Leukemia Cutis from CD56 Positive, Myeloperoxidase Negative Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a clonal expansion of myeloid blasts in peripheral blood, bone marrow, or other tissues. Cutaneous manifestations of leukemia are either specific or nonspecific. Specific lesions result from direct infiltration of the skin by leukemic cells. We present a case of myeloid leukemia cutis manifested by erythematous asymptomatic nodules and plaques distributed on the chest, abdomen and back. The clinical and histopathologic features of the cutaneous infiltrate were suggestive of hematolymphoid malignancy, more towards lymphoma. However, the immunohistochemical features were against the diagnosis of lymphoma and were highly suspicious of myeloid leukemia, which were concomitantly confirmed by bone marrow biopsy and blood smear. In any poorly differentiated malignant skin infiltrate of confirmed hematopoietic lineage, myeloid differentiation should be considered and excluded by an appropriate panel. CD56+ AML is a rare type of AML that has special features like the great liability of extramedullary involvement including skin, monocytic characteristic of leukemia cells, and absence of myeloperoxidase expression.