Blastic Plasmacytoid Dendritic Cell Neoplasm Developed in Chronic Myeloid Leukemia in Molecular Remission During a Four-Year Treatment-Free Interval After Six Years of Dasatinib Treatment.

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare hematological malignancy affecting multiple sites, most commonly the skin. About 10-20% of BPDCN cases are accompanied by hematological neoplasms. A 71-year-old male was diagnosed with chronic myeloid leukemia in the chronic phase (CML-CP) 11 years prior (at 60 years of age), and dasatinib treatment was initiated. A major molecular response (MMR) was achieved 18 months after diagnosis, and the molecular response (MR)4.0 lasted beyond 36 months. Due to pancytopenia, dasatinib was discontinued at 74 months, but the CML-CP remained undetectable. One hundred and twenty-two months after the diagnosis, the patient presented with cutaneous lesions on the forehead and abdomen. Immunological and histological analyses of the skin biopsy showed infiltration of atypical cells from the deep epidermis to the entire dermis, expressing clusters of differentiation (CD) 4, CD56, and CD123 without any other markers. The same cells were observed in bone marrow samples. BPDCN was diagnosed, followed by chemotherapy and possibly autologous or allogeneic hematopoietic stem cell transplantation (HSCT). To the best of our knowledge, this is the first case report of the development of BPDCN in a patient with CML in molecular remission. Further studies are required to clarify the pathogenesis of BPDCN in patients with hematological malignancies in remission.