Congenital leukemia cutis.

We describe a premature neonate who was born with pancytopenia and a single subcutaneous nodule on her right lower extremity. A biopsy specimen from the nodule demonstrated a dense infiltrate of pleomorphic mononuclear cells that extended throughout the dermis and into the subcutaneous tissue. Immunohistochemical stains and bone marrow examination confirmed a diagnosis of acute myelogenous leukemia. Cytogenetic studies on peripheral blood by G-banding analysis revealed an abnormal karyotype of 46, XX, insinv(10)(p11.2q22.2);11. A split in the mixed lineage leukemia gene was identified by fluorescence in situ hybridization. Induction chemotherapy was started but was complicated by multiorgan failure. The patient died on the eleventh day of life. As leukemia cutis more typically presents as multiple infiltrative papules, nodules, or plaques, we stress the importance of including leukemia in the differential diagnosis of a solitary nodule in a neonate.