Yeast Fungi

Histoplasmosis (Histoplasma capsulatum)

An H&E stain (left) shows macrophages filled with organisms giving the cytoplasm a slightly vacuolated appearance. A GMS stain (right) shows the clustered organisms in the cytoplasm.

Multiple, oval, budding, intracellular yeast, 3 µm in diameter, occupy a macrophage. The halo is a shrinkage artifact and not a capsule.

Blastomycosis (Blastomyces dermatitidis)

Purulent granulomas or granulomatosis is characteristic of the reaction to this yeast. Note the numerous PMNs mixed with epithelioid cells. Giant cells were present elsewhere. The arrow indicates the only organism. Shrinkage artifact produces the halo around this budding organism.

A GMS stain shows the broad-based, budding yeast, 8-15 µm in diameter.