Thymoma

Introduction to thymoma The thymus is an important immune origin of the human body. It originates from the third (or fourth) sacral endoderm in the embryonic period. It is a derivative of the primitive foregut epithelial cells. It is attached to the anterior mediastinum with embryonic growth and development. It has unique clinical pathological features and is associated with it. A disease with paraneoplastic symptoms. Thymoma is a tumor derived from the thymic epithelium, accounting for about 50% of the anterior mediastinal tumor. The clinical manifestations vary, often accompanied by many autoimmune abnormalities. Recently, the understanding of autoimmune enteropathy is gradually affected. Pay attention to it, but its incidence rate is not clearly reported. basic knowledge The proportion of illness: the incidence rate is about 0.002%-0.005% Susceptible people: no specific population Mode of infection: non-infectious Complications: myasthenia gravis nephrotic syndrome

Thymoma cause

Thymic epithelial cells (30%):

Thymic tumors originating from thymic epithelial cells or lymphocytes are the most common. 95% of thymic tumors rank first to third in the entire mediastinal tumor. Most thymoma is benign in histocytology, but some of them are biological. Behaviorally invasive growth, malignant thymoma malignant thymoma also includes thymic carcinoma, which is a typical malignant feature of histological cytology.

Compression of surrounding organs (30%):

Like any mediastinal tumor, the clinical symptoms of thymoma arise from compression of surrounding organs and symptoms characteristic of the tumor itself - the combined syndrome. Small thymoma has no clinical complaints and is not easy to be found. When the tumor grows to a certain volume, the common symptoms are chest pain, chest tightness, cough, and chest discomfort. The nature of chest pain is non-characteristic, the degree is not equal, and the site is not specific. Generally speaking, it is lighter and often treated symptomatically. No further examination is performed. Symptoms were delayed for a long time, some patients underwent X-ray examination, or some patients found shadows of mediastinal mass when examining chest or chest.

Superior vena cava obstruction syndrome (10%):

The neglected diagnosis of thymoma often grows to a considerable volume, with no signs of venous or superior vena cava syndrome. Severe chest pain, rapid symptoms in a short period of time, severe irritating cough, dyspnea caused by pleural effusion, pericardial effusion caused by palpitation, shortness of mind, and concern about bone pain, suggesting the possibility of malignant thymoma or thymic cancer.

Pathogenesis

Most thymoma is expansively growing and has a complete capsule. Even if the tumor is large, it is easy to completely remove. 30% to 60% of thymoma is invasive and can directly invade surrounding tissues and organs, such as mediastinal pleura, pericardium. , lungs, large blood vessels and nerves, extending to the neck and invading the thyroid gland, spreading down through the aortic sulcus to the infraorbital liver, around the kidney and the peritoneal blood vessels, the lymphatic metastasis of the thymoma is relatively small, and the lymph nodes that may be involved are in turn It is mediastinal lymph nodes, hilar lymph nodes, cervical lymph nodes, supraclavicular lymph nodes, axillary lymph nodes, hilar and mesenteric lymph nodes, etc., blood transfer is more rare, metastatic target organs and tissues are lung, liver, bone, kidney, brain, Spleen, adrenal gland, breast and ovary.

Pathological features: All thymoma originated from thymic epithelial cells, and only 4% of thymoma consisted of a single thymic epithelial cell. Most thymoma was composed of a mixture of thymic epithelial cells and lymphocytes.

1. Visual inspection: The volume of thymoma varies from 1.5 to 25 cm, more than 5 to 8 cm, and the weight is 10 to 1750 g, usually 20 to 200 g. The color is dark brown or grayish red. Round, elliptical or irregular, the surface is often nodular, benign, intact, no adhesion to the surrounding, invasive growth of malignant, incomplete capsule, rough surface, involving the pleura, pericardium, large blood vessels The tumor is soft in texture, and more than half of the capsules are attached with residual degenerative thymus adipose tissue. The tumor tumors are mostly substantial, and the cut surface is lobulated, with obvious gray-white fibrous tissue spacing, and the cut surface is grayish red or grayish white, showing coarse or fine particles. It is often accompanied by hemorrhage or cystic changes. The size of the capsule varies from 0.2cm microcapsules to large capsules with a diameter of about 10cm. Even most of the tumors are cystic, and the capsule wall is thin. Smooth, containing clear liquid or bloody fluid, can often see a variety of degenerative changes, such as hemorrhage, calcification and cystic changes, in addition to the entire thymus tissue has been replaced by thymoma tissue, most thymoma and normal Thymus tissue bordering

2. Microscopic structure: Victor and Thomas studies have shown that all thymoma are derived from thymic epithelial cells, and their epithelial components can be confirmed by immunohistochemistry techniques.

