Ultrastructure of asteroid bodies in sporotrichosis.

Ultrathin sections were prepared from a paraffin-embedded tissue specimen which had been obtained from a sporotrichosis patient and in which large numbers of asteroid bodies had been observed. Electronmicroscopic examination of the ultrastructure of the asteroid bodies revealed a central fungal cell with peripheral rays. These cells were almost structurally identical with fungal elements found elsewhere than in asteroid bodies; and in the rays, electron-dense granular substance was arranged in layers marked by fissures and material resembling remnants of destroyed host cells. The outermost layer was formed of a granular substance of rather low electron density, surrounded by adherent cell membrane fragments. These findings suggest that an asteroid body might be composed of crystalline products of disintegrated host cells deposited around a fungal cell.