CHAPTER 11



CHAPTER 11SARCOIDOSIS11.1. EtiologyDespite advances in the immunology of sarcoidosis, the etiology of this disease remains unknown. Various studies examining T cell receptor expression on lymphocytes isolated from the lungs of patients with sarcoidosis support an immunologic reaction to a single agent. Potential antigens that have been implicated in stimulating this disease include both exogenous agents, such as infections (mycobacteria, Yersinia enterocolitica, viruses, fungi) and respirable particles (inhaled organic or inorganic antigens), as well as endogenous agents, such as latent viral or tumor antigens. No evidence, however, indicates that any of these agents is the cause of sarcoidosis. Sarcoidosis has also been shown to occur in some families and in some identical twins, suggesting that genetic factors also play a role in expression of this disease.Sarcoidosis is a multisystem disorder of unknown etiology characterized pathologically by the presence of epithelioid granulomas.11.2. PathologyThe epithelial granuloma is the pathologic hallmark of sarcoidosis. The epithelioid granuloma contains two zones: a central compact zone consisting of mature mononuclear phagocytes, epithelioid cells, and giant cells mixed with lymphocytes of the CD4+ type and a peripheral zone consisting of macrophages, monocytes, fibroblasts, and lymphocytes, which, in addition to the CD4+ type, are also of the CD8+ type. Morphologically, both the mononuclear phagocytes and the lymphocytes appear activated. In the lung, granulomas are primarily localized to areas that parallel lymphatic drainage, including the peribronchial and mediastinal lymph nodes, pleural tissue septa and along blood vessels.11.3. PathogenesisSarcoidosis results from the immunologic persistence of activated monocytes (macrophages) and activated CD4+ lymphocytes at sites of disease. The activated mononuclear cells can affect the host by regulating the initiation, maintenance, and resolution of local granuloma formation and by releasing a variety of mediators that potentially have systemic effects on the host (interleukin 1 [IL-1], tumor necrosis factor [TNF], interleukin 8 [IL-8]). The precursor to granuloma formation in sarcoidosis is alveolitis. In the lung this inflammatory process is localized to the interstitium and is reflected in the cells recovered by bronchoalveolar lavage. In normal people, alveolar macrophages make up greater than 85% of the cells, whereas lymphocytes constitute less than 15% of the cells, and both lymphocytes and macrophages are not activated. In contrast, patients with sarcoidosis have greater numbers of both macrophages and lymphocytes in bronchoalveolar lavage, with lymphocytes constituting a much larger percentage of the cells. The lymphocytes recovered are predominantly T helper cells. Activated sarcoid macrophages and lymphocytes may participate in the fibrotic process by releasing mediators that can up-regulate fibroblast proliferation and collagen release.In sarcoidosis, granuloma formation is often confined to specific sites of disease activity. For example, although both macrophages and T helper lymphocytes are increased in number and activated in the lungs of patients with sarcoidosis, these same patients often have a reduction in the circulating number of T helper cells. 11.4. Clinical findingsWorldwide in distribution, sarcoidosis has a predilection for temperate environments. It is common in Sweden but occurs very infrequently in Africa, Southeast Asia, and the Hawaiian Islands. Sarcoidosis can occur in any age and race; however, it appears to be found more frequently in younger people (more than 70% of cases in people under 40 years of age), blacks, and within the black race, females. Sarcoidosis can be asymptomatic; 80% of patients with sarcoidosis in a New York study had no symptoms. Also, a chest radiographic screening of the population in Denmark detected fourfold more patients with sarcoidosis than did studies for patients who had symptoms.Sarcoidosis can affect any organ of the body. The disease can present acutely, subacutely, or chronically and can affect a single organ, or multiple organs (table 26). The patient's ethnic background has been demonstrated to influence the mode of presentation, organ involvement, and clinical course in sarcoidosis. For example, Swedish and Irish women often have Loeffler's syndrome, an acute disorder manifested by erythema nodosum, polyarthritis, iritis