B-Cell Prolymphocytic Leukemia (B-PLL)

Definition

B-cell prolymphocytic leukemia is a more aggressive, but still treatable, form of chronic lymphocytic leukemia (CLL). The malignant B cells are larger than average. The name is commonly abbreviated B-PLL. It has a relatively poor prognosis.

Sample Cases

Click here for instructions on how to download the free FCS Express Reader to view and manipulate the sample cases.

Epidemiology

B-PLL is an extremely rare disease, comprising approximately 1% of lymphocytic leukemias. Most patients are over 60 years of age, with the median age of 70 and a male predominance (male to female ratio 1.6 to 1)

Possible causes

Morphology

Peripheral blood and bone marrow: The majority (>55% and usually >90%) of the circulating cells are prolymphocytes - medium sized cells (twice the size of benign lymphocytes) with a round nucleus, moderately condensed nuclear chromatin, a prominent central nuceoli, and a relatively small amount of faintly basophillic cytoplasm. Some nuclear indentation may be present. The bone marrow shows diffuse intertrabecular infiltration by similar cells.

Tissue other than bone marrow: In the spleen, extensive white and red pulp involvement, with prolymphocytes present in both red and white pulp nodules. The nodules in the white pulp may show a bizonal appearance with packed cells in the center and larger cells in the periphery. Lymph nodes show diffuse and vaguely nodular infiltrates of similar cells.

Immunophenotyping

The cells of B-PLL strongly express surface light chains and IgM +/- IgD as well as B-cell antigens CD19, CD20, CD22, CD79a and CD79b, and FMC7. CD5 is only present in about 1/3 of the cases of B-PLL. CD5 is only positive in cases arising from CLL.  The expression of CD20 (and surface Ig) as compared to CLL. CD23 is generally absent.

Other relevant tests

Sub-classification

PLL can transform from CLL. de novo cases of PLL must be distinguished from CLL transformation, as the latter has a worse prognosis.

Flow Diagnosis

The cells in B-PLL strongly express surface Ig (kappa or lambda) and surface IgM as well as B cell markers CD19, CD20, CD22, CD79a, CD79b, FMC7. CD5 can be expressed and CD23 is generally absent.

The differential diagnosis includes splenic MZL, MCL, B-CLL and T-PLL.

References

Lens D, Matutes E, Catovsky D, Coignet LJ (2000). "Frequent deletions at 11q23 and 13q14 in B cell prolymphocytic leukemia (B-PLL)". Leukemia 14 (3): 427-30

Del Giudice I, Davis Z, Matutes E, et al (2006). "IgVH genes mutation and usage, ZAP-70 and CD38 expression provide new insights on B-cell prolymphocytic leukemia (B-PLL)". Leukemia 20 (7): 1231-7.

Contributors to this page