Lewis and other recommendations for thymoma are as follows: 1 epithelial thymoma, epithelial cells account for more than 66% of the total number of tumor cells; 2 lymphocytic thymoma, lymphocytes account for more than 66% of the total number of tumor cells; 3 are not consistent The above two types of tumors are classified as mixed thymoma; 4 tumors are composed of mutated epithelial cells classified as spindle-shaped thymoma, and thus some are called a subtype of epithelial cell type.

Classification: Domestic tends to be classified according to the characteristics of cell morphology and relative quantity. There is no clear concept of quantity, which is the following four types.

(1) Epithelial cell type: accounting for 27% to 34% of thymoma. The epithelial cells are mainly composed of different epithelial cells. The morphological changes are complex, round, oval or fusiform, and the cytoplasm is light. Translucent for eosinophilic staining or two-color staining, cell borders are unclear, nuclear chromatin is uniform, nucleoli is obvious, its shape is regular, nuclear membrane is clear, cells have clusters of habits, arranged in a sheet, nested , a variety of forms, such as strips, wire mesh, fissures or fake daisy-shaped clusters, the blood vessels are rich, the tumor cell mass is surrounded by fibrous tissue, and there are scattered and varying numbers of lymphocytes.

Under the electron microscope, the characteristics of tension fibrils and desmosome of epithelial cells can be seen.

The cytological characteristics of epithelial thymoma without malignant tumors, only 2% of epithelial thymoma atypical changes, pleomorphic, nuclear and cytoplasmic ratio increased, nuclear chromatin is dense, nucleoli visible small Splitting, this type of invasive growth is common and occasionally necrotic areas within the tumor.

(2) Lymphocyte type: 20% to 27%, the main component is lymphocytes.

The size of lymphocytes is small, round, the nucleus is large and reticular, the nucleolus is unclear, mature and there is no atypical manifestation, diffuse hyperplasia or nodular hyperplasia, see lymphatic germinal center, how much leaflet interval Different, there are scattered or focal, nested epithelial cells, common Hastelloy and microcalcification, blood vessels are rich, sometimes visible hyperplasia of capillary endothelial cells, lymphocytes in thymoma The response to polyclonal antisera markers is consistent with lymphocytes in normal thymus tissue and there are no signs of malignant transformation.

(3) Mixed type: 40% to 55%, the number of epithelial cells and lymphocytes are approximately equal, diffusely mixed or nodular, or the two cellular components are regionally distributed, and the boundary is obvious, often in a tumor. Different sections showed that the cell morphological components were very inconsistent, and the connective tissue in the stroma was obviously proliferated.

(4) spindle cell type: 2% to 4%, many scholars believe that it is a variant of epithelial cells, cells and nuclei are fusiform, closely arranged, sometimes spiral or fence-like, blood vessels are rich, Often mixed with epithelial cells, there is a migration relationship between the two, under the electron microscope can be seen.

The pathological tissue type of thymoma is not directly related to staging, and there are various options for staging of thymoma.

However, most of the spindle cell types grow in the envelope, while the epithelial cells are easy to infiltrate and grow outside the capsule. Therefore, most of the literature reports that epithelial cell type thymoma is more common in stage II and III.

The proportion of thymoma in each stage, most reports in the literature: 2 / 3 thymoma is stage I, less than 1/3 of thymoma is stage II ~ III.

Thymoma prevention

There is no effective preventive measure for this disease. Early diagnosis and early treatment is the key to the prevention and treatment of this disease. At the same time, attention should be paid to prevent the occurrence of various complications. Once it occurs, it should be actively treated to prevent further development of the disease.

Thymoma complications Complications Myasthenia gravis nephrotic syndrome

Common complications of this disease are:

1. Myasthenia gravis (MG)

For a long time, people have found that myasthenia gravis is related to thymus (or thymoma). Myasthenia gravis can be divided into 3 types clinically, such as drooping eyelids, long-term fatigue of vision, double vision, eye muscle type; upper limbs can not lift Long-lasting, take a little rest and take a rest, for the trunk type; chewing and swallowing, even respiratory muscle paralysis, for the medullary type, the most dangerous clinically is the muscle weakness crisis, the patient's respiratory muscle paralysis must be artificially assisted breathing.

At present, myasthenia gravis is considered to be an autoimmune disease. It is mainly caused by a certain mutation in the thymus. It can not control certain contraindications and allow it to differentiate and proliferate. It has an immune response to its own component (striated muscle) and muscle weakness. Myasthenia gravis has been using anti-acetylcholinesterase drugs for many years, such as pyridostigmine. In recent years, immunosuppressive agents such as hormones, cyclophosphamide, etc. have been added. The indications for surgical treatment of myasthenia gravis are accompanied or not. Patients with myasthenia gravis with thymoma, taking anti-acetylcholinesterase drugs, the dose is increasing and the symptoms are not alleviated, or the muscle weakness crisis and repeated respiratory infections.