and fever that has a good prognosis. In contrast, West Indian people have a later onset of disease and multiple organ involvement, including the respiratory, ocular, and reticuloendothelial systems. It seems that genotype may influence disease expression. Human leukocyte antigen B8 (HLA-B8), for example, has been associated with erythema nodosum, arthritis, and early resolution.Fatigue, weakness, malaise, weight loss, anorexia, fever and sweats are some of the most common symptoms at presentation in sarcoidosis. Sarcoidosis can determine intrathoracic and extrathoracic involvement. Generally regarded as benign, sarcoidosis can also involve a number of vital structures, including those in the respiratory, cardiac, endocrine, ophthalmologic, and central nervous systems, with potential life-threatening implications.Table 26 - Organ system involvement in sarcoidosisOrgan systemClinical incidenceThoracic Pulmonary Hilar nodes Parenchima Cardiac90-95%75%50%5-10%Extrathoracic Erythema nodosum Hypercalcemia Hypercalciuria Gastrointestinal Musculoskeletal Nervous system Ophtalmologic Liver Lymph nodes Upper respiratory15-20%2-5%20-50%1-2%10-20%3-5%20-50%20%20%5-15%11.4.1. Intrathoracic sarcoidosis? The respiratory system is the most frequently involved organ system. Up to 90% of patients with sarcoidosis have pulmonary involvement at some time during the course of their disease. Of these, 60% may develop symptoms of cough, wheezing, or dyspnea. Intrathoracic lymph nodes are enlarged in 75-90% of patients. The hilar nodes are usually involved and less frequently the mediastinal nodes. Chest radiographs are grouped into the following stages: stage 0, normal; stage I, bilateral hilar adenopathy (figure 55); stage II, bilateral hilar adenopathy with diffuse parenchymal infiltrates; stage III, diffuse parenchymal infiltrates without bilateral hilar adenopathy. Progressive pulmonary sarcoidosis occurs in up to 20% of patients. The resultant physiologic abnormalities are those seen in most restrictive diseases. Some patients may also have an added obstructive component resulting from endobronchial disease. Exercise testing may be useful in delineating the pulmonary or extrapulmonary (cardiac disease, anemia, myopathy) cause of dyspnea in patients with sarcoidosis. Briefly, although pulmonary function tests do not always correlate with the symptoms and radiographic stage of sarcoidosis, they appear to be a sensitive way to follow the course of disease. The upper airway can also be involved with sarcoidosis, including the nasopharynx, larynx, vocal cords, paranasal sinuses, and nasal bones. Figure 55 - Stage I sarcoidosisThis radipograph shows bilateral hilar node enlargement. The “tongue” of normal lung between the hilar node enlargement and the cardiac outline is often observed in sarcoidosis.The stages demonstrated on chest radiographs can not anticipate the progression of the underlying disease, but can predict the resolution of infiltrates (table 27).Table 27 - Radiographic stage of sarcoidosis and prognosisStageResolutionProgressionIIIIII54%31%4%7%13%10%? Cardiac sarcoidosis, although infrequent, is important because it can be potentially lethal and a major source of symptoms, including dyspnea and cough, without clinical evidence of disease elsewhere. Similar to that of the lung, granulomatous involvement of the heart is patchy. The degree of cardiac compromise depends not only on the extent but also on the location of the disease. Granulomas localized to the conduction system potentially can result in heart block or arrhythmias. Likewise, extensive myocardial involvement may cause a restrictive and dilated cardiomyopathy. The mortality from cardiac sarcoidosis approaches 20% to 30%. Severe pulmonary disease also causes secondary cor pulmonale. In addition to direct cardiac involvement, the heart's electrical system also may be altered by hypercalcemia. 