Bone marrow infiltration by cells resembling plasmablasts in a patient with blastic plasmacytoid dendritic cell neoplasm

Abstract

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a clinically aggressive hematologic malignancy derived from clonal proliferation of plasmacytoid dendritic cells. The disease has two patterns of presentation: cutaneous and leukemic. Herein we describe the case of a 9-year-old boy who presented with an unusual morphologic variant of leukemic BPDCN, showing bone marrow infiltration by medium to large cells with eccentric nuclei, regular round to oval shape, finely dispersed chromatin, one or more distinct nucleoli, and abundant basophilic cytoplasm, forming a pattern that resembled plasmablasts. Multiparameter flow cytometric immunophenotyping confirmed the diagnosis of BPDCN by identifying the expression of CD4++, CD56++, HLA-DR+++, and CD123+++ in abnormal cells, without significant expression of myeloid or lymphoid lineage-specific markers. Awareness of this plasmablastic variant of BPCDN can be helpful for directing the flow cytometry panel and the subsequent investigation of patients presenting with bone marrow infiltration by cells with plasmablastic features.