2, simple red cell aplastic anemia (PRCA)

One of the coexisting diseases with thymoma is pure red blood cell aplastic anemia. Pure red aplastic anemia can be primary, and the cause is unclear. It can also be secondary to drugs, infections and tumors. Experimental studies have shown that PRCA is an autoimmune disease, unknown. The cause is the autoimmune response of erythrocyte antigens, which may be present in the human thymus. The thymoma itself has no direct effect on erythrocyte growth. It may be that thymoma enhances the sensitivity of the immune system, or thymoma is highly sensitive. Induced by the proliferative system.

3, nephrotic syndrome nephritis

The relationship between nephritic nephritis and thymoma is still unclear. Nephrotic syndrome can be a part of systemic manifestations of certain tumors, such as Hodgkin's disease. It may be explained by the formation of antigen-antibody complexes of thymoma and glomerulonephritis. Cross-reaction reasons.

Symptoms of thymoma Common symptoms Loss of chest pain, weakness, sternal pain, fatigue, chest tightness, low heat, repeated infection, dull pain, night sweats

Like any mediastinal tumor, the clinical symptoms of thymoma arise from the compression of surrounding organs and the symptoms characteristic of the tumor itself - the combined syndrome, small thymoma, no clinical complaints, not easy to be found, when the tumor grows to a certain volume Common symptoms are chest pain, chest tightness, cough and chest discomfort. The nature of chest pain is not characteristic, the degree is not the same, the location is not specific, generally speaking, it is light, often symptomatic, no further examination, symptom delay For a long time, some patients underwent X-ray examination, or some patients found shadows of mediastinal mass during chest examination or chest radiography. The neglected thymoma often grows to a considerable volume, and there is no vein or upper cavity. The performance of venous obstruction syndrome, severe chest pain, rapid symptoms in a short period of time, severe irritating cough, dyspnea caused by pleural effusion, pericardial effusion caused by shortness of breath, and concern about bone pain, all suggesting malignant thymoma or thymic cancer may.

The specific manifestation of thymoma is the combination of certain syndromes such as myasthenia gravis (MG), simple red cell aplastic anemia (PRCA), hypoglobulinemia, nephritic nephrotic syndrome, rheumatoid arthritis, dermatomyositis , lupus erythematosus, giant esophagus and so on.

Although thymoma can occur in all ages, most of them are between 50 and 60 years old. Children with thymoma are very rare. The incidence of thymoma is not obvious between men and women. About 50% of patients with thymoma have no obvious clinical symptoms. Most of them are detected in the chest X-ray examination. With the enlargement of the tumor or the invasion of the tumor, the patient presents with local compression symptoms, systemic reactions and symptoms associated with the disease. Patients with chest wall involvement may appear in varying degrees. Dull pain, pain in the interscapular region or sternal pain; cough, shortness of breath, chest tightness, palpitations and other symptoms of dyspnea; pressure of the recurrent laryngeal nerve may appear hoarseness, sacral nerve compression may appear diaphragmatic paralysis; upper cavity Venous obstruction manifested as facial bruising, jugular vein engorgement, such as fatigue, night sweats, low fever, weight loss, anemia, severe chest pain and pericardial effusion, pleural effusion and other signs often suggest malignant lesions or with local metastases, thymus Diseases According to Rosenow and Hurley's (1984), 40% of patients with thymoma are associated with thymus-dependent systemic or autoimmune diseases.

One third of them have two or more thymus-associated diseases, and most of these concomitant diseases are caused by autoimmune disorders, and there may be some coincidences.

1, myasthenia gravis

Myasthenia gravis is the most common disease in patients with thymoma. 30% to 70% of patients have myasthenia gravis, and 10% to 30% of patients with myasthenia gravis have thymoma. The age of onset is generally lower than that of simple myasthenia gravis. Larger 10 to 15 years old, younger than the average age of onset of thymoma, myasthenia gravis and thymoma often appear at the same time, occasionally myasthenia gravis can appear several years after the discovery of thymoma, or several days after thymoma resection Or several years, the thymoma with myasthenia gravis is more common in mixed type, followed by lymphocyte type and epithelial cell type. Spindle cell type is the least common. Thymoma may have two effects. One is to produce home immunity. The other, as an autoantibody, can inhibit the home's immune response. If the thymus of the first reaction is removed, it helps to treat myasthenia gravis, and the thymoma that suppresses the autoimmune response is removed, which causes or aggravates the severe disease. Myasthenia gravis, Kimura reported that myasthenia gravis occurred after 27 cases of thymoma resection. The prognosis of thymoma with myasthenia gravis is better than that of simple thymoma. Thymoma with myasthenia gravis and easy to early detection.