11.4.2. Extrathoracic sarcoidosis ? The mechanism for both the hypercalcemia and the hypercalciuria in sarcoidosis is an increase in 1,25-dihydroxycholecalciferol concentration which results in an increase in intestinal calcium absorption. In addition, chronic renal insufficiency from nephrolithiasis and nephrocalcinosis may be the result of a persistent hypercalcemia.? Ocular sarcoidosis, often clinically asymptomatic, can result in blindness. The most common structure involved is the anterior uveal tract. Involvement of any of the ocular structures, however, has been described. Although a careful eye history (altered visual acuity, watering, redness, photophobia) and examination are important, sarcoid eye disease is often asymptomatic and can only be detected by slit-lamp examination. ? Sarcoidosis can involve any portion of the nervous system, including the cranial nerves (most often VII), the peripheral nerves, the skeletal muscle, the basal meninges, and the central nervous system in the form of inflammation or mass lesions. Lesions are more frequently localized at the base of the brain and, if localized to the hypothalamic/ pituitary region, may result in diabetes insipidus or galactorrhea /amenorrhea. Seizures are a marker of severe central nervous system disease. Cerebrospinal fluid is typically lymphocytic with an elevated protein concentration. ? In sarcoidosis, the liver may be enlarged, but severe hepatic dysfunction with esophagogastric variceal formation is unusual. Splenic enlargement may result in pancytopenia.? Skin manifestations from sarcoidosis can be the result of direct granulomatous involvement of the tissue (lupus pernio, skin plaques, cutaneous nodules) or the result of a vasculitic response. The latter is the mechanism responsible for erythema nodosum in these patients. Lupus pernio is a chronic violaceous lesion of the face that, in contrast to erythema nodosum, has been associated with multiple organ involvement, laryngeal sarcoidosis, and a poor prognosis.? Sarcoidosis can also affect the skeletal, gastrointestinal and urinary systems. Involvement of the parotid or lacrimal glands in combination with uveitis and fever has been termed uveoparotid fever or Heerfordt's syndrome.? Peripheral lymphadenopathy is common, involving the cervical, axillary, epitrochlear and inguinal nodes. These nodes are nonadherent and have a firm, rubbery texture; palpation causes no pain and the nodes do not ulcerate.11.5. LABORATORY FINDINGS Blood tests in sarcoidosis show lymphocytopenia, increased erythrocyte sedimentation rate, hyperglobulinemia and high level of angiotensin-converting enzyme; hypercalcemia is rare. Angiotensin-converting enzyme (ACE) levels are elevated in 40-80% of patients with active sarcoidosis (its synthesis is controlled by T lymphocytes). This finding is neither sensitive nor specific enough to have diagnostic significance.. The chest x-ray is abnormal in almost all cases, showing bilateral hilar adenopathy, associated or not with diffuse parenchymal changes (reticulonodular infiltrates). The three radiographic patterns of sarcoidosis – already described in the previous chapter – are not consecutive stages of the disease and do not represent evolutive criteria for sarcoidosis. Focal infiltrates, acinar shadows, nodules, and, rarely, cavitation may be seen. Pleural effusion is noted in fewer than 10% of patients. The lung function tests show restriction, with decreased lung volumes and normal forced expiratory volume in one second (FEV1), typical aspect for interstitial lung disease. The diffusing capacity is also decreased. Endoscopy with transbronchial biopsy and bronchoalveolar lavage is the procedure of choice in patients with suspected pulmonary involvement. Bronchoalveolar lavage fluid in sarcoidosis is usually characterized by an increase in lymphocytes and a high CD4/CD8 cell ratio. Skin test anergy (including tuberculin skin test) is present in 70% of patients with sarcoidosis.11.6. DIAGNOSISThe diagnosis of sarcoidosis is made on the basis of the history, radiographic and pathologic findings. It generally requires histologic demonstration of noncaseating granulomas in biopsies from a patient with other typical associated manifestations. Other granulomatous diseases (especially tuberculosis) must be ruled out. If indicated, biopsy of easily accessible sites, like palpable lymph nodes, skin lesions, or salivary glands, is likely to provide positive findings. Transbronchial lung biopsy has a high rate of positive findings, especially in patients with radiographic evidence of parenchymal involvement. Biopsy is essential whenever clinical and radiographic findings suggest the possibility of an alternative diagnosis such as lymphoma. Patients with suspected myocardial or central nervous system sarcoidosis have a potentially life-threatening disease that requires specific therapy. Gallium-67 scanning may be helpful in selecting the tissue to biopsy. The Kveim test has been used to confirm