Primary Plasma Cell Leukemia: Recent Advances in Molecular Understanding and Treatment Approaches.

Primary plasma cell leukemia (pPCL) is a rare and aggressive plasma cell dyscrasia. According to revised diagnostic criteria, pPCL is defined by the presence of ≥5% circulating plasma cells (CPCs) in the peripheral blood of patients with newly diagnosed multiple myeloma (NDMM). pPCL is characterized by a distinct cytogenetic profile, including frequent t(11;14), translocations, 1q gain, and del(17p). While t(11;14) is generally associated with a favorable prognosis, the coexistence of multiple high-risk cytogenetic abnormalities is linked to poorer outcomes. Tandem autologous hematopoietic stem cell transplantation and novel anti-myeloma agents have improved survival in some patients; however, overall prognosis remains poor, particularly in those ineligible for transplantation. Venetoclax and emerging immunotherapies, such as CAR-T cells and bispecific antibodies, show promise and merit clinical trials focused on pPCL-enriched cohorts. Additionally, recent findings associating even minimal CPCs with adverse outcomes in NDMM support broader inclusion criteria in future trials. A deeper understanding of pPCL's molecular pathology is critical for the development of effective targeted therapies. This article reviews recent advances in the molecular understanding of and treatment strategies for pPCL.