2, red blood cell dysplasia

Many patients have platelet and leukopenia at the same time, bone marrow cells and megakaryocytes are normal. The literature reports that 5% to 7% of thymoma can be associated with red blood cell dysplasia, and nearly half of patients with red blood cell dysplasia have thymoma with red blood cells. The mechanism of dysregulation is not fully understood and may be related to immunosuppression. Jepson and Vas (1974) present evidence that IgG antibodies are found in the serum of patients with thymus, IgG antibodies inhibit erythropoietin and inhibit hemoglobin synthesis, Beard (1978) Report: About 70% of the pathological types of this type of thymoma patients are non-invasive fusiform epithelial cells. After resection of the tumor, the symptoms of anemia can be significantly improved, but the prognosis is worse than that of simple thymus.

3, hypogammaglobulinemia

Clinical manifestations of recurrent infection, diarrhea, pneumonia, lymphadenitis, delayed allergic reactions, etc. Good (1954) first reported thymoma with hypogammaglobulinemia, which found that about 10% of patients with gamma globulin deficiency often combined with thymus Tumors (especially spindle-shaped epithelial thymus), Wald-man (1975) reported that such patients are more common in the elderly, mainly because of the presence of inhibitory factor T cells that inhibit gamma globulin synthesis in thymoma patients, but most The number of T cells in circulating blood of such patients is still in the normal range, and the in vitro immunological test is also in the normal range. Through clinical observation, it is considered that the removal of thymoma does not play a role in improving hypogammaglobulinemia, and the prognosis is poor.

4, systemic lupus erythematosus

Thymoma associated with systemic lupus erythematosus is rare. Maggi (1991) reported that 2.5% of 214 patients with thymoma were associated with systemic lupus erythematosus, and thymoma resection had no significant improvement in systemic lupus erythematosus. Ver- In 200 cases reported by ley (1985), 1.5% of patients with thyroid gland were found to have systemic lupus erythematosus. Clinical observations showed that thymoma resection had no effect on them, and the prognosis of such patients was poor.

5, Cushing's syndrome in addition to thymoma also seen in lung oat cell cancer, bronchial and gastric carcinoid, pancreatic cancer and thyroid-like cancer, etc., their extracts have been confirmed to contain adrenocorticotropic hormone (ACTH), some people Radioimmunoassay confirmed that the content of ACTH in epithelial cell type thymoma was quite high, and it was confirmed by electron microscopy that the tumor cells contained secretory granules.

6, tumors associated with other organs

Patients with thymoma are more likely to develop tumors in other organs than normal people. The mechanism is still unclear. Lewis (1987) summarized the follow-up data of patients with thymoma in Mayo Medical Center and found that 17% of patients with thymoma have other organs. Tumors, tumors usually occur after surgery, but before the discovery of thymoma, suggesting early thymectomy may help prevent tumors outside the thymus.

Thymoma usually presents as a anterior superior mediastinal mass that can be found during routine physical examinations of X-ray films or when symptoms are caused by their displacement of the thoracic structure, such as coughing, difficulty breathing, palpitations and substernal and interscapular Acute pain, the diversity of symptoms associated with tumors (such as myasthenia gravis, simple red blood cell dysplasia, hypogammaglobulinemia, etc.) can predict the presence of thymoma, thymoma rarely occurs in abnormal sites, such as posterior mediastinum, lung Essence and neck, ectopic phenomena are associated with defects in thymic embryo development. Myasthenia gravis is decisive for the diagnosis of thymoma. Blood system examination can also help to identify the nature of anterior mediastinal tumors. Some thymoma, due to histology The performance is not particularly typical and must be differentiated from other tumors in the anterior mediastinum, such as hemangiopericytoma, fibroblastoma, and mediastinal metastatic adenoma. Immunohistochemical staining techniques can help identify because thymoma epithelial cells have special Markers, the positive incidence rate is: cytokeratin 100%, thymosin -3 is 89%, thymosin -1 is 80%, Th-3 mouse thymus nutrition 78% of cells, 67% of Leu-7, and 60% of human thymic epithelial cells (UH-1).

1. TNM staging

According to the recommendations of Yamashiro Ishiyama in 1993, the TNM staging of thymoma epithelial cell types is:

T tumor and invasion:

The T1 naked eye capsule was intact and no microscopic infiltration was observed by microscopy.