the diagnosis of sarcoidosis; the 4- to 6-week delay before test interpretation, the 20% false-negative rate, the number of false-positive results, and the lack of a commercially available reagent make this test impractical for routine use. Angiotensin converting enzyme (ACE) is elevated in up to 80% of patients with sarcoidosis because of the ongoing production of the enzyme by epithelioid cells in the granulomas; it is not specific for sarcoidosis and can be elevated in a variety of disorders. ACE serum levels usually fall with clinical improvement.11.7. DIFFERENTIAL DIAGNOSISSarcoidosis has to be differentiated from other lung diseases manifested by similar radiographic elements: hilar and mediastinal lymph nodes enlargement and parenchimal reticulonodular pattern (diffuse fibrosis). In the differential diagnosis of sarcoidosis the following diseases will be considered:Infectious diseases – Bacteria Mycobacteria - M. tuberculosis- Atypical mycobacteria Brucella Francisella tularensis Yersinia enterocolitica- Fungi Histoplasma capsulatum Coccidioidis immitisNoninfectious diseases hypersensitivity pneumonitis inorganic dusts - talc, beryllium drugs – methotrexate neoplasms – lymphoma, mediastinal tumors Wegener`s granulomatosis11.8. PROGNOSISPulmonary sarcoidosis is usually a self-limited condition, with about 50% of patients showing some improvement and 25% remaining unchanged. The reversible lesion in the lung is the alveolitis, whereas the fibrosis is irreversible. About 20% of patients with lung involvement suffer irreversible lung impairment, characterized by progressive fibrosis, bronchiectasis and cavitation. Pneumothorax, hemoptysis, mycetoma formation in lung cavities and respiratory failure often complicate this advanced stage of sarcoidosis. Myocardial sarcoidosis occurs in about 5% of patients, sometimes leading to cardiomyopathy, cardiac arrhythmias and conduction disturbances. Up to 10% of patients may die from sarcoidosis. In general, patients with multiple organ involvement, a slower onset of disease, and a more advanced stage on chest radiography have a worse prognosis. The prognosis is best for patients with hilar adenopathy alone. 11.9. TREATMENT Individualizing therapeutic regimens is particularly important in patients with sarcoidosis because the disease has a heterogeneous presentation and course. Most patients, because of the disease's self-limited nature, do not require therapy but rather simple observation. Anti-inflammatory therapy is indicated for individuals who have either severe or progressive disease. To determine if progressive disease is present, individuals initially with apparently benign disease should be followed at least at 6-month intervals to observe for evidence of progressive disease. Serial pulmonary function testing is particularly useful in this regard. Some patients must be treated immediately. These patients usually have critical organ involvement (cardiac disease, central nervous system disease, ocular disease, persistent hypercalcemia or hypercalciuria) or disfiguring skin lesions. Many patients with pulmonary disease need to be treated immediately if progressive pulmonary functional impairment is already evident. Glucocorticoids are currently the principal anti-inflammatory agents used: prednisone (1 mg/kg/day) for 4 to 6 weeks, with a rapid tapering (0.25 mg/kg/day) for 3 months more. The prednisone is then tapered to an alternate-day regimen to reduce systemic side effects or to as low a dosage as the patient tolerates. If disease progresses despite prednisone therapy, disease recurs after tapering the prednisone, or severe glucocorticoid-related side effects occur, we institute alternative anti-inflammatory therapy with alternative anti-inflammatory agents: methotrexate, cyclophosphamide or cyclosporine.CHAPTER 14MEDIASTINAL SYNDROMES14.1. ANATOMY AND PHYSIOLOGYThe mediastinum comprises the part of the thorax that lies between the lungs. The mediastinum is bounded superiorly by the thoracic inlet, anteriorly by the sternum, laterally by the parietal pleura, inferiorly by the diaphragm, and posteriorly by the spine and ribs. Within the mediastinum lie the heart and central vessels, the major airways, the esophagus, phrenic nerves, vagus nerves, sympathetic trunks, lymph nodes, and the main channel of the lymphatic system. All these structures can be affected primarily or secondarily by diseases involving the mediastinum.Classically the