Visibility of Histoplasma within histiocytes on hematoxylin and eosin distinguishes disseminated histoplasmosis from other forms of pulmonary histoplasmosis.

The visibility of Histoplasma within histiocytes on hematoxylin and eosin is a well-known feature of disseminated histoplasmosis. However, it is unclear whether this finding can be used to differentiate disseminated histoplasmosis involving the lung from other forms of pulmonary histoplasmosis. The aim of this study was to determine whether the visibility of Histoplasma within histiocytes on hematoxylin and eosin in lung biopsies suggests disseminated disease. Lung biopsies in which Histoplasma was identified were re-examined to determine whether organisms were visible within histiocytes on hematoxylin and eosin. Clinical findings were reviewed retrospectively to determine the type of histoplasmosis. Histoplasma was visible within histiocytes on hematoxylin and eosin in lung biopsies from 4 patients (2 men, 2 women, 50-74 years) who presented with pulmonary manifestations without definite evidence of disseminated disease at the time of biopsy. Subsequently, all 4 manifested clinical and/or microbiologic features of disseminated disease (positive extrapulmonary cultures and fatal outcome in 2, positive extrapulmonary cultures in 1, and multiorgan failure and fatal outcome in 1). In contrast, organisms were identified on silver stains but could not be visualized on hematoxylin and eosin in 42 patients, none of whom showed clinical or microbiologic evidence of disseminated disease (pulmonary histoplasmoma, 38; acute pulmonary histoplasmosis, 4). In lung biopsies, the visibility of Histoplasma within histiocytes on hematoxylin and eosin suggests disseminated disease. Recognition of the significance of this finding is helpful in diagnosing disseminated disease in patients who present primarily with pulmonary manifestations without definite clinical evidence of dissemination at the time of biopsy.