Problems when diagnosing cutaneous leishmaniasis: a retrospective study analyzing clinical, histopathological and immunohistochemical features

Background: Cutaneous leishmaniasis (CL) incidence in Switzerland is rising due to factors like migration and globalization. The aim of this work was to investigate CL frequency in Switzerland and identify clinical and histopathological difficulties in diagnosing CL in a non-endemic country. Patients and methods: This retrospective study evaluated the clinical and histopathological characteristics of all CL cases from two dermatopathology laboratories between 2000 and 2022. Skin biopsies were histopathologically reviewed using HE, Giemsa, and immunohistochemical stain for CD1a and a specific Leishmania antibody (LA). PCR to detect Leishmania DNA was performed if sufficient tissue was available. Results: 42 cases (27 m, 15 f) were included. The correct clinical diagnosis of CL was only made in 15 (35.7%) cases. In seven (16.6%) cases, CL was missed in the initial histopathologic evaluation. Two main histopathological patterns were observed: granulomatous and pseudolymphomatous. Immunohistochemical staining with CD1a and Leishmania-specific antibody was positive in 91% and 80% of cases, respectively. Leishmania PCR was positive in 25 of 26 cases, mainly detecting Old World species. Conclusions: CL is rare in Switzerland and often misdiagnosed clinically and histopathologically. CD1a and specific Leishmania antibody stainings are useful. CL should be considered in non-healing ulcers, even without a history of travel to endemic areas.