mediastinum is divided into three compartments: anterior, middle and posterior mediastinum. The contents of each compartment are listed below (table 29).Table 29 - Contents of mediastinal compartmentsAnterior or anteroposteriorThymus glandAortic arch and major branchesInnominate veinsLymphatic and areolar tissueThyroid gland (occasionally)Upper trachea and upper esophagusMiddleHeartPericardiumTracheaHilum of each lungTracheobronchial lymph nodesPhrenic nervesPosteriorEsophagusVagus nervesSympathetic nerve chainsThoracic ductDescending aortaAzygos and hemiazygos venous systemsParavertebral lymph nodes The differential diagnosis of an anterior mediastinal mass includes thymoma, teratoma (figure 59), thyroid lesions, lymphoma and mesenchymal tumors (lipoma, fibroma). Figure 59 - Anterior mediastinal tumour: dermoid cyst.A smooth, clearly defined opacity is superposed on the shadow of the left hilum The differential diagnosis of a middle mediastinal mass includes lymphadenopathy, pulmonary artery enlargement, aneurysm of the aorta, developmental cyst (bronchogenic, pleuropericardial), dilated azygous vein and foramen of Morgagni hernia. The differential diagnosis of a posterior mediastinal mass includes hiatus hernia, neurogenic tumor (neurofibroma, neurosarcoma, ganglioneuroma, pheochromocytoma) meningocele, esophageal tumor, foramen of Bochdalek hernia.14.2. CLINICAL FINDINGSSymptoms and signs of mediastinal masses are nonspecific and are usually caused by the effects of the mass on surrounding structures. In adults, almost 50% of mediastinal masses are asymptomatic. In children, mediastinal lesions are more likely to cause symptoms and findings. About 50% of symptomatic mediastinal masses prove to be malignant, whereas about 90% of asymptomatic masses are benign. The most frequent symptoms are chest pain, cough, dyspnea, hoarseness, recurrent respiratory infection, and dysphagia, all usually resulting from compression by a mediastinal lesion or invasion of adjacent structures. Less frequent local symptoms include superior vena caval obstruction, vocal cord paralysis, Claude Bernard - Horner syndrome and spinal cord compression. The presence of cough, hemoptysis, or stridor with a mediastinal mass suggests malignancy; hemoptysis is particularly suggestive of a bronchogenic carcinoma. Inspiratory stridor may occur with narrowing of the extrathoracic trachea or bilateral vocal cord paralysis and is a threatening sign. Usually, tumors grow to a large size before pain develops, but retrosternal pain suggests malignancy or inflammatory disease. Dyspnea may be caused by compression of the major airways, involvement of the phrenic nerve paralyzing diaphragmatic function, or a concomitant pleural effusion (table 30).Table 30 - Symptoms of mediastinal massesCoughHemoptysisStridorDyspnea, especially with phrenic nerve palsyHoarseness (vocal cord paralysis)Superior vena caval obstructionPain (usually retrosternal)DysphagiaPleural effusion, including chylothoraxSpinal cord compressionPericarditis and pericardial tamponadeHorner's syndrome Some patients have systemic symptoms resulting from endocrine secretion by the tumor, such as manifestations of hyperthyroidism caused by intrathoracic thyroid adenoma, hypercalcemia secondary to parathyroid adenoma, and systemic hypertension in association with neurogenic tumor. Myasthenia gravis occurs with thymoma, and fever occurs with Hodgkin's disease (table 31).Table 31 - Systemic syndromes associated with mediastinal tumorsTumorSyndromeThymomaMyasthenia gravis, red cell aplasia, hypogammaglobulinemia, Cushing's syndromeGerm cell tumorGynecomastiaSubsternal goiterThyrotoxicosisLymphoma (Hodgkin's disease)Fever of undetermined origin, hypercalcemiaNeurofibromaOsteoarthropathyPheochromocytomaHypertensionGanglioneuromaHypertension, diarrheaParathyroid adenomaHypercalcemia14.2.1. Superior vena caval obstructionObstruction of the superior vena cava produces a characteristic syndrome that often appears abruptly with headache, swelling, and venous engorgement of the face, chest and arms. Patients with superior vena caval obstruction have distended, nonpulsatile jugular veins and often prominent upper thoracic collateral venous circulation. Obstruction below the junction of the azygos vein usually produces greater obstructive symptoms and results in extensive collateral routes through the abdominal wall to enter the drainage system of the inferior vena cava. Conjunctival