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Case 216 - Discussion

Hematopathology Case

 

B-Cell Prolymphocytic Leukemia

 

CLINICAL FEATURES

  • De novo chronic B-cell leukemia, > 55% circulating peripheral blood prolymphocytes

  • Exclude transformed CLL or preexisting CLL with increased prolymphocytes

  • Relatively rare tumor, accounting for <1% or less of lymphoid leukemias

  • Males slightly more commonly than females

  • Median age, 65 - 70 years

  • Presentations:

    • Marked leukocytosis, frequently >100 × 109/L, with absolute lymphocytosis

    • Splenomegaly, often anemia and thrombocytopenia

    • No or minimal lymphadenopathy

PERIPHERAL BLOOD FINDINGS

  • Prolymphocytes

    • Cell size: medium, minimal cell-to-cell variability

    • Nucleus: round without significant nuclear membrane irregularity, moderately condensed chromatin (not finely dispersed), a single prominent nucleolus

    • Cytoplasm: minimally to moderately abundant, well-defined borders

BONE MARROW FINDINGS

  • Typically show extensive diffuse or interstitial involvement of the marrow space

  • May have a focal nodular, nonparatrabecular pattern

  • Tumor cells relatively uniform, small to medium size, prominent small central nucleolus and a rim of amphophilic cytoplasm

SPLEEN FINDINGS

  • Involvement of both red and white pulp regions, with expansion of red pulp sinusoids and white pulp

IMMUNOPHENOTYPE

  • Positive: CD19, CD20, CD22, CD79a, FMC7

  • Monotypic surface light-chain immunoglobulin

  • Aberrant CD5 antigen expression in <50% of cases

  • CD23 negative

CYTOGENETICS AND GENETICS

  • 17p-, deletion of TP53 gene, 50%
  • Lack of t(11;14)(q13;q32)

DIFFERENTIAL DIAGNOSES

  • CLL in prolymphocytic transformation: presence of a substantial population of typical CLL cells, prolymphocytes < 55%

  • Large B-cell lymphoma involving peripheral blood: rarely associated with a marked lymphocytosis, tumor cells much larger and more pleomorphic

  • T-cell prolymphocytic leukemia: often with bulky lymphadenopathy, CD4+, TCL1+

  • Mantle cell lymphoma: t(11;14), BCL1+
  • SMZL
    • Clinically, SMZL associated with relatively indolent behavior
    • Peripheral blood: variable cytologic features with PLL-like cells, plasmacytoid cells, and “villous” cells
    • Bone marrow: nodular aggregates of monocytoid cells or a subtle intrasinusoidal infiltration, in contrast to the more leukemic interstitial pattern of B-PLL
  • HCLv
    • Currently included in "splenic B-cell lymphoma/leukemia, unclassifiable"
    • Marked splenomegaly and high peripheral white blood cell counts
    • Cytologically, HCLv cells show some similarity to B-PLL cells with a single prominent nucleolus. HCLv cells retain delicate fibrillary cytoplasmic membrane borders and may have a sponge-like chromatin pattern similar to that of typical HCL or a more unusual blastoid or convoluted nuclear cytology.
    • HCLv shows a pure red pulp pattern in the spleen and an interstitial or sometimes diffuse pattern in the bone marrow
    • CD103+,  and bright CD11c and CD22