To better characterize pulmonary candidlasis, lung tissue samples from 58 hospital subjects were examined by immunohistocnemical analysis with antiserums to candidal mannan and cytoplasmic antigens. In nine cases of invasive pulmonary candidiasis, fungal antigens were abundant in lung specimens and were distributed in two immunohistologic patterns. Antigen dissemination beyond the lung was confirmed by detection of antigenemia by mannan radioimmunoassay in serum samples in cases of pulmonary candidiasis of each immunohistologic pattern. In contrast, minimal, focal quantities of fungal antigens were detected in lung tissue specimens from nine subjects with thrush or aspiration but without pulmonary candidiasis; no antigen was detected in 40 additional cases of noncandldal mycotlc, bacterial, viral, and parasitic pneumonias. Immunohistochemical criteria that denote invasive pulmonary candidiasis include the abundance of diffuse candidal antigens in bronchiolar and alveolar fluid and cytoplasmic staining of phagocytes. When compared with routine histologic stains, the diagnostic yield in cases of invasive pulmonary candidiasis was significantly increased by detection of candidal antigenic material. This study of 58 well-documented cases shows that immunohistochemical detection of candidal antigens facilitates the diagnosis of candidal pneumonia and distinguishes clinically significant pulmonary candidiasis from noninvasive aspiration, opportunistic colonization, or specimen contamination.
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