《Slide 41.》Amebiasis, Colon
A. Brief Descriptions：
Caused by the protozoan parasite Entamoeba histiolytica.
Infections from---E. histiolytica cysts (achitin wall & 4 nuclei).
Most frequently involves the cecum and ascending colon followed by sigmoid à rectum à appendix.
B. Gross Findings：
C. Micro Findings：
Ulcerated mucosa, edema, congestion and a prominent infiltrate of eosinophils.
Round organisms of 20-40 um diameter, some ingested RBCs (erythrophagocytosis ), are found in loose surface debris.
Enhanced recognition by periodic acid-Schiff stain.
Bowel wall or vascular invasion in severe case.
Diagnosis is best made by identified hematophagous trophozoites in fresh stools.
Robbins Pathologic Basis of Disease, 6th ed. P.358-359.
【 Fig. 41-1 (LP)】Numerous eosinophilic spherical structure within necrotic area.
【 Fig. 41-2 (HP)】The spherical structure (trophozoites) has one basophilic
nuclei about the size of RBC’s. Note some RBCs are
phagocytized by the trophozoites (erythrophagocytosis).