Morphology - Table 4

	[Last Modified: ]

Table 4
Differential Morphology of Protozoa Found in Stool Specimens of Humans: Amebae-Cysts

			NUCLEUS			CYTOPLASM
Species	Size (Diameter or length)	Shape	Number	Peripheral Chromatin	Karyosomal Chromatin	Chromatoid Bodies	Glycogen
Entamoeba histolytica	10-20 mm Usual range, 12-15 mm.	Usually spherical.	4 in mature cyst. Immature cysts with 1 or 2 occasionally seen.	Peripheral chromatin present. Fine, uniform granules, evenly distributed.	Small, discrete, usually centrally located.	Present. Elongated bars with bluntly rounded ends.	Usually diffuse. Concentrated mass often present in young cysts. Stains reddish brown with iodine.
Entamoeba hartmanni	5-10 mm Usual range, 6-8 mm.	Usually spherical.	4 in mature cyst. Immature cysts with 1 or 2 often seen.	Similar to E. histolytica.	Similar to E. histolytica.	Present. Elongated bars with bluntly rounded ends.	Similar to E. histolytica.
Entamoeba coli	10-35 mm Usual range, 15-25 mm.	Usually spherical. Occasionally oval, triangular, or other shapes.	8 in mature cyst. Occasionally super-nucleated cysts with 16 or more are seen. Immature cysts with 2 or more occasionally seen.	Peripheral chromatin present. Coarse granules irregular in size and distribution, but often appear more uniform than in trophozoites.	Large, discrete, usually eccentric but occasionally centrally located.	Present, but less frequently seen than in E. histolytica. Usually splinter-like with pointed ends.	Usually diffuse, but, occasionally well defined mass in immature cysts. Stain reddish brown with iodine.
Entamoeba polecki	9-18 mm Usual range, 11-15 mm.	Spherical or oval.	1. Rarely 2. Occasionally visible in unstained preparations.	Usually fine granules evenly distributed.	Usually small and eccentric.	Present. Many small bodies with angular or pointed ends, or few large ones. May be oval, rod-like, or irregular.	Usually small, diffuse masses stain reddish brown with iodine. A dark area called an "inclusion mass" (possibly concentrated cytoplasm) is often also present. Mass does not stain with iodine.
Endolimax nana	5-10 mm. Usual range, 6-8 mm.	Spherical, ovoidal, or ellipsoidal.	4 in immature cysts. Immature cysts with less than 4 rarely seen.	None	Large (blot-like), usually central.	Occasionally granules or small oval masses seen, but bodies as seen in Entamoeba spp. are not present.	Usually diffuse. Concentrated mass seen occasionally in young cysts. Stains reddish brown with iodine.
Iodamoeba buetschlii	5-20 mm. Usual range, 10-12 mm	Ovoidal, ellipsoidal, triangular, or other shapes.	1 in mature cyst.	None	Large, usually eccentric. Refractile, achromatic granules on one side of karyosome. Indistinct in iodine preparations.	Occasionally granules present, but chromatoid bodies as seen in Entamoeba spp. are not present.	Compact, well-defined mass. Stains dark brown with iodine.

Table 4 of 11