Mediastinal cyst are a large group of cavity formations of mediastinal space of congenital and acquired nature. Pathology may have an asymptomatic course or be accompanied by signs of compression of surrounding organs (bronchi, esophagus, atria, arteries), disrupting their function. Diagnosis involves polypositional X-ray and chest X-ray, esophagus, heart; tomography; bronchoscopy, pneumomediastinography, mediastinoscopy, fine needle aspiration biopsy, ultrasound of the mediastinum, parasternal mediastinotomy. Treatment may include their open or thoracoscopic removal, transthoracic puncture of the cyst with drainage and sclerosis, etc.
ICD 10
Q34.1 D15.2
Meaning
Mediastinal cysts account for 14 to 18.5% of all mediastinal pathology. Mediastinal cysts include cavities of various genesis, originating from heterogeneous tissues and united by anatomical and topographic features of the location. They are mainly found in patients aged 20-50 years, with the same frequency in women and men.
In addition to cysts, true benign and malignant tumors can develop in the mediastinum: thymomas, teratomas, lipomas, neurogenic tumors, lymphomas, sarcomas, lymphogenic metastases of malignant tumors of various organs, etc. The problem of diagnosis and treatment of mediastinal cysts is one of the most complex and relevant sections of pulmonology and thoracic surgery.
Anatomy of the mediastinum
The mediastinum is understood as an anatomically complex space located in the thoracic cavity. In front, the boundaries of the mediastinum are the sternum, the post-thoracic fascia and costal cartilages; behind – the pre-vertebral fascia, the anterior surface of the thoracic spine and the neck of the ribs; on the sides – the leaves of the mediastinal pleura; from below – the diaphragm; from above – a conditional horizontal plane passing along the upper edge of the handle of the sternum. Thus, in the mediastinal space there are 3 departments (anterior, middle and posterior mediastinum) and 3 floors (upper, middle and lower mediastinum).
Vital organs and anatomical formations (large vessels, nerve trunks and plexuses, lymphatic ducts, tracheal bifurcation and main bronchi, esophagus, pericardium, etc.) are concentrated in the mediastinum. Therefore, compression or invasion of these structures can be accompanied by various manifestations and often life-threatening symptom complexes. Mediastinal cysts can be detected in any departments and floors of the mediastinal space.
Classification
Mediastinal cysts are classified by origin and localization. Among the many mediastinal cysts, true (congenital, primary), secondary (acquired) are distinguished.
Congenital mediastinal cysts develop from mesodermal formations – the coeloma or anterior intestine. These include coelomic, enterogenic, bronchogenic, dermoid cysts, thymus cysts, etc. Acquired mediastinal cysts originate from lymphatic vessels, various mediastinal organs and border areas. Acquired mediastinal cysts include lymphatic, thymus, parasitic (echinococcal), meningeal.
Coelomic cysts and diverticula of the pericardium
They are a kind of congenital malformation and account for 3.3-14.2% of all mediastinal neoplasms. Most often, pericardial cysts (60%) develop in the right cardiodiaphragmal corner, less often (30%) – in the left cardiodiaphragmal corner and other parts of the mediastinum (10%). Such mediastinal cysts are hollow thin-walled formations similar in structure to pericardial tissues, have a smooth surface of gray-yellow or gray color.
Pericardial cysts contain clear serous or serous hemorrhagic fluid. Coelomic cysts of the pericardium can reach a diameter of 3 to 20 cm or more. Coelomic cysts of the mediastinum can be single-chamber or multi-chamber, communicate with the pericardial cavity, be connected to the pericardium by means of a pedicle or planar fusion. Acquired pericardial cysts are rare; they usually have an inflammatory and traumatic origin. Parasitic (echinococcal) cysts of the pericardium are also described.
Bronchogenic mediastinal cysts
They occur in 30-35% of observations. They are also malformations of embryonic development and are formed from areas of dystopian bronchial epithelium. Macroscopically, they represent thin-walled formations filled with a transparent, rarely brown liquid. Histological examination reveals cartilage tissue, connective tissue and smooth muscle fibers of the mucous glands.
The cavity of the bronchogenic cyst of the mediastinum is lined from the inside with a cylindrical or ciliated epithelium. Inside the cyst contains a transparent or turbid gelatinous, viscous mass, which, if there is a connection between the cyst and the bronchial tree, can be suppressed. Bronchogenic mediastinal cysts are usually located behind the tracheal bifurcation and are in close contact with the trachea or the main bronchi, sometimes with the esophagus. They usually have a single-chamber structure and reach sizes of 7-10 cm in diameter.
