The presence of a large glycogen mass in an immature amebic cyst can help identify which organism?

• A. Dientamoeba fragilis
• B. Endolimax nana
• C. Entamoeba coli
• D. Entamoeba histolytica

Answer: (C)

Amoebic cysts are identified by their internal features, especially the number of nuclei and any glycogen or other inclusions present. In immature cysts of Entamoeba coli, a relatively large glycogen mass is a characteristic finding before maturation, making it a distinctive clue. This glycogen reserve sets E. coli apart from other intestinal amoebae: Dientamoeba fragilis is typically diagnosed by trophozoites and doesn’t rely on a cyst glycogen pattern; Endolimax nana cysts are smaller and have a different nuclear appearance (large karyosome) rather than a prominent glycogen mass; Entamoeba histolytica cysts usually show four nuclei and chromatoidal bodies rather than a large glycogen inclusion. So, spotting a large glycogen mass in an immature cyst most strongly points to Entamoeba coli.