The stereotypical changes of an acute lesion of CL are said to be dense diffuse infiltrates of lymphocytes, plasma cells, and histiocytes with numerous gray-blue dots of Leishmania in the cytoplasm throughout the reticular dermis. [6] In our series of cases, we found that nodular infiltrates are far more common than diffuse ones. Epidermal changes such as atrophy, erosion, ulceration, spongiosis, and pustulation as well as edema of the papillary dermis indicate rather acute lesions of CL which usually have numerous intracytoplasmatic inclusions.

Tuberculoid granulomas with very few organisms in the upper half of the dermis often impinging on the epidermis are said to be diagnostic of chronic lesions of CL, but in our series of cases, tuberculoid granulomas impinging on the epidermis were more common in acute lesions of CL than in chronic ones. Chronic lesions were usually devoid of epidermal changes or showed only mild acanthosis. Granulomas in chronic lesions of CL were more often of the sarcoidal type, and intracytoplasmatic inclusions were usually few. Polymerase chain reaction performed on paraffin embedded biopsy specimens confirmed the diagnosis in these cases because histopathologic features seemed not to be diagnostic. In fact, these combinations of findings are as diagnostic of CL as are tuberculoid granulomas with numerous intracytoplasmatic inclusions.

We encountered a number of changes that are mentioned rarely in paragraphs about CL in textbooks of dermatopathology. Among them are elastophagocytosis, which was seen commonly when biopsies came from sun-damaged skin, necrosis of follicular epithelium, signs of vasculitis in the form of thrombi in the lumina of vessels or fibrin deposition in the walls of vessels, and changes of the connective tissue resembling keloidal collagen seen in dermatofibroma. An interesting finding was also the interstitial pattern assumed by histiocytes encountered in 4 cases, that pattern simulating interstitial granuloma annulare, and the presence of palisaded granulomas with fibrin in the center similar to those seen in rheumatoid nodules in 3 specimens. Involvement of the subcutaneous tissue in the form of granulomatous panniculitis was a rather common finding, it being present in half of the cases.

Plasma cells in a granulomatous dermatitis are a good clue to CL and should alert a dermatopathologist to search for intracytoplasmatic inclusions or to order PCR investigations to identify leishmania. Even though infiltrates of eosinophils usually indicate infections of the skin by parasites, eosinophils are almost never present in cutaneous leishmaniasis.

A summary of all patterns and clues to CL identified by us is given in Table 1. Our study on 30 patients with CL revealed a number of features that may help a dermatopathologist to think of a diagnosis of CL when studying a section of tissue, even when findings said to be stereotypical of CL are absent.