Persistent Polyclonal B-Cell Lymphocytosis with Binucleated Lymphocytes

To the Editor,

A 46-year-old female was admitted to our clinic suffering from long-standing leukocytosis. She was evaluated at another hospital regarding this lymphocytic leukocytosis (absolute lymphocyte count: 10770/µL) with no final diagnosis despite further work-up including bone marrow sampling.

She was a heavy smoker for at least 50 pack-years. We wanted to reassess the underlying disease and ordered a new complete blood count and a peripheral blood smear (Figure 1). We noticed the abundance of binucleated lymphocytes in the peripheral smear.

Figure 1

Abundant binucleated lymphocytes with some ghost cells. May-Grunwald-Giemsa staining, 100x.

Persistent polyclonal B-cell lymphocytosis (PPBL) does not have a distinctive phenotype. Flow cytometry is performed for the exclusion of a clonal B lymphoid disorder (Figure 2). The patient was diagnosed with PPBL according to the further work-up and was informed about the benign nature of the disease.

Figure 2

Immunophenotypic features of non-clonal B lymphocytes.

PPBL is an infrequent benign disease first described in 1982, characterized by the abundance of binucleated lymphocytes [1]. The immunophenotype of PPBL shows an expansion of B-cells that usually express CD19, CD20, CD22, CD27, and CD79b and are commonly negative for CD5, CD10, CD23, and CD38, with a normal kappa/lambda light chain ratio [2,3]. PPBL often shows an indolent, stable course over many years or slight progress with continued smoking, so the diagnosis of PPBL is crucial in order to avoid unnecessary procedures and therapeutic measures.