A 70-year-old man presented with a purplish plaque on his cheek. A skin biopsy revealed a diffuse dermal infiltration of medium-sized atypical cells with fine chromatin and scant cytoplasm. The atypical cells were positive for CD4, CD56, CD123, and TCL-1 (Figure 1). Histopathologic findings were consistent with a diagnosis of blastic plasmacytoid dendritic cell neoplasm. One year later, the patient developed pancytopenia, and a bone marrow biopsy revealed an interstitial infiltration by blastic plasmacytoid dendritic cells (Figure 2).
Siavash Toosi, M.D.
Resident, Anatomic and Clinical Pathology
Rebecca King, M.D.
Senior Associate Consultant, Division of Hematopathology
Assistant Professor of Laboratory Medicine and Pathology,
Mayo Clinic College of Medicine