#00065160

A 57yo female presented with spontaneous bruising, some skin lesions and mild itching, as well as cytopenias of unknown cause. Peripherial blood and bone marrow demonstrated numerous medium-sized blastoid cells. Initially this was sent for ?T-ALL investigations.

Immunophenotyping of both the peripheral blood and the bone marrow demonstrated an abnormal population with mid CD45 expression and low side scatter that had positive expression for: CD56, CD7, CD33, HLADR, CD4, CD26 and NG2.  And negative expression for CD34, CD19, CD10, CD5, CD2, CD3, CD25, CD30, CD16, CD57, TCRa/b, TCRg/d, CD1a, CD38, cytMPO, cytTDT, cytCD3, cytCD79a. This was reported as acute leukaemia with no lineage-defining markers detected, suspicion for T-ALL given morphology and some T-cell markers.

Further immunophenotyping work later demonstrated CD123 positivity. This phenotype (CD7+ CD4+ CD56+ CD123+ HLADR+) is most suggestive of BPDCN, retrospectively supported by the morphology and clinical presentation.

Blastic plasmacytoid dendritic cell neoplasm with involvement in the peripheral blood is a very clinically aggressive tumour derived from plasmacytoid dendritic cells with a high frequency of cutaneous and bone marrow involvement and leukemic dissemination. BPDCN has previously been referred to as blastic NK-cell lymphoma and agranular CD4+ NK-leukaemia