, such as the heart lining, the lung lining, the neck, the diaphragm, and area beneath the stomach, for bronchogenic cysts are extremely rare.
Signs and Symptoms of Bronchogenic Cyst
In children, certain types of cysts in the lungs called bronchogenic cysts can cause life-threatening symptoms due to pressure they exert on surrounding body structures. However, in adults, these cysts are often discovered unintentionally during unrelated medical imaging procedures.
Lung-based bronchogenic cysts are more likely to cause symptoms than those located in the space in the chest between the lungs, known as the mediastinum. The majority of people who experience symptoms from these cysts have a complicated cyst, meaning it’s causing other health issues.
- These symptoms occur due to infection of the cyst or compression of nearby body structures.
- If a bronchogenic cyst develops a connection to a nearby body cavity or skin surface (fistulizes), it can cause coughing, fever, the production of mucus, and coughing up blood.
- Non-fistulized bronchogenic cysts typically cause chest pain.
- An inflammation around the cyst (pericystic pneumonitis) or pneumonia in the lung area compressed by the cyst can cause fever and difficulty breathing.
Testing for Bronchogenic Cyst
Finding bronchogenic cysts, a type of cyst found in the lungs or chest, can be done through different tests:
Chest X-rays, where these cysts show up as clearly outlined, solitary, round, or oval shapes, often in the lower part of the lung. They may appear similar to the density of water, filled with air, or having a level of air and fluid. Sometimes, they can be harder to spot if there’s a collapse or inflammation around the lung tissue where the cyst is located.
CT, or computed tomography, scans are the best choice of test for detecting these cysts. These cysts can show up on the scans with a range of different densities, from that of water to more dense cysts which may be due to blood, increased calcium, different pigments, or a higher protein level in the fluid.
Magnetic resonance imaging (MRI) is another option. It might be better than a CT scan for getting a detailed picture of the cyst and its proximity to other body parts. The appearance of the cyst in the MRI depends on what’s inside the cyst – the ‘T1-weighted images’ show signal intensity ranging from low to high based on the content, while the ‘T2-weighted images’ show a high signal intensity. Contrast injection is often used to enhance the images, but with bronchogenic cysts, this doesn’t usually occur.
Treatment Options for Bronchogenic Cyst
The treatment plan for individuals diagnosed with bronchogenic cysts depends greatly on their symptoms and age. Surgical removal is usually the best way to alleviate symptoms, prevent complications and confirm the diagnosis.
Regardless of age, if a patient is showing symptoms of the cyst, it should be removed via surgical methods. This can be achieved through thoracotomy, which is an incision made into the chest, or by using video assistance to visualize the area. The only times these operations are not recommended is if the surgical risks are too high for the specific patient.
Recently, there has been an increase in the use of video-assisted surgery for removing bronchogenic cysts in adults. The advantages of this method are reduced scarring, less pain after surgery, and the patient can leave the hospital sooner. However, for complicated cases of bronchogenic cysts, the traditional thoracotomy approach might be necessary as it enables the doctor to carry out a more extensive surgery.
It’s crucial that the surgical removal is carried out thoroughly to avoid the cyst growing back. For patients who have bronchogenic cysts but aren’t showing symptoms, there’s ongoing debate about the best form of treatment. Despite this, most medical professionals recommend surgery to prevent potential complications.
For bronchogenic cysts located in the lungs, a lobectomy, the removal of a lobe of the lung, is usually the best treatment. However, if the cyst is on the edge of the lung or the patient has compromised lung function, a less extensive procedure, such as removing a small slice of lung tissue (wedge resection) or only a part of one lobe (segmentectomy), could be recommended instead.
For bronchogenic cysts located in the area between the lungs (mediastinum), the presence of scar tissue or complex cysts may cause the surgery to be incomplete. To stop the fluid from building up and the cyst potentially returning, the lining of the cyst needs to be removed or destroyed.
Another option for managing bronchogenic cysts is to closely monitor them through imaging techniques over time to make sure they do not change in size.
What else can Bronchogenic Cyst be?
When examining X-ray or scan results, doctors may need to distinguish between a number of conditions that can appear similar to each other, these include:
- Lung abscesses, which are pockets of pus in the lung
- Hydatid cysts, a type of parasitic infection
- Fungal infections that affect the lungs
- Tuberculosis, a serious bacterial lung infection
- Infected bullae, which are large air spaces in the lung
- Vascular malformations, which are abnormal blood vessels in the lungs
- Various types of lung tumors
On the other hand, when looking at tissue sample results under a microscope, doctors might need to rule out:
- Cystic teratoma, a type of noncancerous tumor
- Bronchopulmonary sequestration, a congenital lung condition
- Esophageal cysts, which are fluid-filled sacs in the esophagus
- Abscesses that have healed and become chronic
It’s crucial to accurately differentiate between these conditions to ensure the right treatment is given.
What to expect with Bronchogenic Cyst
The outlook is generally excellent following the surgical removal of bronchogenic cysts. However, if the cyst is not completely removed, there’s a chance it can come back at a later time. According to a recent study that reviewed 102 patients who underwent treatment for bronchogenic cysts, the estimated average rate of complications and fatality was 20%.
Possible Complications When Diagnosed with Bronchogenic Cyst
Some researchers suggest that bronchogenic cysts – which are rare malformations of the airway – can lead to complications in around 45% of patients. However, these complications do not significantly increase overall illness and risk of death.
The potential complications of bronchogenic cysts include:
- Airway (the path that air follows to get into and out of the lungs) and lung infections
Less common complications might be:
- A collapsed lung (also called pneumothorax)
- Inflammation of the lining of the lungs and chest (also known as pleurisy)
- Condition where the blood flow through the large blood vessel (superior vena cava) carrying de-oxygenated blood to the heart is blocked
- Narrowing of the pulmonary artery that carries low oxygen blood to the lungs
- Arrhythmias (irregular heartbeats)
- Air embolism (air bubbles enter the veins or arteries) in airplane passengers
- Transitioning to cancer (Malignant transformation)
- Fatal heart attack (also known as myocardial infarction) due to the compression of the left main coronary artery- the artery that provides blood flow to the heart muscles
