Leukemia cutis as the presenting symptom of acute myeloid leukemia: report of three cases.

Leukemia cutis (LC), a rare cutaneous manifestation of leukemia, can precede, follow, occur concurrently with, or present in the absence of (aleukemic) systemic leukemia. Leukemia cutis is especially rare as the presenting symptom of leukemia and is associated with a poor prognosis. Although more commonly seen in acute leukemias of myeloid and monocytic lineage, lymphocytic/lymphoblastic leukemias can also involve the skin. Three cases of LC presented with diverse skin lesions ranging from an erythematous rash to violaceous macules and papules to subcutaneous nodules. One case clinically mimicked fixed drug eruption. All the patients had acute myeloid leukemia (AML). Lesions showed two overarching histologic patterns: atypical perivascular infiltrate or nodular dermal histiocytoid infiltrate. Our cases expressed myeloperoxidase (MPO), a helpful marker to distinguish myeloid from non-myeloid cells, and CD68, a monocytic marker frequently expressed in cutaneous AML. CD14, a marker of monocyte maturity, was negative. In the absence of systemic leukemia, common diagnostic tools for hematologic malignancies such as bone marrow biopsy and flow cytometry are non-contributory, making morphologic and immunohistochemical analysis of the skin lesions key to diagnosis.