2Pathologic involvement of the pleura; most often, a secondary complication of some underlying diseasecommon pleural findings at autopsySecondary infections and pleural adhesionsImportant primary disorders include;(1) primary intrapleural bacterial infectionsimply seeding of this space as an isolated focus in the course of a transient bacteremia(2) a primary neoplasm of the pleura:mesothelioma
3Pleural effusion;common manifestation of both primary and secondary pleural diseasesmay be inflammatory or noninflammatoryNormally,no more than 15 mL of serous,relatively acellular,clear fluid lubricates the pleural surface.Accumulation of pleural fluid occurs in the following settings: Increased hydrostatic pressure, as in congestive heart failure Increased vascular permeability, as in pneumonia Decreased osmotic pressure, as in nephrotic syndrome Increased intrapleural negative pressure, as in atelectasis Decreased lymphatic drainage, as in mediastinal carcinomatosis
4Inflammatory pleural effusions Serous, serofibrinous, and fibrinous pleuritisall are caused by essentially the same processes.Fibrinous exudationsgenerally reflect a later, more severe exudative reactionmight have presented as a serous or serofibrinous exudate, in an earlier developmental phaseCommon causes of pleuritis are inflammatory diseases within the lungs;tuberculosispneumonialung infarctslung abscessbronchiectasis
5Serous or serofibrinous pleuritis Rheumatoid arthritisdisseminated lupus erythematosusuremiadiffuse systemic infections, other systemic disordersmetastatic involvement of the pleura can also cause.Serofibrinous pleuritisRadiation therapy for tumors in the lung or mediastinumMostly the serofibrinous reaction is only minimalfluid exudate is resorbed with either resolution or organization of the fibrinous component.Accumulation of large amounts of fluid can sufficiently encroach on lung space to cause respiratory distress
6EmpyemaA purulent pleural exudate usually results from bacterial or mycotic seeding of the pleural spaceMostlyseeding occurs by contiguous spread of organisms from intrapulmonary infection, butOccasionallyoccurs through lymphatic or hematogenous dissemination from a more distant sourceRarely,infections below the diaphragm,subdiaphragmatic or liver abscess,may extend by continuity through the diaphragm into the pleural spaces,more often on the right side.
7Empyema characterized by loculated, yellow-green, creamy pus composed of masses of neutrophils admixed with other leukocytesmay accumulate in large volumes (up to 500 to 1000 mL),usually the volume is small, and the pus becomes localizedEmpyema may resolve,but this outcome is less commonOrganization of the exudate,with the formation of dense, tough fibrous adhesionsfrequently obliterate the pleural space or envelop the lungs;either can seriously restrict pulmonary expansion
8True hemorrhagic pleuritis manifested by sanguineous inflammatory exudates isinfrequentFound in hemorrhagic diatheses, rickettsial diseases, and neoplastic involvement of the pleural cavityThe sanguineous exudate must be differentiated from hemothoraxWhen hemorrhagic pleuritis is encountered,careful search should be made for the presence of exfoliated tumor cells
9HydrothoraxNoninflammatory collections of serous fluid within the pleural cavitiesThe fluid is clear and straw coloredmay be unilateral or bilateral,depending on the underlying causemost common cause;cardiac failure,usually accompanied by pulmonary congestion and edema.Transudates may collect in any other systemic disease associated with generalized edemafound in renal failure and cirrhosis of the liver.
10Hemothorax Chylothorax escape of blood into the pleural cavity almost invariably a fatal complication of a ruptured aortic aneurysm or vascular traumamay occur post-operatively.Pure hemothorax is readily identifiable by the large clots that accompany the fluid component of the bloodChylothoraxaccumulation of milky fluid, usually of lymphatic origin, in the pleural cavity.Chyle is milky whitebecause it contains finely emulsified fatsmost often caused by;thoracic duct traumaobstruction that secondarily causes rupture of major lymphatic ductsmalignant conditions within the thoracic cavity that cause obstruction of the major lymphatic ducts.More distant cancers may metastasize via the lymphatics and grow within the right lymphatic or thoracic duct to produce obstruction.
