The trophozoites of Entamoeba histolytica/Entamoeba dispar measure 10 to 60 micrometers in greatest dimension (usual 15 to 20 micrometers) and have granular cytoplasm and a small round nucleus. The chromatin pattern is described as 'dot and ring' with a small central (or eccentric) karyosome and peripheral rim of condensed chromatin. The trophozoites of E. histolytica, the definitive pathogen, are morphologically identical to the trophozoites of E. dispar, as well as those of Entamoeba moskovskii and Entamoeba bangladeshi, and therefore cannot be definitively identified by morphology alone. The only exception to this is when ingested red blood cells are seen within the trophozoite cytoplasm, since this allows for a presumptive identification of Entamoeba histolytica.