Background
Cutaneous T-cell lymphoma is a challenging diagnosis given its rarity and heterogeneity in presentation. The ISCL/EORTC algorithm for the diagnosis of early mycosis fungoides (the most common form of CTCL) highlights the histopathologic presence of a superficial lymphoid infiltrate plus epidermotropism without spongiosis or lymphoid atypia, and the immunopathologic features of CD2,3,5 expression in < 50% of T-cells, CD7 expression in <10% of T-cells and epidermal discordance from expression of CD2,3,5 or CD7 on dermal T-cells as key diagnostic criteria.
Case Discussion
A 30 year-old patient from a jungle-like area of Lima, Peru presented for a progressive thigh lesion. A skin biopsy demonstrated a T-cell lymphoproliferative disorder (T-LPD) with CD8+ and partial CD4/CD8 double negative phenotype. PET/CT showed hypermetabolic nodular lesions at the cutaneous/subcutaneous plane on the thigh/knee. Repeat biopsy of the lesion revealed: infiltrate of lymphocytes and macrophages, some possibly activated lymphocytes/lymphoblasts, surface ulcerated with bacterial colonies, some macrophages displaying vacuolated cytoplasm with possible intracellular organisms resembling Leishmania species. IHC revealed a predominance of CD3+ cells with slight predominance of CD4 over CD8 and mostly preserved CD7 expression. Anti-CD1a labeled Langerhans cells but appeared negative within the infiltrate. Smears showed organisms consistent with Leishmania. Peripheral blood flow cytometry showed no aberrant T cell population. Given the preserved expression of T cell markers and CD7 expression, and Giemsa stain showing parasitic organisms, it was concluded that this biopsy showed a reactive lymphohistiocytic infiltrate consistent with Leishmania infection.
Conclusion
Careful multidisciplinary pathologic review is ideal when evaluating cases of CTCL. The chronic inflammation of cutaneous leishmaniasis must be differentiated from a T-LPD using stains to identify the parasite (Giemsa), and possibly CD1a, to support the diagnosis of Leishmania, along with correlation with clinical history given organisms can be scarce in chronic lesions of leishmaniasis recidivans and L.V. braziliensis infections.