"Semi-invasive" pulmonary aspergillosis: a new look at the spectrum of aspergillus infections of the lung.

A chronic cavitary form of pulmonary aspergillosis may occur with mild immunosuppression or underlying lung disease. In this "semi-invasive" type, the fungus is intermediate between a simple saprophyte and an invasive pathogen. Aspergillus may produce extensive lung destruction despite the lack of vascular invasion. The absence of a previous cavity distinguishes such cases from secondary noninvasive mycetomas. Radiographic features include a chronic infiltrate, progressive cavitation, and subsequent mycetoma formation. Biopsy may be helpful; however, marked squamous metaplasia can produce false-positive Class V cytological findings even though malignancy is excluded. This variety of aspergillosis supports the concept that the traditional allergic, saprophytic, and invasive forms may represent a spectrum of disease dependent on host immune status and lung architecture.