Incidence and characteristics of CD4(+)/HLA DRhi dendritic cell malignancies

Recent reports suggest that CD4(+)/CD56(+)/lineage(-) hematopoietic neoplasias are aggressive types of malignancies involving lymphoplasmacytoid/DC2 dendritic cells (DC). Here, we report on the incidence of DC malignancies and their clinical, biological, phenotypic and cytogenetic characteristics.

From a large series of 392 patients with acute myeloblastic leukemia (AML) and 739 with non-Hodgkin's lymphoma (NHL), five cases (three presenting as acute leukemia and two as NHL) showed clinical, morphologic and phenotypic features compatible with a DC malignancy.

The overall incidence of DC malignancies among all AML and NHL cases was 0.76% and 0.27%, respectively. At presentation, these patients displayed cutaneous nodules, splenomegaly and lymph node involvement with variable levels of peripheral blood (PB) and/or bone marrow (BM) infiltration in association with anemia and thrombocytopenia. Cytologic studies showed immature appearing blast cells with negative cytochemistry reactions for both myeloperoxidase and esterases. A highly suggestive DC phenotype based on co-expression of CD123(hi)/HLADR(+)/lin(-)/CD56(+)/CD45(dim) associated with a germline configuration of both the IgH and TCRgamma genes was found in all except one patient who was CD56(-). Expression of other markers compatible with a DC origin was found in all cases.

We show that DC-derived malignancies can present as either cutaneous lymphoma or acute leukemia, although their incidence is extremely low (<< >1%). While most of these DC neoplasias probably correspond to the malignant counterpart of DC2/lymphoplasmacytoid DC, neoplasias of myeloid DC might also exist, chemotherapy followed by consolidation with ASCT is apparently the most effective strategy for achieving a durable remission in these individuals.