Cutaneous accumulation of plasmacytoid dendritic cells associated with acute myeloid leukemia: a rare condition distinct from blastic plasmacytoid dendritic cell neoplasm.

A cutaneous infiltrate composed of plasmacytoid dendritic cells may occasionally occur in a patient suffering from a myeloid neoplasm. To date, the clinical and pathological features associated with this event remains poorly characterized. Herein, we report a patient with acute myeloid leukemia who developed pruritic papules or erythematous plaques scattered on the skin. Microscopic examination showed a dermal infiltrate rich in plasmacytoid dendritic cells expressing CD4, CD43, CD68, granzyme B, CD123, CD303 [blood dendritic cell antigen 2 (BDCA-2)], CD2-associated protein (CD2AP) and T-cell leukemia/lymphoma oncogene 1 (TCL1). Our observation illustrates further that cutaneous lesions associated with some myeloid neoplasms, especially those featuring a monocytic component, may be composed of plasmacytoid dendritic cells. Because of differences in clinical, pathological and genetic features, this rare condition should be distinguished from blastic plasmacytoid dendritic cell neoplasm.