Histopathologic features of cutaneous leishmaniasis and use of CD1a staining for amastigotes in Old World and New World leishmaniasis

BackgroundPositive CD1a staining of Leishmania has been reported in Old World leishmaniasis, but the sensitivity of such staining for other Leishmania species is unknown. MethodsA retrospective review was done on skin biopsies of proven cutaneous leishmaniasis based on histology, immunohistochemistry, culture and/or polymerase chain reaction (PCR). We assessed the pattern of inflammation present and assessed for CD1a (MTB1 clone) positivity in amastigotes. Patients without a clearly documented travel history to delineate Old vs New World leishmaniasis and cases without tissue for CD1a staining were excluded. ResultsVarious patterns of granulomatous inflammation were observed including sarcoidal (31%), diffuse (25%), suppurative and granulomatous (25%), palisaded (13%) and lichenoid (6%). CD1a staining was positive in amastigotes in 9 of 16 cases (56%). Five of 7 (71%) cases of Old World disease were CD1a positive, while 4 of 9 cases (44%) of New World cases were positive. ConclusionsMultiple patterns of granulomatous inflammation occur in cutaneous leishmaniasis. Our results confirm CD1a (MTB1 clone) can be a diagnostic adjunct to highlight amastigotes in biopsies of cutaneous leishmaniasis, with variable positivity in both Old World and New World forms of the disease. As 44% of cases were CD1a negative in our cohort, there are significant limitations to this screening approach.