Case #192 – November, 2006

A request for confirmation of an identification was submitted to DPDx Telediagnosis Assistance. Figures A and B were captured from a hematoxylin and eosin (H & E) stained histological section of a liver abscess found during an autopsy. The patient had a travel history to Sri Lanka. What is your diagnosis? Based on what criteria?

Figure A

Figure B

This was a case of invasive extraintestinal amebiasis caused Entamoeba histolytica. Diagnostic features were:

the size of the nuclei in the trophozoites, which is smaller than those seen in macrophages. The ratio for macrophages is generally 1:4 to 1:6, whereas the E. histolytica/dispar ratio is 1:10 to 1:12.
nuclei with even peripheral chromatin. In Figure B a distinct central karyosome was present (black arrow). In pathological preparations all morphologic features may not be visualized due angle of the cuts.
location of these organisms in liver tissue, which is consistent with invasive extraintestinal amebiasis and rules-out the morphologically-similar, E. dispar.

Figure B

In addition to finding organisms in tissue, antigen detection or molecular testing should be considered for a confirmatory diagnosis.