Entamoeba histolytica

• Mature, quadrinucleated cyst in stool specimen,
• Iron-hematoxylin stained
• Spherical or ovoidal in shape, 12-20 micrometer in diameter
• Cytoplasm  may sometimes contain dark-stained, cigar-shaped chromatoid bars
• Nuclei are relatively large.
• Each nucleus contains concentric karyosome, and peripheral chromatin evenly distributed