Page 492 - Textbook of Pathology, 6th Edition

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Figure 17.14 Lung abscess. A, The pleura is thickened. Cut surface of the lung shows multiple cavities 1-4 cm in diameter, having irregular and
ragged inner walls (arrow). The lumina contain necrotic debris. The surrounding lung parenchyma is consolidated. B, The photomicrograph shows
abscess formed by necrosed alveoli and dense acute and chronic inflammatory cells.

from preceding pneumonia and septic or pyaemic allergic bronchopulmonary aspergillosis, aspergilloma and
abscesses are often multiple and scattered throughout the necrotising bronchitis. Immunocompromised persons develop
lung. more serious manifestations of aspergillus infection,
especially in leukaemic patients on cytotoxic drug therapy
Grossly, abscesses may be of variable size from a few and HIV/AIDS. Extensive haematogenous spread of
millimeters to large cavities, 5 to 6 cm in diameter. The aspergillus infection may result in widespread changes in
SECTION III
cavity often contains exudate. An acute lung abscess is lung tissue due to arterial occlusion, thrombosis and
initially surrounded by acute pneumonia and has poorly- infarction.
defined ragged wall. With passage of time, the abscess
becomes chronic and develops fibrous wall (Fig. 17.14,A). Grossly, pulmonary aspergillosis may occur within
Histologically, the characteristic feature is the destruction preexisting pulmonary cavities or in bronchiectasis as fungal
ball.
of lung parenchyma with suppurative exudate in the lung
cavity. The cavity is initially surrounded by acute Microscopically, the fungus may appear as a tangled mass
inflammation in the wall but later there is replacement by within the cavity. The organisms are identified by their
chronic inflammatory cell infiltrate composed of characteristic morphology— thin septate hyphae with
lymphocytes, plasma cells and macrophages. In more dichotomous branching at acute angles which stain positive
chronic cases, there is considerable fibroblastic for fungal stains such as PAS and silver impregnation
Systemic Pathology
proliferation forming a fibrocollagenic wall (Fig. 17.14,B). technique (Fig. 17.15). The wall of the cavity shows chronic
inflammatory cells.
CLINICAL FEATURES. The clinical manifestations are 2. Mucormycosis. Mucormycosis or phycomycosis is
fever, malaise, loss of weight, cough, purulent expectoration caused by Mucor and Rhizopus. The infection in the lung
and haemoptysis in half the cases. Clubbing of the fingers occurs in a similar way as in aspergillosis. The pulmonary
and toes appears in about 20% of patients. Secondary lesions are especially common in patients of diabetic
amyloidosis may occur in chronic long-standing cases. ketoacidosis. Mucor is distinguished by its broad, non-parallel,
nonseptate hyphae which branch at an obtuse angle.
Mucormycosis is more often angioinvasive, and
FUNGAL INFECTIONS OF LUNG
disseminates; hence it is more destructive than aspergillosis.
Fungal infections of the lung are more common than 3. Candidiasis. Candidiasis or moniliasis caused by Candida
tuberculosis in the US. These infections in healthy individuals albicans is a normal commensal in oral cavity, gut and vagina
are rarely serious but in immunosuppressed individuals may but attains pathologic form in immunocompromised host.
prove fatal. General aspects of mycotic infections are covered Angioinvasive growth of the organism may occur in the
in Chapter 7. Here, some common examples of fungal airways.
infections of the lung are briefly given:
4. Histoplasmosis. It is caused by oval organism, Histoplasma
1. Aspergillosis. Aspergillosis is the most common fungal capsulatum, by inhalation of infected dust or bird droppings.
infection of the lung caused by Aspergillus fumigatus that The condition may remain asymptomatic or may produce
grows best in cool, wet climate. The infection may result in lesions similar to the Ghon’s complex.