- Blastocystis hominis appear as spherical to oval cyst-like structures. They vary widely in size (5 to 30 µm; usual range 8 to 10 µm), and typically consist of a central body, or “vacuole,” surrounded by a thin rim of cytoplasm containing up to six nuclei.
- The vacuoles stain variably from red to blue in trichrome stain, which is preferred to wet mounts as the organisms can be overlooked as debris .