To better characterize pulmonary
candidiasis, lung tissue samples from 58 hospital subjects were examined by immunohistochemical 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 noncandidal mycotic, 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.