Nonneoplastic Conditions

Bacterial pneumonia: lobar pneumonia can be of rapid onset in otherwise healthy patients and entire lobes are involved by neutrophilic infiltrates. Bronchopneumonia affects older debilitated patients and is characterized by more circumscribed infiltrates.

Lung abscess: an area of infection with parenchymal necrosis. Primary lung abscess occurs more often on the right side as the right main bronchus leads more directly off the trachea and aspiration can occur more easily. Secondary abscesses occur when there are predisposing factors such as carcinoma, foreign body or bronchiectasis.

Viral infection: may occur in the lungs due to respiratory viruses such as influenza or in the immunocompromised patient (cytomegalovirus, respiratory syncytial virus, Varicella zoster or Herpes simplex). Histological examination shows alveolar cell injury with a mononuclear cell interstitial infiltrate.

Tuberculosis: the characteristic histological lesion is the caseating granuloma. Primary TB presents with a solitary parenchymal nodule and hilar lymph node involvement. Secondary TB may present as miliary TB, tuberculous pneumonia or cavitary TB.

Mycotic infections: tangled masses of fungal hyphae and debris may be found in lung cavities and are known as fungal balls. These are usually non-invasive unless the patient is immunocompromised. Aspergillus fumigatus is the most common cause, the fungal balls being called aspergillomas. Surgery may be needed for diagnosis and treatment of disease resistant to medical treatment.

Pneumocystis carinii: a fungal organism, which occurs in immunocompromised patients. There is an acellular intra-alveolar exudate. Silver stains or antibody techniques demonstrate the organism.

Chronic bronchitis and emphysema: often occur together. Emphysema is characterized by an increase in the size of airspaces distal to the terminal bronchioles. It is classified into three types depending on the part of the lung involved by the process - centrilobular, panlobular (panacinar) and paraseptal. Chronic bronchitis results from hypersecretion from bronchial mucous glands.

Bronchiectasis: permanent abnormal dilatation of the bronchi with infection of the bronchial wall and obliteration of distal airways. Cystic fibrosis is the most common predisposing factor.

Endogenous lipoid pneumonia: may occur distal to a lung tumour and is secondary to breakdown of lung parenchyma. The alveoli contain lipid-laden macrophages.

Pneumoconiosis: defined as permanent alteration of lung structure due to the inhalation of mineral dusts and the tissue reactions which follow this. Included in this group are silicosis, asbestosis, coal worker's pneumoniosis, hard metal disease and berylliosis. Asbestosis is a form of interstitial fibrotic lung disease secondary to asbestos exposure. Fibrosis is characteristically found in the lower lobes especially in the subpleural areas. Asbestos bodies are present in the lung parenchyma. Asbestosis may be graded depending on the amount of lung substance involved and the severity of the fibrosis. Other asbestos-related conditions include benign pleural plaques, diffuse pleural thickening and malignant mesothelioma. The incidence of carcinoma of the lung is increased in those with a history of asbestos exposure.

Interstitial pneumonia/cryptogenic fibrosing alveolitis/pulmonary fibrosis: chronic inflammatory disease, which shows thickening of the alveolar walls, initially by lymphocytes and plasma cells, later by fibroblastic proliferation. Eventually "honeycomb lung" is produced with scarring and multiple air-filled spaces. The need to assess both spatial and temporal distribution of the pathology means that open or thoracoscopic lung biopsies from different zones are usually required. Of clinical value is the sub-classification of interstitial pneumonia as prognosis and response to treatment varies between subgroups. These include usual interstitial pneumonia (UIP), desquamative interstitial pneumonia (DIP), respiratory bronchiolitis-associated interstitial lung disease (RBILD) and non-specific interstitial pneumonia (NSIP). Prognosis and response to treatment are worse for UIP than other subgroups (five-year survival 55%).

Immune-mediated lung diseases: extrinsic allergic alveolitis is a chronic granulomatous disease of the lungs due to inhalation of organic dusts, e.g., farmer's lung, bird-fancier's lung, mushroom worker's lung. Upper lobes are more severely affected than basal portions with fibrotic changes occurring in advanced disease.

Wegener's granulomatosis: in the lungs is characterized by vasculitis and granulomas.

Sarcoidosis: occurs most often in the lungs although lymph nodes, skin, eyes, liver and spleen may also be affected. Characteristically, sharply circumscribed non-caseating epithelioid granulomas are present and 25% of cases show marked interstitial fibrosis.

Rare conditions include Langerhans cell histiocytosis, lymphomatoid granulomatosis and pulmonary lymphangioleiomyomatosis.

Pulmonary vascular disease: emboli that lodge in peripheral arteries cause pulmonary infarcts in patients whose pulmonary circulation is already compromised.

Pulmonary hypertension: primary or secondary. Changes in the arteries may be graded according to the Heath-Edward's classification.

Lung transplantation: the most common indication for lung transplantation is emphysema, e.g., secondary to alpha-1-antitrypsin deficiency. Other indications include chronic obstructive pulmonary disease, septic disease such as cystic fibrosis, fibrotic lung disease and primary pulmonary hypertension. Surveillance involves transbronchial biopsy to look for rejection, which is graded according to the 1995 working classification.

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