T2 macroscopic tumor adhesion or invasion of peripheral adipose tissue or mediastinal pleura, microscopic examination of the invasion of the capsule.

T3 tumors invade surrounding organs such as pericardium, large blood vessels and lungs.

T4 pleural and pericardial spread.

N lymph node metastasis:

N, no lymph node metastasis.

N1 anterior mediastinal lymph node metastasis.

N2 anterior mediastinum and intrathoracic lymph node metastasis.

N3 supraclavicular lymph node metastasis.

M distant transfer situation:

Mo has no blood transfer.

M1 blood transfer, extrathoracic lymph node metastasis.

Phase I: T1N0M0

Phase II: T2N0M0

Phase III: T3N0M0

IV period: any T N1-3M0

Stage IVb: Any T M1

2, Haniudam et al (1992) on the basis of clinical staging, histological classification, and proposed pleural factors:

P0 represents no adhesion of the tumor to the mediastinal pleura.

P1 indicates that the tumor under the microscope has adhesion to the mediastinal pleura, but there is no invasion.

See the mediastinal pleural invasion under the P2 microscope.

3. Judging criteria for benign and malignant thymoma

The criteria for judging the benign and malignant thymoma have been different. The reasons are: 1 even if the thymoma is benign, its capsule is intact, but there is still recurrence after surgical resection. Therefore, some scholars believe that all thymoma should be considered as potential malignancy. Or low-grade malignant treatment, 2 surgery clearly found that the thymoma capsule was infiltrated or partially infiltrated into the lungs and pericardium, but postoperative pathological examination still has 5.5% to 16% of cases without tumor capsule infiltration under light microscopy And 4% to 8% of cases still have long-term survival reports, so the boundary between infiltration and non-infiltration is difficult to accurately judge in some cases.

Therefore, most scholars believe that the diagnosis of benign and malignant thymoma cannot be determined by pathological histological diagnosis alone. It must be combined with intraoperative tumor capsule infiltration, adjacent organs and pleura invading, lymph node metastasis. Comprehensive judgment, the most important morphological features of thymoma, the most important is whether the tumor capsule is intact and whether the tumor invades adjacent normal organs. Many literature reports that in all thymoma, benign thymoma is a complete non-invasive capsule. The proportion of thymoma is 40% to 70%. Occasionally, these non-invasive thymomas with intact capsules are microscopically found to have infiltrated into the capsule or capsule. Such thymoma should be classified as malignant. Invasive thymoma, thymoma with intact capsule, and even thymoma with no tumor cell infiltration under the microscope also have a lower rate of local recurrence of postoperative tumors. Therefore, even non-invasive benign thymoma is potentially malignant. Characteristics, the ratio of infiltration and growth around the thymoma is 30% to 60%, regardless of how the tumor tissue performs under the microscope or the cell structure, as long as Invasive growth of tumors should be classified as malignant tumors. In fact, in invasive thymoma, except for atypical cases of thymic epithelial cells in a few cases, most tumor cells are benign, and thymoma infiltrates into the mediastinal pleura. Pericardium, lungs, lymph nodes, large blood vessels, nerves and chest wall must be confirmed under the microscope to be definitely malignant.

A small number of thymomas appear to adhere to adjacent organs by the naked eye, but there is no malignant infiltration under the microscope. This condition should be classified as benign non-invasive thymoma. However, such thymoma is intact with the capsule and has no adhesion to adjacent organs. Compared with thymoma, its long-term survival rate is poor.

Most thymoma is infiltrated into adjacent organs, but there are also distant metastases in the thoracic cavity. Thymoma infiltrating into the diaphragm can also penetrate the diaphragm to a farther area. CT scan of the upper abdomen can help diagnose, outside the chest. Distant metastases, such as bone, liver, central nervous system, axillary and supraclavicular lymph nodes, have an incidence of 3% to 7%.

(1) Benign thymoma: The tumor capsule is intact during operation, and the postoperative pathology shows no infiltration of the subcapsular capsule and any malignant histopathological features.

(2) malignant thymoma: the tumor seen during surgery has external invasion, and there are capsule infiltration and malignant histopathological features after pathological microscopy.

Lin Zhenqiong (1992) proposed that special attention should be paid to the invasive manifestations of tumors due to inflammatory adhesions, which is considered to be as high as 21.5%, thus reminding clinicians to pay great attention to intraoperative cryosection and postoperative pathology. In order to make a more accurate judgment on the benign and malignant nature of thymoma and the comprehensive treatment and prognosis of patients.

