Plasmacytoid dendritic cell clusters are associated with poor prognosis in chronic myelomonocytic leukemia

Chronic myelomonocytic leukemia (CMML) is associated with high rates of transformation to acute myeloid leukemia (AML) and poor overall survival. Plasmacytoid dendritic cell (pDC) proliferations in bone marrow biopsies have been proposed to be prognostically significant in CMML. In this multi-institutional study, we quantified pDC clusters in bone marrow biopsies of patients with CMML by interferon regulatory factor 8 (IRF8) immunohistochemical staining performed in separate laboratories and demonstrated the association of pDC clusters with overall survival. Two hundred five newly diagnosed CMML cases were scored for the presence of prominent pDC clusters, which were detected in 37 cases (18%). The median overall survival (OS) was 15.1 months for patients with pDC clusters versus 30.1 months for those without pDC clusters (p = 0.021 log-rank test, Kaplan-Meier analysis). We propose using IRF8 immunohistochemistry in CMML bone marrow evaluation.