edema and even chemosis can occur when obstruction has been rapid in onset.CausesIn patients with a history of smoking, especially middle-aged males, the diagnosis is almost always bronchogenic carcinoma. Attempts to confirm the diagnosis histologically must be undertaken with care because of the risks of bleeding. Sputum cytology may be helpful. If cytology is negative, bronchoscopy must be performed. Evidence of disease elsewhere, such as in lymph nodes, should be sought because scalene lymph node biopsy or mediastinoscopy may be accompanied by bleeding. However, fine-needle aspiration of supraclavicular nodes or of a mediastinal mass is safe in these patients. In younger patients, in patients with bilateral hilar masses, or in those with lymphoma elsewhere, it is important to establish a histologic diagnosis because therapy depends on it. In such patients, more material for histology is necessary than can be obtained by fine-needle aspiration, and tissue from extrathoracic sites should be sought. TreatmentOnce the diagnosis of caval obstruction has been established, treatment is determined by the nature of the primary disease. Symptomatic therapy includes diuretics and corticosteroids. Emergency treatment with chemotherapy or radiotherapy is often indicated for this condition. Whatever form of therapy is used, relief of obstructive symptoms is usually satisfactory because collateral vessels develop, even in the absence of resolution of the caval obstruction. Surgical relief of caval obstruction in patients with nonmalignant disease has been tried with occasional success, but generally surgical procedures offer little therapeutic help. 14.2.2. HoarsenessHoarseness associated with a mediastinal mass usually results from paralysis of the left recurrent laryngeal nerve. This paralysis is most often associated with malignancy but is occasionally caused by an aortic aneurysm.14.2.3. Claude Bernard - Horner syndromeTumors of the anterior mediastinum may produce involvement of the cervical or thoracic sympathetic ganglia, resulting in Claude Bernard-Horner syndrome (unilateral palpebral ptosis, enophthalmos, constricted pupil, warmth and dryness of the face on the affected side). The most common cause of Horner's syndrome is bronchogenic carcinoma.14.3. LABORATORY FINDINGSDiagnostic studies have the purpose of localizing the lesion, determining its site of origin, and obtaining a tissue diagnosis. The investigation of mediastinal lesions should follow a sequence from simpler, inexpensive techniques to complex, expensive and less comfortable techniques. Since localization is of major importance, radiographic techniques play a crucial role. A good chest film, particularly the lateral view, is the initial diagnostic test, providing information on the size and location of the mass. Computed tomography (CT) is most valuable because masses of different density can be identified, fatty tissue and cysts can be differentiated. With the use of contrast materials, vascular lesions can be distinguished from nonvascular structures. CT is used to assess mediastinal lymphadenopathy and is particularly valuable in the posterior mediastinum. A barium contrast study of the esophagus may distinguish intrinsic pathology from extrinsic compression or may demonstrate a fistula. Magnetic resonance imaging (MRI) may be used to complement a CT scan. Its advantages include distinction between vessels and masses, no need for contrast media, and better delineation of hilar structures. MRI also allows imaging in multiple planes, whereas CT permits only axial imaging. angiography, Doppler sonography, venography of brachiocephalic veins and the superior vena cava for suspected vascular lesions. thyroid scintigraphy is used in diagnosing thyroid tumors. Nonvascular masses usually require a histologic diagnosis; several techniques are available for obtaining tissue. In the appropriate setting, not only may bronchoscopy and esophagoscopy reveal compression, but a biopsy may also be obtained. Transthoracic fine-needle aspiration for cytology is also a useful technique. Mediastinoscopy is performed through an incision just above the sternal notch and is a valuable procedure for obtaining adequate amounts of tissue for specific diagnosis. Only lesions in the upper anterior mediastinum can be explored by this technique. Lesions beyond the reach of the mediastinoscope can be approached by anterior mediastinotomy. 