Acute myelomonocytic leukemia presenting as a benign-appearing cutaneous eruption

Aleukemic leukemia cutis is a rare condition in which patients have skin lesions containing leukemic cells before evidence of leukemia can be detected in the peripheral blood. There are only 23 cases of this phenomenon documented in the English literature. We describe a 62-year-old woman who developed a diffuse, clinically benign-appearing cutaneous eruption, which histologically showed an atypical infiltrate of cells, 4 months before leukemic cells were found in her peripheral blood and the diagnosis of acute myelomonocytic leukemia was made by bone marrow aspiration. This case illustrates the difficulty in diagnosing leukemia cutis from examination of routine histologic sections and the importance of specialized marker studies in determining the cause of an atypical cellular infiltrate of the skin. It also illustrates how leukemia cutis can masquerade as a clinically benign-appearing cutaneous eruption in a seemingly healthy patient with normal blood parameters.