b-cell Prolymphocytic Leukemia

B-cell prolymphocytic leukemia (B-PLL) is a rare lymphoproliferative disorder with clinical, morphologic, and immunophenotypic features that overlap with other mature B-cell leukemias and lymphomas. Patients with B-PLL typically have marked splenomegaly and leukocytosis, have no significant lymphadenopathy, and have a clinically aggressive course and poor prognosis. In peripheral blood (PB) and bone marrow (BM) aspirate smears, numerous large prolymphocytes with a round to oval nucleus and a single large nucleolus are observed. The French-American-British group recommends requiring that >55% prolymphocytes be present in the PB (or BM) to establish the diagnosis of B-PLL. In BM biopsy sections, B-PLL extensively replaces the medullary space in a pattern that is diffuse, interstitial, or both. Immunophenotypic studies have shown that B-PLL patients express monotypic immunoglobulin light chain (of bright intensity) and pan-B-cell antigens, and variably express the CD5 antigen. Cytogenetic studies have reported several chromosomal abnormalities, which are usually complex. The differential diagnosis of B-PLL is reviewed.