Leukemia cutis designates involvement of the skin by cells of leukemia of any kind. It is uncommon compared with skin lesions caused by adverse effects of drugs, thrombocytopenia, and infections that are rather commonly encountered in leukemic patients. The clinical diagnosis of leukemia cutis is often difficult because the presentations are variable. The histopathologic diagnosis of leukemia cutis is especially problematic when no hint to the diagnosis is given by the referring clinician. Sometimes, leukemia cutis appears prior to obvious manifestation of leukemia in the peripheral blood, so-called "aleukemic leukemia cutis." Whereas dermatopathologists at university hospitals with a strong hematology department may see leukemic infiltrates with a certain frequency, dermatopathologists in private practices rarely make the diagnosis of specific infiltrations in the skin. Therefore, many colleagues are lacking in experience with criteria for diagnosis of this condition.

Available literature on the subject comprises isolated case reports of diagnostically difficult cases of leukemia cutis and few studies on larger groups of patients.[1–28] These studies emphasize that diagnosis of leukemia cutis often requires integration of clinical, histopathologic, and immunohistochemical findings, the foundation of it being proper interpretation of biopsy specimens stained with hematoxylin and eosin. Immunohistochemical investigations may, at times, be helpful in identifying the nature of cells in infiltrates, but no single distinctive marker has been established that enables detection of leukemic cells in the skin with surety. The value of molecular cytogenetic techniques in routine diagnosis of leukemia cutis remains to be demonstrated. Criteria for histopathologic diagnosis, however, are often given short shrift in textbooks of dermatology, dermatopathology, and pathology.[29–31] Articles and paragraphs in textbooks on the subject include only very few images of clinical lesions and photomicrographs of histopathologic features. Therefore, we present here an account of 34 patients with leukemia cutis of our own experience and we share with readers a large amount of pictorial material assembled by us in order to increase awareness of colleagues about criteria for diagnosis and differential diagnosis of leukemia cutis.