B-cell Prolymphocytic Leukemia : Introduction
Introduction: B-cell prolymphocytic leukemia (B-PLL) is an extremely rare lymphoid malignancy of mature B cells that accounts for about 1% of all lymphocytic leukemias. Prolymphocytes invade the peripheral blood, bone marrow, and spleen. By definition, prolymphocytes must exceed 55% of lymphoid cells in the peripheral blood (actual numbers > 90% in most cases). B-PLL was initially considered a variant of chronic lymphocytic leukemia (CLL) but has since been recognized as a distinct entity in the revised WHO classification of lymphoid neoplasms in 2016. Close mimics such as CLL with increased prolymphocytes and leukemic phase of mantle cell lymphoma must be excluded. B-PLL occurs in the elderly and is characterized by aggressive clinical course, poor response to first-line chemotherapy drugs, and dismal prognosis (median survival 3 years). Image courtesy of: Teresa Scordino, MD; used with permission.