Wright-Giemsa stained bone marrow aspirate at low power view shows blasts (arrow) with eccentric nucleus, moderate to abundant pale cytoplasm against a background of erythroid precursors.

Wright Giemsa stained bone marrow aspirate at higher magnification shows blasts (arrow) with eccentric nucleus having finely dispersed chromatin, moderate to abundant cytoplasm with occasional cytoplasmic vacuoles. Erythroid precursors are seen in the background. However typical circumferential microvacuolations of BPDCN blasts were not observed.

H&E stained Bone marrow biopsy is hypercellular (50% cellularity) with increased mononuclear cells (blasts) best appreciated on the top left part of the image against a background of trilineage hematopoiesis.

H&E stained Bone marrow biopsy shows medium to large sized blasts arranged in sheets with irregular nuclear contour and finely dispersed chromatin. Numerous mitotic figures are seen.

At low power, clusters of cells are positive for CD4, CD56, CD123, and TCL1.

By flow cytometry, the blasts were positive for CD4, CD7, CD56 (variable), CD123 (bright) without expression of CD19, CD3, MPO, CD34, CD64.