Cytology

In human tissue, leishmanial parasites appear as amastigotes that multiply within histiocytes. Amastigotes are ovoid or round and 1.5-3 µm in diameter (up to 5 µm in smears). They have a thin cell membrane, a relatively large nucleus, and a rod-shaped kinetoplast that is not always visible in tissue sections because of the orientation of the parasite.

Polyparasitic syndromes, such as early-stage and diffuse CL, are easily confirmed with Giemsa-stained smears. Oligoparasitic syndromes, such as late-stage (healing) CL, are difficult or impossible to confirm with standard Giemsa-stained smears.