Blastic Plasmacytoid Dendritic Cell Neoplasm: A Case Report of a Rare and Aggressive Hematologic Malignancy.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a strikingly unusual, clinically challenging, and rapidly spreading tumor that originates from plasmacytoid dendritic cell (PDC) precursors. It has a high incidence of skin and bone marrow involvement as well as leukemic dissemination. It shows a considerable biologic diversity with overlapping morphologic and immunophenotypic features of various cutaneous hematolymphoid neoplasms. Studies with large series of patients are not available due to low prevalence and short survival of the disease. We report here a rare case of BPDCN in a 30-year-old male patient who primarily came with skin manifestations almost all over the body surface. Skin biopsy revealed monomorphic medium-sized undifferentiated blast-like cells filling the entire dermis sparing the epidermis. The cells were immunopositive for CD45, CD56, CD4, and CD123 with a high Ki-67 labeling index while they were negative for known B-cell and T-cell markers. Radiological evaluation revealed lymphadenopathy at various sites. Peripheral blood smears and bone marrow aspiration smears demonstrated similar blast-like cells. Misdiagnosis or late diagnosis of this clinically heterogeneous BPDCN may lead to systemic spread and poor outcomes. Hence, prompt diagnosis and treatment are essential, with a multidisciplinary approach.