Gastroenterogenic mediastinal cysts
Enterocystomas are embryonic derivatives from the primary intestine. Taking into account the microscopic similarity of their structure with the gastrointestinal tract, esophageal, gastric and intestinal cysts are isolated. Gastroenterogenic mediastinal cysts occur in 0.7-5% of cases. They are single-chamber rounded or ovoid formations, with thick walls and a leg; they are localized mainly in the posterior mediastinum. Gastroenterogenic mediastinal cysts contain a cloudy mucus-like mass. Gastric cysts can produce hydrochloric acid, which leads to ulceration of the walls, bleeding, ulcers and perforation of the walls of the mediastinal cyst. In rare cases, cancer can develop in the cyst wall.
Dermoid cysts of the mediastinum
Cystic teratomas contain ectoderm elements in their structure and arise in the process of violation of embryogenesis. In medicine, there are dermoid cysts of the ovaries, abdominal wall, skin, retroperitoneal tissue, liver, kidneys, etc. organs and tissues. Dermoid cysts are usually located in the anteroposterior part of the mediastinum. The size of dermoid cysts of the mediastinum can reach 15-25 cm . The shape of cystic teratomas is usually irregular oval; the consistency is elastic or soft. The walls of the cyst may contain cartilaginous and calcareous inclusions. Inside the cyst is a thick, mushy fatty mass with many different inclusions (hair, epidermis scales, cholesterol crystals, amorphous fats, teeth).
Thymus gland cysts
They may have congenital and acquired (inflammatory, tumor) origin. They are mainly detected in children and young people.
Symptoms
Features of clinical manifestations of mediastinal cyst are determined by the type and location of the formation, its size and growth rate. In most cases, symptoms develop at the stage when an increase in the mediastinal cyst causes compression of other organs and an inevitable violation of their functions.
The course of pericardial cysts in most cases is asymptomatic, smooth. They are often a godsend when undergoing preventive fluorography. Sometimes there are palpitations, shortness of breath, dry cough that occur when changing the position of the trunk and physical exertion. With a complicated course of coelomic mediastinal cysts, there may be a sinking of the contents of the pericardial cyst into the bronchi, suppuration and cyst ruptures.
The development of bronchogenic mediastinal cysts is often accompanied by a persistent cough, shortness of breath, dysphagia, and dull chest pain. When the cyst squeezes the airways, stridorous breathing develops. In the case of a breakthrough of a bronchogenic cyst of the mediastinum, hemoptysis may appear in the bronchus. With the simultaneous breakthrough of the cyst into the pleural cavity and into the bronchi, a hydropneumothorax and bronchopleural fistula develop.
Gastroenterogenic mediastinal cysts manifest themselves by coughing, shortness of breath, tachycardia, dysphagia, chest pain. Enterocystomas can break into the trachea, bronchi, pleural cavity, mediastinum, causing the development of hemoptysis, pleural empyema, frequent pneumonia, fever of unknown genesis, bronchiectasis, mediastinitis.
In more than half of cases, a dermoid cyst of the mediastinum is accompanied by various cardiovascular disorders: angina attacks, pain in the heart, tachycardia. In 30% of patients, a sign of a dermoid cyst of the mediastinum is the appearance of a productive cough with the release of a mushy mass containing an admixture of hair and fat, which is observed when the cyst breaks into the bronchus. In some patients, there is a protrusion of the chest wall in the projection of the location of the tumor.
The symptoms of thymus cysts can be diverse – from asymptomatic to complicated. Having reached a known size, cysts can cause mediastinal “compression” syndrome. In some cases, myasthenic syndrome comes to the fore. The danger of thymus cysts lies in the risk of suppuration, breakthrough into the pleura, bleeding.
Complications
The most formidable complication of mediastinal cysts is the so-called mediastinal compression syndrome, the frequency of which ranges from 27 to 39%. This may include compression of the respiratory tract, superior vena cava syndrome (SVC), compression of the esophagus, heart, recurrent nerve.
