phils, lymphocytes, and macrophages [6]. Lucent centers seen in large nodules correspond to a dilated bronchiole surrounded by thickened peribronchiolar interstitium. Thickand thinwalled cystic lesions seen on CT consist of a central cavity surrounded by a thick and thin wall composed of Langerhans cell sheets and eosinophils. In thin-walled cysts, inßammatory cell inÞltrations along the alveolar walls as well as pericystic emphysema are seen. Bizarre cysts seen on CT have irregular and wavy wall on pathology, and the walls of cystic lesions are composed of numerous Langerhans and other inßammatory cells or Þbrotic changes. Several cysts coalesce with surrounding cysts via the destruction of their walls.

Patient Prognosis

The natural history of the disease is widely variable and unpredictable [19]. Approximately 50 % of patients experience a favorable outcome, with after the cessation of smoking or with glucocorticoid therapy. Approximately 10Ð20 % of patients have early severe manifestations, consisting of recurrent pneumothorax or progressive respiratory failure. Finally, 30Ð40 % of patients show persistent symptoms of variable severity that remain stable over time.

Septic Pulmonary Embolism

Pathology and Pathogenesis

Septic pulmonary embolism causes lung abscess and septic infarction. Localized suppurative necrosis of lung tissue and cavitation containing necrotic ßuid or debris are observed.

Symptoms and Signs

Septic pulmonary embolism is an uncommon disorder presenting with fever; respiratory symptoms such as cough, sputum, hemoptysis, chest pain, and dyspnea; and lung inÞltrates in the presence of an extrapulmonary source of infection [22]. Since infected thrombus can cause lung abscess, septic infarction, empyema, bronchopleural Þstula, shock, and death; respiratory symptoms are variable and often nonspeciÞc. Historically, septic pulmonary embolism has been associated with intravenous drug use, pelvic thrombophlebitis, and suppurative processes in the head and neck. However, increasing use of indwelling catheters and devices as well as increasing numbers of immunocompromised patients has changed the epidemiology and clinical manifestations of septic pulmonary embolism.

CT Findings

Septic pulmonary embolism is characterized by the presence of multiple nodules that usually measure 1Ð3 cm in

diameter and that frequently cavitate [23] (Fig. 12.3). The nodules often have ill-deÞned margins and have a feeding vessel sign [14]. The subpleural wedge-shaped areas of consolidation often with central areas of necrosis or cavitation are also seen. According to a study, cavitation within the nodules is more common in pulmonary septic embolism caused by gram-positive microorganisms, whereas ill-deÞned margins are more common in pulmonary septic embolism caused by gram-negative microorganisms [24].

CT-Pathology Comparisons

Nodules seen on CT correspond to areas of infarction and hemorrhage caused by ischemia and neutrophilic exudates and necrosis of lung parenchyma caused by toxins from organisms. The subpleural wedge-shaped areas of consolidation correspond to areas of hemorrhage or infarction caused by occlusion of pulmonary arteries by septic emboli.

Patient Prognosis

Early diagnosis is the most important to improve the prognosis. With appropriate antimicrobial therapy and control of the infectious source, resolution of the illness and avoidance of potential complications can be expected.

Cavitary Pulmonary Tuberculosis

Pathology and Pathogenesis

Pulmonary tuberculosis (TB) is usually seen as a necrotizing consolidative process predominantly in lung apices. Pulmonary TB may be seen as a Ghon lesion (1Ð2 cm, round, white-gray pulmonary nodule with central necrosis), a Ghon complex (Ghon lesion plus hilar lymphadenopathy), or a Ranke complex (Þbrosis and calciÞcation of the Ghon complex via cell-mediated immunity). Histologically, both necrotizing (caseating) and nonnecrotizing granulomas can be seen in lung parenchyma or lymph nodes. Organisms (4-μm beaded rods) can be demonstrated using acid-fast stains (ZiehlÐNeelsen), although a negative acid-fast stain does not rule out tuberculosis. Langerhans-type multinucleated giant cells are frequently seen [25] (Fig. 12.4).

Symptoms and Signs

Cough is the most common symptom of pulmonary TB. Cavitary pulmonary TB is often accompanied by hemoptysis. Constitutional symptoms, including fever, malaise, fatigue, weight loss, night seating, and anorexia, are often present [26].