Comparison of Conventional, Molecular, and Immunohistochemical Methods in Diagnosis of Typical and Atypical Cutaneous Leishmaniasis

Context.-Localized cutaneous leishmaniasis (CL) typically presents as papules, crusted nodules, plaques, or noduloulcerative lesions. Atypical CL does not show these features or mimic malignant lesion. In atypical forms, CL may be overlooked because of its similarity to other dermal diseases. Objective.-To compare conventional, molecular, and immunohistochemical methods in the diagnosis of typical and atypical CL. Design.-The kinetoplast DNA, nested, polymerase chain reaction assay and immunohistochemical methods were compared and validated against conventional methods, including cytology and pathology, using 100 specimens of typical and atypical lesions of suspected CL. Results.-Compared with other methods, polymerase chain reaction of the kinetoplast DNA showed the highest sensitivity (typical positive, 100%, 67 of 67; atypical positive, 94%, 31 of 33) and specificity (100%), followed by immunohistochemistry (typical positive, 97%, 65 of 67, with 100% specificity; atypical positives, 94%, 31 of 33, with 100% specificity), and cytology (typical positive, 79%, 53 of 67, with 100% specificity; atypical positive, 58%, 19 of 33, with 100% specificity), followed by pathology (typical positive, 70%, 47 of 67, with 100% specificity; atypical positive, 42%, 14 of 33, with 100% specificity). In addition, polymerase chain reaction enabled identification of 98% (98 of 100) of the positive samples that included strains of Leishmania major (99% [99 of 100] cases) and Leishmania tropica (1% [1 of 100] cases). Conclusions.-Because cytology is cheap and easy to perform with high sensitivity, it is the preferred, primary approach for typical CL, but cytology and pathology do not have sufficient sensitivity for diagnosis of atypical CL cases. Nested polymerase chain reaction and immunohistochemistry are sensitive tests for diagnosis of both typical and atypical CL and are recommended as complementary tests in suspected CL with negative conventional microscopy results.