11Pneumothorax air or gas in the pleural cavities may be spontaneous, traumatic, or therapeuticSpontaneous pneumothorax may complicate any form of pulmonary disease that causes rupture of an alveolusAn abscess cavity that communicates either directly with the pleural space or with the lung interstitial tissue may also lead to the escape of air. In the latter circumstance the air may dissect through the lung substance or back through the mediastinum (interstitial emphysema), eventually entering the pleural cavityPneumothorax is most commonly associated with;emphysema,asthma,tuberculosisTraumatic pneumothoraxusually caused by some perforating injury to the chest wall,but sometimes the trauma pierces the lung and thus provides two avenues for the accumulation of air within the pleural spacesResorption of the pleural space air occurs slowly in spontaneous and traumatic pneumothorax,provided that the original communication seals itself
12One that attracts greatest clinical attention is spontaneous idiopathic pneumothorax encountered in relatively young people,seems to be due to rupture of small, peripheral, usually apical subpleural blebs, andusually subsides spontaneously as the air is resorbed.Recurrent attacks are common and can be quite disabling.
13When the defect acts as a flap valve Pneumothorax may have as much clinical significance as a fluid collection in the lungsalso causes compression, collapse, and atelectasis of the lungmay be responsible for marked respiratory distressOccasionally the lung collapse is markedWhen the defect acts as a flap valvepermits the entrance of air during inspiration but fails to permit its escape during expiration,it effectively acts as a pump that creates the progressively increasing pressures of tension pneumothorax,which may be sufficient to compress the vital mediastinal structures and the contralateral lung
14Pleural tumors Pleura may be involved by primary or secondary tumors Primary pleural tumorsSolitary (Localized) Fibrous TumorsMalignant mesotheliomasSecondary pleural tumorsprimary neoplasms of the lung and breastAny organ of body
15Secondary metastatic involvement far more common than are primary tumorsmost frequent metastatic malignancies arise fromprimary neoplasms of the lung and breastmalignancy from any organ of the body may spread to the pleural spaces.Ovarian carcinomas, for example, tend to cause widespread implants in both the abdominal and thoracic cavitiesIn most metastatic involvements, a serous or serosanguineous effusion follows that often contains neoplastic cellsFor this reason, careful cytologic examination of the sediment is of considerable diagnostic value
16Solitary (Localized) Fibrous Tumors Previously called "benign mesothelioma" or "benign fibrous mesothelioma" in the pleura and "fibroma" in the lung,localized fibrous tumors are now recognized as soft tissue tumors with a propensity to occur in the pleura and, less commonly, in the lung, as well as other sites.often attached to the pleural surface by a pediclemay be small (1 to 2 cm in diameter) or may reach an enormous size,but it tends to remain confined to the surface of the lungdo not usually produce a pleural effusion.
17Solitary (Localized) Fibrous Tumors Grossly, they consist of dense fibrous tissue with occasional cysts filled with viscid fluid;microscopically, the tumors show whorls of reticulin and collagen fibers among which are interspersed spindle cells resembling fibroblasts.Rarely, these tumors may be malignant, with pleomorphism, mitotic activity, necrosis, and large size (>10 cm).The tumor cells are CD34+ and keratin-negative by immunostainingThis feature can be diagnostically useful in distinguishing these lesions from malignant mesotheliomas (which show the opposite phenotypeThe solitary fibrous tumor has no relationship to asbestos exposure.
18Malignant mesotheliomas in the thorax arise from either the visceral or the parietal pleuraAlthough uncommon, they have assumed great importance in the past few yearsbecause of their increased incidence among people with heavy exposure to asbestosIn coastal areas with shipping industries in the United States and Great Britain and in Canadian and South African mining areas, up to 90% of reported mesotheliomas are asbestos-related.The lifetime risk of developing mesothelioma in heavily exposed individuals is as high as 7% to 10%.There is a long latent period of 25 to 45 years for the development of asbestos-related mesothelioma,and there seems to be no increased risk of mesothelioma in asbestos workers who smoke.This is in contrast to the risk of asbestos-related lung carcinoma,already high,markedly magnified by smoking.Thus, for asbestos workers (particularly those who are also smokers), the risk of dying of lung carcinoma far exceeds that of developing mesothelioma.
19Clinical Course presenting complaints are; chest pain, dyspnea, and, recurrent pleural effusions.Concurrent pulmonary asbestosis (fibrosis) is present in only 20% of patients with pleural mesotheliomaThe lung is invaded directly, and there is often metastatic spread to the hilar lymph nodes and, eventually, to the liver and other distant organs.Fifty per cent of patients die within 12 months of diagnosisfew survive longer than 2 years.Aggressive therapy appears to improve this poor prognosis in some patientsextrapleural pneumonectomy, chemotherapy, radiation therapy