With compression of the respiratory tract, stridorous breathing, shortness of breath, respiratory failure develops. SVC syndrome is manifested by cyanosis of the skin of the face, visible mucous membranes, neck, upper extremities and chest; swelling of the soft tissues of this zone; dilation and tension of the neck veins; increased pressure in the SVC system. Compression by cysts of various mediastinal structures can be accompanied by dysphagia, epiglottis dysfunction, dysphonia, compression and dislocation of the heart.
Other complications of mediastinal cysts include their breakthroughs in the pleural cavity, bronchi and lung, bleeding into the mediastinum and pleural cavity (hemothorax). The complicated course of mediastinal cysts carries a potential threat to the patient’s life.
Diagnostics
Methods for detecting mediastinal cysts include X-ray, ultrasound, tomographic, endoscopic, morphological diagnostics.
- X-ray examinations. Polypositional X-ray and chest X-ray, X-ray of the esophagus and heart, pneumomediastinography make it possible to determine the localization, shape and size of the cyst, its connection with neighboring organs, changes in position during respiratory movements.
- Tomographic diagnostics. For a more detailed assessment of the structure, thickness of the walls of the cyst, the nature of the contents and the relationship with neighboring anatomical formations, CT and MRI of the mediastinum are performed.
- Echography. In mediastinal neoplasms, mediastinal ultrasound is widely used in diagnostic practice. EchoCG helps significantly in the diagnosis of pericardial cysts, which allows differentiating a mediastinal cyst from lung cysts, dermoid mediastinal cysts, and aortic aneurysms.
- Bronchological examination. With mediastinal cysts that demonstrate an intimate connection with the trachea or bronchi, bronchoscopy and bronchography are resorted to.
If these diagnostic methods do not allow to determine the nosology of education, it is advisable to switch to invasive diagnostic studies:
- Biopsy. Aspiration fine-needle biopsy of the mediastinal cyst makes it possible to carry out a cytological examination of the obtained punctate and verify the morphology of the formation in 80-90% of cases. Fine needle biopsy can be performed by percutaneous, transstracheal, transbronchial, transesophageal access.
- Diagnostic operations. Mediastinoscopy, diagnostic thoracoscopy, and parasternal mediastinotomy can be performed for the purpose of visualization and open excision biopsy of a mediastinal tumor.
Treatment
Therapeutic tactics in relation to mediastinal cysts are reduced to their surgical removal at the earliest possible time. This approach is the prevention of the development of compression syndrome, rupture and malignancy of mediastinal cysts.
- Open removal of a mediastinal cyst can be performed by longitudinal sternotomy (when the cyst is located in the anterior mediastinum), using an anterolateral thoracotomy on the side of the lesion (when the formation is located laterally), lateral thoracotomy (when the tumor is localized in the middle mediastinum), posterolateral thoracotomy (when the cyst is located in the posterior mediastinum). Open operations provide the possibility of the greatest freedom of action and a full-fledged intraoperative revision of the wound. With the development of complications, a mediastinotomy may be required.
- Thoracoscopic removal of mediastinal cysts is also widely and successfully used not only for diagnosis, but also for the removal of mediastinal formations. In some cases, a mini-thoracotomy with video support is used.
- Puncture aspiration. In somatically burdened patients with low functional reserves, the method of choice is transthoracic puncture with drainage and sclerosis of the mediastinal cyst. As sclerosants, a solution of alcohol with iodine, glucose is usually used.
Literature
- Surgical treatment of mediastinal cysts: report on 29 cases. Aydin Y, Ogul H, Turkyilmaz A, Eroglu A. Acta Chir Belg. 2012 Jul-Aug;112(4):281-6. link
- Mediastinal cysts, surgical management. Safránek J, Spidlen V, Vodicka J. Rozhl Chir. 2011 May;90(5):277-80. link
- Benign cysts of the mediastinum: series of 28 cases. Traibi A, El Hammoumi M, El Oueriachi F, Arsalane A, Kabiri EH. Rev Mal Respir. 2012 Nov;29(9):1111-5. link
- Mediastinal cysts: clinical approach and treatment. Le Pimpec-Barthes F, Cazes A, Bagan P, Badia A, Vlas C, Hernigou A, Pricopi C, Riquet M. Rev Pneumol Clin. 2010 Feb;66(1):52-62. link
- A variety of mediastinal bronchogenic cyst: the broncho-alveolar cyst. Anichini C, Comin CE. Pathologica. 1997 Dec;89(6):729-32. link