The grains in clinical material are tiny and red in color. In section, the grain is rounded, oval or semi-lunar. It stains a purple color and compact hyphae give it the appearance of “Iron filings”. The periphery of the grain has a narrow deeply eosinophilic band. The grain is usually surrounded by a zone of neutrophils, which causes fragmentation of the grain. The other layers are similar to those seen in S. somaliensis but the giant cells are less conspicuous.
The ultra-structure of the grain is quite distinctive. The hyphae are septate, compact without cement substance and under low magnification the hyphae have a starry sky appearance because of the vacuoles in the hyphae. These are probably fixation artifacts. Neutrophils usually adhere to the grain and degranulate. Grain material is phagocytozed by the neutrophils and destroyed.