Maggi (1991) and Kornstein (1988) also emphasized that 30% to 60% of thymoma cases, although their tumor lesions vary in size, although the tumor structure under the lens can not find a malignant basis, but as long as the microscope If the tumor is found to be based on the invasion of the adjacent structural tumor, the thymoma should be clearly diagnosed as malignant. If the surgeon believes that the tumor is invaded during the operation, the evidence of the invasion is not found under the microscope. It should be considered benign. The prognosis is not as good as the benign thymoma (ie IA stage thymoma) with no tumor invasion and intraoperative and microscopic, but the prognosis is relatively more optimistic than malignant thymoma.

4, the spread of malignant thymoma in the thoracic cavity

Local exocytosis of malignant thymoma can only be limited to the nearest organs and tissues around it, but it is clinically observed to spread to various structures in the thoracic cavity. Scatarige et al (1985) recorded 6 cases of advanced malignant thymoma in 19 cases. The diaphragm is directly invaded into the abdominal cavity. Zerhouni (1982) proposed a route of intrathoracic diffusion of malignant thymoma: the anterior lateral diffusion produces a distal implant in the pleural wall layer; the local directly invades the lung through the pleura; Direct invasion into the aortic wall and through the posterior portion of the mediastinal cavity.

Thymoma examination

There are several methods for examining this disease:

Serum acetylcholinesterase antibody (CAEab), alpha-fetoprotein (AFP) and -chorionic gonadotropin (-hCG) have certain value and specificity for the differential diagnosis of thymoma.

(1) Chest X-ray examination

X-ray examination is an important method for the diagnosis and diagnosis of mediastinal tumors. The chest radiograph is in a positive phase. The thymoma often presents a circular or elliptical dense shadow that widens or protrudes to one side of the chest cavity. On the left side, it can also be seen in the bilateral thoracic cavity. The protrusion to the left side is often covered by the aortic ball. The protrusion to the right side can overlap with the superior vena cava. The edge of the tumor is clear and sharp, and some are lobulated, lateral image. It can be seen that there is a substantial mass in the uniform density of the anterior cerebral vessels in the posterior sternum. A few thymoma can be seen in strips, spots, lumps and unformed calcification. The degree of calcification is lower than that of teratoma, and some thymoma It is flattened above the heart's large blood vessels. This type is the most difficult to diagnose in X-ray examination. Lateral lesions are a simple and economical method for determining thymoma. It can show the presence and size of tumors. Density, lateral lesions are particularly useful when unconditionally performing complex examinations.

The standard posterior anterior and lateral chest radiographs are simple and effective methods for diagnosing most thymoma. The lumps are mainly located in the anterior mediastinum or anterior superior mediastinum, and can be located in the middle of the thorax, but in most cases are biased toward one. The lateral, posterior anterior chest radiograph often shows a round, oval or shallow lobulated shape, located in the upper part of the heart shadow, close to the junction of the heart and the large blood vessels.

About 10% can appear calcification, often scattered or amorphous calcification, if the peripheral curve calcification, suggesting that the tumor is benign; irregular calcification may be benign or malignant, generally no chest radiograph Tracheal displacement, unless large invasive thymoma can cause tracheal displacement.

Lateral chest radiographs are mostly located in the anterior mediastinum, often showing a wide, narrow, narrow tongue shadow. This substantial shadow makes the anterior heart window opaque, and the edge of the shadow is often blurred and unclear, in the case of small thymoma. The lateral chest radiograph in the patient is often the only angle showing the presence of damage.

(2) chest CT examination

Chest CT is an advanced and sensitive method for examining mediastinal tumors. It can accurately show the location, size, protrusion to one side or both sides of the tumor, the edge of the tumor, the presence or absence of peripheral infiltration, and the judgment of surgical resectability. Common X-ray examination failed to diagnose the case, chest CT has its special value, CT helps to determine the scope of thymoma, not only can detect small volume (5mm or more lesions), X-ray examination is not easy to find thymoma body At the same time, through enhanced CT to show whether the mass invaded or oppressed the superior vena cava, ascending aorta, trachea, showing pericardium, chest with a small amount of fluid, with mediastinum and lungs with or without micrometastases and other X-ray films could not be displayed In general, thymoma is soft tissue density, CT value is above 40HU, after intravenous injection of contrast agent, it can be seen moderate or uniform enhancement, when the tumor is cystic, CT value is about 15HU, chest CT can be clearly The degree and extent of calcification and calcification of the tumor are shown. All patients with invasive thymoma should undergo a CT scan of the upper abdomen to detect the presence or absence of metastatic spread of the axilla.

CT: Clearly shows the relationship between the location of the tumor and the surrounding organs.

