Mediastinal cyst

Introduction The cyst of mediastinum is one of the mediastinal masses, and it belongs to the mediastinal tumor, but many people advocate it separately from the mediastinal tumor. The incidence of mediastinal cysts accounts for about 20% of all mediastinal masses. The mediastinal cyst is a benign lesion in the mediastinum. Can occur in the mediastinum of various organs, such as pericardium, trachea, bronchus, thoracic duct, lymphatics, thymus and so on. Occasionally there are hydatid cysts, acquired pancreatic cysts, and neurogenic intestinal cysts.

Cause

(1) Causes of the disease

It is caused by a variety of congenital dysplasia, such as tracheal and bronchial cysts derived from trachea or bronchial sprouts, gastric cysts and gastrointestinal cysts derived from the anterior intestine, and pericardial cysts due to abnormal development of mesodermal tissues. And cystic lymphangioma and the like. Such developmental abnormal cysts do not undergo malignant transformation; in addition, the mediastinal cysts include parasitic (such as cysticercosis) cysts, hematoma cystic changes and pancreatic pseudocysts.

(two) pathogenesis

1. Tracheobronchial cyst: Tracheobronchial cyst is the most common type of mediastinal congenital cyst of the mediastinum, accounting for 40% to 50%. Most of the tracheobronchial cysts occur on the 26th to 40th day after conception. The older ones form more mediastinal masses, while the later ones form more intrapulmonary masses. Individual cases are also found in the transverse or transverse The next one. The mediastinal tracheobronchial cyst can be divided into five groups according to the location of the trachea, around the carina, paraplegia, esophageal and other parts, most of which are located around the carina, and many pedicles are connected with the atmosphere. Cysts located around the carina are prone to clinical symptoms due to compression of adjacent tissues.

2. Esophageal cyst: The esophageal cyst is derived from the embryonic foregut and is the result of failure to form a normal lumen during esophageal development.

3. Gastrointestinal cysts: Gastrointestinal cysts are rare. There are several theoretical explanations about its origin, and it is believed that the early endoderm and the notochord are not completely separated. The lining cells of the gastrointestinal cyst include gastric mucosal epithelial cells, intestinal epithelial cells, and ciliated columnar epithelial cells, wherein the gastric mucosal epithelial cells may have a secretory function, leading to peptic ulcer.

4. Pericardial cysts: most of the pericardial cysts are congenital diseases, and in some cases, pericardial cysts can occur after many years of acute pericarditis. The pericardial cyst is generally fusiform or ovoid, with a thin wall and a clear or straw yellow liquid. The wall of the capsule is covered by a single layer of flat or columnar cells, and the cell morphology resembles mesothelial cells.

5. Thymic cysts: Thymic cysts are rare, accounting for only 1% to 2% of all mediastinal masses. Most of the congenital cysts from the thymic pharyngeal epithelium can occur anywhere from the neck to the descending line of the anterior mediastinum; there have also been reports of related trauma and inflammation. Pathologically, thymic cysts should be differentiated from pseudocysts formed by thymoma and Hodgkin's disease. The pseudocyst wall is generally thick, and residual tumor tissue can be found in the fibrous wall.

an examination

Related inspection

Chest CT examination of mediastinoscopy spiral CT

Tracheobronchial cyst

Chest X-ray examination of common mediastinal masses with clear, uniform texture of the mediastinum, mostly round or oval, and its shape can change with respiratory movement. Also visible in other parts of the mediastinum. Generally no lobulation, no calcification. Cysts under the carina can increase the angle of the bulge. The esophageal cyst examination showed that the esophagus was significantly stressed. In the case of secondary infection with the airway, the cyst can be enlarged in a short period of time, and a gas-liquid level can occur. Thoracic CT scan can determine the location of the cyst and its relationship with the surrounding structure. The typical cyst is round or oval, CT value is 0 ~ 20HU, the wall is very thin; CT value of liquid protein content in the capsule is high Increased, repeated chronic infection of the wall can be thickened.

2. Esophageal cyst

Chest X-ray examination showed that the lesion was located next to the esophagus in the posterior mediastinum, round or oval, with clear boundaries. Esophageal swallowing examination showed obvious pressure on the esophagus, but the mucosal folds were intact. If the cyst is ulcerated and communicates with the esophagus, gas can be seen in the cyst, and the expectorant can enter the cyst when swallowing. The esophageal cyst and the bronchial cyst located next to the esophagus have the same X-ray findings, which are difficult to identify and often require a postoperative pathological examination to confirm the diagnosis.

3. Gastrointestinal cyst

Chest X-ray examination showed that the cyst was located next to the mediastinal spine, round or elliptical, with a clear and uniform outline and uniform density. Esophageal cysts are often connected to the meninges and gastrointestinal tract through the pedicle. If the joint is located in the thoracic esophagus, there is no traffic; on the contrary, if the joint is located in the abdominal gastrointestinal tract, most of the traffic is in between, and air can enter the cyst. The sputum can also enter the capsule during angiography. Commonly seen thoracic and cervical deformities, such as semi-spinal deformity, posterior spina, scoliosis and so on.

4. Pericardial cyst

Chest X-ray examination showed that the pericardial cyst is usually located in the anterior mediastinal palpebral palpebral area, but there are also higher positions. A few patients can extend to the upper mediastinum, and the right side is more common than the left side. The cyst has a clear and smooth outline with uniform density and generally no calcification. Sometimes in the lateral chest radiograph, the cyst has a drop-like shadow on the tip of the drop, which may be formed by the cyst embedded in the interlobular fissure, which has certain characteristics. Most cysts range in diameter from 3 cm to 8 cm, but are reported as small as 1 cm and as large as 28 cm. CT examinations help to define the cystic structure of the shadows and have a higher diagnostic value for atypical areas. The morphology of the cyst under fluoroscopy can vary with positional changes and respiratory movements.

5. Thymic cyst

Chest X-ray examination showed no specificity, and the cyst edge was smooth, round or oval, and was located in the anterior mediastinum. CT and magnetic resonance examinations help to define cystic features.

Differential diagnosis

Mediastinal cysts need to be differentiated from mediastinal tumors; such as thoracic aortic aneurysm or multiple aneurysms, paraspinal abscesses, central lung cancer, mediastinal lymphadenopathy, pulmonary suppuration, ventricular aneurysm, etc.

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