Thymic cyst

Introduction to thymic cyst Thymic cysts are only one type of many intrathoracic mediastinal cysts, and the mediastinal cysts are complex and diverse. The causes of the disease are mostly congenital, and a few are acquired, but there is no clear cause. The thymus is located in the neck during the embryonic stage, and moves to the anterior mediastinum. At the 6th week of the embryo, a primordial thymocyte grows on the ventral side of the third pharyngeal sac, and at the 7th week, the third pharyngeal sac separates from the pharynx. And from the hollow primordium to the solid epithelial column, to the 8th week, the tail end is swollen, attached to the surface of the anterior wall of the pericardium, the attachment of the pericardium accelerates the thymus into the chest, to the fetus 3 months old At the end, the thymus has differentiated into cortex and medulla. After development, the two leaves are lying on the anterior wall of the pericardium and large blood vessels. It is believed that the benign process is due to the degradation of the thymus gland and the partial retention of the thymic pharyngeal duct. It is reported that thymic cysts can be found in children with congenital syphilis or tuberculosis. Most of the reports are congenital. It has been reported that thymic cysts occur after correction of cardiac anterior sternal median incision, but rare, in the diagnosis of Hodgkin's disease in the mediastinum. The nodular sclerosing Hodgkin's disease can occur in cystic lesions of the thymus with thymic cysts. Histologically, the thymic cyst has a squamous epithelial lining, and there is a normal thymus residue in the cyst wall. There is serous fluid or intracapsular hemorrhage in the capsule. Cholesterol crystal is a typical manifestation of cyst regression, and thymus tissue on the wall is the main diagnostic feature. basic knowledge The proportion of illness: 0.005%--0.01% Susceptible people: no specific population Mode of infection: non-infectious Complications: congenital thymic hypoplasia thymoma

Cause of thymic cyst

(1) Causes of the disease

It is currently believed that thymic cysts are congenital, because thymic cysts are found on the thymus development line, such as the neck and mediastinum, thymic cysts account for about 1% of mediastinal tumors and cysts.

(two) pathogenesis

The thymus is located in the neck during the embryonic stage, and moves to the anterior mediastinum. At the 6th week of the embryo, a primordial thymocyte grows on the ventral side of the third pharyngeal sac, and at the 7th week, the third pharyngeal sac separates from the pharynx. And from the hollow primordium to the solid epithelial column, to the 8th week, the tail end is swollen, attached to the surface of the anterior wall of the pericardium, the attachment of the pericardium accelerates the thymus into the chest, to the fetus 3 months old At the end, the thymus has differentiated into cortex and medulla. After development, the two leaves are lying on the anterior wall of the pericardium and large blood vessels. It is believed that the benign process is due to the degradation of the thymus gland and the partial retention of the thymic pharyngeal duct. It is reported that thymic cysts can be found in children with congenital syphilis or tuberculosis. Most of the reports are congenital. It has been reported that thymic cysts occur after correction of cardiac anterior sternal median incision, but rare, in the diagnosis of Hodgkin's disease in the mediastinum. The nodular sclerosing Hodgkin's disease can occur in cystic lesions of the thymus with thymic cysts.

Histologically, the thymic cyst has a squamous epithelial lining, and there is a normal thymus residue in the cyst wall. There is serous fluid or intracapsular hemorrhage in the capsule. Cholesterol crystal is a typical manifestation of cyst regression, and thymus tissue on the wall is the main diagnostic feature.

Thymic cyst prevention

Since the disease is a congenital disease, the key to prevention is early detection and early treatment.

Thymic cyst complications Complications Congenital thymic hypoplasia thymoma

The disease can cause compression of the thymus and compression of the mediastinum. The compression of the thymus can affect the development of the thymus, causing thymic dysplasia and affecting the body's immune system. For patients with mediastinal compression, due to compression of large blood vessels and heart tissue, patients may have clinical manifestations such as palpitations and palpitation. For patients with severe aorta compression, it can cause complications such as brain tissue ischemia.

Symptoms of thymic cysts Common symptoms Cysts shortness of breath Chronic mediastinal cysts

The clinical symptoms of thymic cysts depend on the location of the cyst. The cervical thymic cyst is more common in patients 10 to 20 years old. It often presents as a neck mass with few clinical symptoms unless the volume of the cyst changes drastically, such as intracapsular hemorrhage, mediastinum. The internal thymic cysts are mostly 30 to 60 years old, and clinical symptoms are rare in the early stage. A small number of patients with mediastinal thymic cysts may have shortness of breath, cough and chest pain. In the physical examination, X-ray films were found in 90% of patients. Painless mass, the mass is mostly located in the left neck (70%), the right side (23%), the midline and throat accounted for 7%, some patients may be affected by cyst infection or bleeding, the mediastinal thymus A small number of cysts were discovered only during heart surgery.

Examination of thymic cyst

1. Chest X-ray examination helps to understand the size of the mass, but it is difficult to find when the volume is small and hidden in the mediastinum shadow. When the cyst is enlarged to a certain volume, it can be semi-circular or curved in the front upper mediastinum. The edges are smooth and clear, the density is high, and sometimes the edges are calcified.

2. Ultrasound examination can understand the size of the mass, the outer shell and the presence of a central fluid, and echocardiography can determine the extracardiac cystic mass, which provides less information than CT.

3. CT scan shows a clearer capsule content density close to water, except for intracapsular hemorrhage or cyst wall degeneration, and can understand the sub-cavity in the capsule, which is distinguished from the solid new organism, which generally contains a thin liquid with low density. But after bleeding, it can be high density.

4. Needle biopsy has little value for cytology, as there is thymus tissue on the wall of the cyst for histological diagnosis.

Diagnosis and differentiation of thymic cyst

diagnosis

In the anterior mediastinum, a cystic mass is found. The possibility of thymic cyst should be thought of. The cervical thymic cyst can be found by physical examination. The cyst in the mediastinum is mainly found by chest X-ray. The CT scan is used to determine the nature of the cyst and the extent of the cyst. Important value, ultrasound examination is also helpful in the diagnosis of thymic cysts. Acupuncture biopsy cysts have thymus tissue on the wall to confirm the diagnosis.

Differential diagnosis

Thymic cysts are difficult to diagnose before surgery. Because their position and shape can be misdiagnosed as "thymoma", they can be misdiagnosed as "teratoma" due to calcification. When they are close to the pericardium, they can see the conductive pulsation and are misdiagnosed as "aortic aneurysm." "Surgical exploration can be identified."

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