Twenty-one cases of blastic plasmacytoid dendritic cell neoplasm: focus on biallelic locus 9p21.3 deletion.

Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) is a rare and aggressive malignancy derived form precursors of plasmacytoid dendritic cells. We analyzed 21 cases with array-based comparative genomic hybridization (array-CGH). Complete or partial chromosomal losses largely outnumbered the gains, with common deleted regions (CDR) involving 9p21.3 (CDKN2A/CDKN2B), 13q13.1-q14.3 (RB1), 12p13.2- p13.1 (CDKN1B), 13q11-q12 (LATS2), and 7p12.2 (IKZF1) regions. CDKN2A/CDKN2B deletion was confirmed by Fluorescence In-Situ Hybridization (FISH). This scenario argues for disruption of cell cycle at G1/S transition, representing a genetic landmark of BPDCN, and possibly contributing to its pathogenesis. Statistical analysis of overall survival in our series highlighted an association of poor outcome with biallelic loss of locus 9p21.3. We suggest that, in the absence of reliable parameters for predicting prognosis in BPDCN other than age, tumor stage and/or clinical presentation, simple methods such as FISH for CDKN2A/CDKN2B could help to identify the most aggressive cases.