(3) Magnetic resonance imaging (MRI) For understanding the value of large blood vessel involvement, the usual MRI examination, thymoma often shows a circular, ovoid or lobulated mass in the anterior mediastinum or anterior superior mediastinum MRI is a uniform, medium-intensity MR signal region. When liquefaction necrosis occurs in the tumor, it can be expressed as an irregular high and low MR signal region. Sakai (1992) reports that MRI shows impure high-intensity and lobulated The discovery of internal structures suggests the presence of an invasive malignant thymoma.

(4) Biopsy

Including fine needle aspiration, mediastinoscopy, anterior mediastinal incision, video-assisted thoracoscopic surgery, etc., because of the large trauma of this examination, and the destruction of tumor capsule integrity, affecting the surgical effect, it is rarely used for clear diagnosis, adapt The evidence is: 1 The anterior mediastinal mass is not distinguishable from other malignant tumors in the anterior mediastinum (such as malignant lymphoma, malignant germ cell tumor, metastatic lung cancer, etc.); 2 preoperative judgment can not completely remove the tumor, must pass live Tissue examinations are performed on non-surgical complete treatment options.

Pathologically, thymoma is divided into epithelial cell type and epithelial cell lymphocyte mixture type, and it is difficult to distinguish benign or malignant thymoma from pathological morphology. According to clinical manifestations, eyesight during operation Observing what is seen and pathological features, it is more appropriate to classify invasive and non-invasive thymoma, but it is often called benign and malignant thymoma.

Diagnosis and diagnosis of thymoma

diagnosis

Diagnosis can be based on medical history, clinical symptoms, and laboratory tests.

Differential diagnosis

1, intrathoracic goiter: In addition to a few congenital vaginal thyroid, generally refers to acquired posterior sternal goiter, is caused by the neck goiter down to the anterior superior mediastinum, the characteristics of intrathoracic goiter is: 1 The majority of patients are middle-aged women; 2 the thyroid gland can be swollen and swollen, and it can move with swallowing, but because the lower pole enters the chest, it can't be smashed; 3 except for the symptoms of hyperthyroidism. Clinical symptoms, if the intrathoracic goiter is significantly enlarged, there may be varying degrees of post-sternal discomfort, difficulty breathing, wheezing during exhalation, etc. If one side is significantly enlarged, it may cause the trachea to shift to the contralateral side. 4X line appears as oval or fusiform block shadow, generally dense and uniform, the boundary is clear, even visible calcification shadow, block shadow is often located in the anterior superior mediastinum, slightly higher than the general thymoma position; 5 nuclide 131I The scan can clearly show the position in the chest; the 6-neck chest CT shows that the thyroid shadow in the neck is connected with the shadow of the chest mass, without interruption.

2, mediastinal Hodgkin's lymphoma: Hodgkin's lymphoma occurring in the mediastinum is almost nodular sclerosis, used to be called "granulomatous thymoma", currently, most scholars believe that it occurs in the thymus of Hodge In gold disease, about 90% of cases have anterior mediastinal lymph node involvement. Chest X-ray shows pre-upper mediastinal block shadow and upper mediastinal shadow is significantly widened. The characteristics of mediastinal Hodgkin's lymphoma are: 1 There are two peak phenomena, 10 to 20 years old and 50 to 70 years old, but in China, Japan and other regions are more common in middle-aged women. 2 Although nearly 50% of patients have only the symptoms and manifestations of mediastinal occupancy, More patients are often accompanied by systemic lymphadenopathy, which is more common in the neck, armpits, groin, etc. It is reported in the literature that about 70% of patients have cervical lymph node involvement, and 325% of patients are often accompanied by clinical symptoms. Such as fever, night sweats, weight loss, skin pain, 417% ~ 20% of patients after drinking alcohol 20min, localized local pain (also known as "alcohol itching"), the symptoms can be earlier than other symptoms and X-ray performance, 5 early Often accompanied by mild or moderate Anemia, a small number of patients may have mild neutrophil increase, 6CT and X-ray examination often show irregular edge of the mass, uneven density, 70% of patients in the CT examination can be found in the tracheal, hilar, subcarinal and other areas Lymph node involvement, 7 percutaneous neck, axillary lymph node biopsy is a common method for diagnosis, if necessary, through the neck incision before the mediastinum incision biopsy, 8 once diagnosed, radiotherapy plus chemotherapy is very optimistic about the effect of the disease .

