Blastic Plasmacytoid Dendritic Cell Neoplasm (BPDCN) is a very rare hematologic malignancy. Despite recent advances, at present there is no consensus on the optimal treatment of BPDCN. The optimal therapy of disease remains to be determined, and due to the rarity of cases, there is a need for international collaboration to collect data on BPDCN clinical presentations, diagnostics, treatment regimens and outcomes. Therefore, the objectives of this study are: (1) to build a large database of patients with BPDCN, (2) to investigate the characteristics and outcome of the disease with different treatment regimens, (3) to evaluate prognostic factors, and (4) to generate data-based prospective treatment recommendations.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematologic malignancy. In 2008, it was recognized by the WHO as a distinct entity and separately listed in the group of acute myeloid leukemias and related precursor neoplasms.

The final diagnosis of BPDCN relies on a compatible immunophenotype. The triple positive CD4+CD56+CD123+ phenotype associated with negativity for lineage-specific markers is a minimum requirement for defining BPDCN. The highly specific marker BDCA2/CD303, as well as other plasmacytoid dendritic cell-associated antigens (e.g. TCL1 and CD2AP), might be of great support to exclude potential mimickers of BPDCN (acute myeloid and monocytic leukemias, precursor lymphoblastic T-cell leukemia/lymphomas and T- and NK/T cell lymphomas.

At present, there is no consensus on the optimal treatment of BPDCN. The majority of patients receive multi-agent chemotherapy with AML or ALL treatment regimens, while a few patients undergo allogeneic haematopoietic stem cell transplantation (HSCT). In recent years, different novel and innovative therapies are in development to target surface molecules in BPDCN. The patients are still in need of better treatments and the optimal therapy of disease remains to be determined.

This is a multicenter, international prospective and retrospective registry with the aim of collecting data of patients with a diagnosis of BPDCN globally.

Patients will be recruited directly by the national study groups / participating centers.

Participating centers will collect and verify informed consent of all prospective patients enrolled at their center.

The following data will be collected through questionnaires:

1. Patient characteristics
2. BPDCN characteristics
3. Treatment details
4. Outcomes
5. Cause of death
6. End of data collection

Quality control and data management will be conducted by the Immune Oncology Research Institute.

Inclusion Criteria:

• Diagnosis of BPDCN
• Signed informed consent form for prospective patients

Exclusion Criteria:

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All patients with BPDCN diagnosed since 01.01.2010