14.4. SPECIFIC DISEASES14.4.1. TumorsThe location of mediastinal tumors is important in diagnosis because of the predilection of mediastinal lesions to arise in specific compartments (table 32). Anterior mediastinal tumors Thymoma is the most common tumor originating in the anterior mediastinum. Benign and malignant thymomas are distinguished by their invasive features rather than by their microscopic appearance. About 30% of thymic tumors are malignant and invade locally rather than by hematogeneous spread. Approximately 70% of thymomas are associated with systemic symptoms, of which the most common is myasthenia gravis, associated with up to 50% of thymomas; conversely, 10% to 15% of patients with myasthenia have a thymoma. The treatment of choice for a thymoma is surgical removal. A patient with myasthenia has a significant chance of improvement. Malignant thymomas may respond to radiation therapy, occasionally used in conjunction with surgery. Germ cell tumors of the mediastinum occur in adolescents or young adults and are classified into benign teratomas, malignant teratomas and seminomas. About 20% of these tumors are malignant and occur more frequently in males. The cystic teratomas, or dermoids, are usually benign, whereas almost one third of solid tumors are malignant. Benign teratomas may be identified because calcification, hair, or teeth are found within the cyst. Benign teratomas are usually easily resected, but complete removal of malignant teratomas may be impossible. Seminoma is the most common form of malignant germ cell tumor to affect the mediastinum primarily and the anterior compartment exclusively. Treatment of patients with seminoma should include surgical extirpation and radiation therapy Table 32 - Classification of mediastinal massesAnterior or anterosuperiorThymomaGerm cell tumorLymphomaSubsternal goiterEnlarged fat pad or lipomaAneurysm of ascending aortaParathyroid adenomaMiddleBronchogenic carcinomaBronchogenic cystLymphomaMetastatic tumorSystemic granuloma (sarcoid, histoplasmosis, tuberculosis)Pericardial cystPosteriorNeurogenic tumorBronchogenic cystEnteric cystAneurysm of descending aortaDiaphragmatic herniaParavertebral abscessMeningoceleAchalasia Substernal goiters are an important cause of anterior mediastinal masses. The routine chest film is occasionally diagnostic, with evidence of displacement and/or compression of the trachea, a smooth outline, and some calcification within the mass. CT is often most helpful, demonstrating continuity of the mass with the cervical thyroid and confirming calcification. Surgical excision is the treatment of choice. Aneurysms of the ascending aorta, now usually arteriosclerotic in origin, usually present as anterior mediastinal masses. Angiography is often required to define the full extent of the aneurysm and assess the feasibility of surgery. Patients with spontaneous or iatrogenic Cushing's syndrome often have radiographic evidence of fullness of the anterior mediastinum, best visualized on the lateral chest film, caused by an enlarged mediastinal fat pad and no therapy is indicated. CT is particularly useful in identifying fatty tissue in these patients or when a lipoma is present. Lymphomas may present as anterior mediastinal masses (figure 60). Diagnosis must be confirmed histologically. Fibromas, hemangiomas and lymphangiomas are rare, benign masses that require surgical excision to confirm the diagnosis.Figure 60 - Anterior mediastinal tumour: lymphomaMiddle mediastinal tumors Lymph node enlargement is a common cause of a mass in the middle mediastinum, most often caused by malignancies, either lymphoma or metastatic carcinoma (figure 61). Small cell carcinoma of the lung may also present as a middle mediastinal mass, with a central bronchial tumor and mediastinal lymph node involvement. Figure 61 - Mediastinal metastatic tumourThe left hilum is enlarged by a round mass which was proved to be a metastases from a stomach tumour.Benign disorders involving mediastinal nodes include sarcoidosis, histoplasmosis, coccidioidomycosis, and primary tuberculosis. Congenital cysts account for about 20% of mediastinal masses. Most are discovered incidentally on routine chest radiographs in asymptomatic individuals and are confirmed to be cystic on a CT scan.- Pericardial cysts are the most common congenital cysts of the mediastinum. They are usually solitary and are seen in the right cardiophrenic angle. CT and ultrasonography are useful in the diagnosis. Surgical excision is usually performed.