S11C23P18-Protozoan Infections

S11C23P18-1: In this lesion of cutaneous leishmaniasis, scattered aggregates of pale, epithelioid histiocytes interrupt what would otherwise be a diffuse intiltrate of lymphoid cells. The infiltrates press upon the epidermis; the rete ridges are effaced.

S11C23P18-2: The activated histiocytes are loosely clustered. The clusters are spotty in distribution. The lesion has granulomatous qualities.

S11C23P18-3: In this cluster of activated histiocytes, some of the cells are vacuolated. There are scattered lymphocytes. Organisms in the cytoplasm of the histiocytes are small; they appear as basophilic “dots” that are outlined by clear haloes (leishmaniasis).

S11C23P18-4: Typical organisms are present at the tips of green arrows (leishmaniasis). Some of the histiocytes contain fine, pigment granules in their cytoplasm.

S11C23P18-5: This loosely organized granuloma of the brain is associated with a cluster of organisms compatible with toxoplasmosis.

S11C23P18-6: The organisms are seen at higher magnification. They appear to be encysted.

S11C23P18-7: Green arrows identify small clusters of organisms (toxoplasmosis).

S11C23P18-8: Green arrows identify clusters of encysted organisms (leishmaniasis).

 

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