3, teratoma: in addition to the gonads, the mediastinum is also a good site, most of the anterior mediastinum, especially the anterior mediastinum, only 3% to 8% in the posterior mediastinum, X-ray examination is mostly sternum The block shadow of the single hair in the back, the characteristics of teratoma are: 1 common in young adults, 2 benign teratoma generally no obvious symptoms, often found in chest X-ray examination, malignant can appear chest pain, irritation Cough, difficulty breathing, etc.; 3 If the tumor ruptures into the trachea or bronchus, you can cough up the contents of the capsule (such as sebum-like sebum, hair, teeth, etc.), if you wear a mediastinal pleura, pleural effusion occurs, if you wear a pericardium Can cause cardiac tamponade, 4 if the tumor is huge and protrude into one side of the chest, it will cause atelectasis, superior vena cava syndrome, etc., 5X line examination showed uniform density of block shadow, density of fat-containing tissue is significantly reduced Some parts of the wall may appear calcified, and even the shadow of bone or teeth may appear. 6 benign tumor markers are negative, and malignant may have different positive performances, such as AFP, LDH, CAH-S, etc. Ingredients, then S-1 00 protein is positive, if it contains leiomyosarcoma, myosin is positive. If it contains scales and adenocarcinoma, keratin is positive.

4, thymus tissue hyperplasia: can be considered as a tumor-like change of the thymus, relatively rare, mainly in adolescents, even infants and young children, its characteristics are: 1 thymic hyperplasia with its proliferative changes in morphology and location can be significantly changed, generally Often can protrude to one side of the chest or the lower mediastinum, and mistaken for mediastinal teratoma, if it is inserted into the thoracic cavity of both sides, it is often misdiagnosed as mediastinal lymphatic tuberculosis, 2 hyperplasia of the thymus compression trachea, bronchi can cause atelectasis, pneumonia, etc. , caused by fever, anemia, etc., can often be misdiagnosed as malignant lymphoma, 3 when the clinical diagnosis is suspected of thymic hyperplasia, feasible "hormone test" (oral prednisone, 1.5mg / kg per day, for 1 to 2 weeks) After 1 week of administration in most cases, the proliferating thymus begins to shrink, and the chest radiograph is reviewed. The shadow is significantly reduced, which can be diagnosed as thymic hyperplasia, thus avoiding unnecessary surgical exploration. In the early Xiangyang (1992), there were 4 cases of thymic hyperplasia in children. Three of them were misdiagnosed as mediastinal tumors or mediastinal lymphadenopathy before surgery.

Common lesions that need to be differentiated from thymoma include teratoma and ascending aortic aneurysm. Teratoma often occurs in young and middle-aged people, can be asymptomatic, or have recurrent lung infections, sometimes coughing hair or oily substances The history of the disease, X-ray examination of the mass may have teeth or bone calcification, cystic teratoma confirmed by ultrasound, the diagnosis of ascending aortic aneurysm often occurs as a thymoma, the lateral aortic aneurysm in the chest The shuttle forms a circular shadow. Along the left ventricle, the thoracic cavity shows an expansive pulsation. The auscultation can be audible and murmur. Two-dimensional ultrasonography can reveal the ascending aorta dilatation. The color Doppler can be seen in the turbulent spectrum. The chest CT image can be seen. It shows a localized tumor-like dilatation of the ascending aorta, and it is feasible to perform ascending aorta angiography when the diagnosis is difficult.

Clinically, it is also necessary to identify benign thymoma and malignant thymoma:

70% to 80% of thymoma is benign, its capsule is intact, and it is not invasive to surrounding tissues. Malignant thymoma is divided into two types: invasive thymoma and thymic carcinoma. The biological characteristics of thymoma are diseases. The treatment plan and the prognosis of the disease are of great significance. However, the benign and malignant thymoma are difficult to distinguish on the pathological tissue section, but CT can achieve satisfactory results in the observation of the growth mode of thymoma and its involvement.

1. Non-invasive thymoma CT findings

CT of thymoma showed clear tumor edge, plain scan, enhanced scan showed intact capsule, peripheral fat without infiltrating sacral shadow, no distant organ metastasis, some cases caused trachea due to large tumor, esophageal pressure shift .

2, invasive thymoma CT performance

Invasive thymoma, in addition to the mediastinal mass, also incorporates other signs of invasion:

(1) Mediastinal pleural involvement: In the CT manifestation, the tumor is irregularly thickened adjacent to the pleura, and it is uneven. However, in this group, 2 cases of intraoperative findings and postoperative pathology have pleural involvement on CT. No obvious signs were seen.

(2) The tumor is adjacent to the pericardium and the pericardial effusion is caused by planting and disseminating.

(3) pleural implants: can be expressed as a small nodular soft tissue density of the pleura, and can also be combined with unequal amount of pleural effusion.

(4) Tumor invading large blood vessels: It can be expressed as adjacent tumors such as pulmonary artery, superior vena cava, and ascending aorta in compression and deformation. When the scan is enhanced, the vessel wall is invaded.

(5) The chest cavity is invaded as pleural effusion.

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