- Bronchogenic cysts occur in the lung or mediastinum. In the adult they are usually asymptomatic, whereas in children they may cause tracheobronchial compression with cough, stridor, wheezing, dyspnea and occasionally atelectasis. Cysts sometimes become infected and produce a mediastinal abscess. Surgical removal of the cyst is indicated. Posterior mediastinal tumors Neurogenic tumors, the most common posterior mediastinal tumors, include all benign and malignant masses arising from the intercostal nerves, sympathetic ganglia, and chemoreceptor cells. In adults, most are asymptomatic and benign, whereas in children, 50% are symptomatic and malignant. The neural tumors are differentiated in neurofibroma, ganglioneuroma, neuroblastoma, pheochromocytoma. Radiographically, neurogenic tumors are rounded, homogeneous and well circumscribed and are seen in the paravertebral sulcus. About one third of these neural tumors become malignant; therefore all should be excised.14.4.2. PneumomediastinumPneumomediastinum is the presence of gas in the interstices of the mediastinum. It can occur spontaneously, from trauma, or from dissection of air from the neck or retroperitoneal space. Spontaneous pneumomediastinum In the absence of an obvious cause, pneumomediastinum is said to be spontaneous. Air leaks from alveoli into the interstitium of the lung and then into the perivascular sheaths, the hilar regions, and subsequently the mediastinum. The condition may be precipitated by a sudden rise in intrathoracic pressure during coughing or after a Valsalva maneuver.In adults, this condition can occur in young, otherwise healthy individuals, or it may be associated with asthma, pneumonia, bronchitis, emphysema or pulmonary fibrosis and it may be a complication of positive-pressure ventilator therapy. The air may spread from the mediastinum to the subcutaneous tissues of the neck or axilla, producing subcutaneous emphysema; and it may leak into the pleural space, producing pneumothorax.Patients with spontaneous pneumomediastinum may be asymptomatic or have retrosternal chest pain and dyspnea. The diagnosis is usually made by radiography. A thin line of air is seen along the border of the mediastinum; sometimes this line of air is more clearly seen on the lateral chest film. Most patients with spontaneous pneumomediastinum do not require specific therapy but, if occasionally severe symptoms develop, decompression is indicated by either needle aspiration or mediastinotomy. Traumatic pneumomediastinum is most commonly caused by the rupture of esophagus, which can occur during an episode of severe vomiting or rarely, after esophageal instrumentation. Rupture of the esophagus is usually associated with severe, chest pain and may be complicated by acute mediastinitis. Traumatic pneumomediastinum can also occur after penetrating wounds of the chest or after fracture of the trachea or main bronchus after a trauma to the chest. Traumatic pneumomediastinum requires thoracotomy, with repair of the esophagus or tracheobronchial tree. 14.4.3. Mediastinitis Acute mediastinitis is usually the result of introduction of germs into the mediastinum after perforation of the esophagus. The diagnosis should be suspected when substernal pain, fever and radiographic evidence of mediastinal air develop after a bout of vomiting or instrumentation. This setting represents an emergency requiring antibiotic therapy directed at gram-positive, gram-negative, and anaerobic organisms as well as early surgical drainage and repair. Chronic mediastinitis is a condition of unknown cause that produces fibrosis in the mediastinum, with compression and restriction of vascular structures entering and leaving the mediastinum. It was previously thought that tuberculosis was the chief cause of chronic fibrosing mediastinitis, but other granulomatous diseases, particularly histoplasmosis, may also cause this syndrome. The initial infection may precede the chronic condition by months or years. Symptoms are nonspecific and include chest pain, superior vena caval obstruction and bronchial obstruction with distal infection and cough. Full evaluation of the patient includes bronchoscopy and ventilation-perfusion lung scans, in addition to skin testing for tuberculosis. Treatment is very limited once vascular obstruction has developed. ................
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