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Wednesday, 30 September 2020

BINUCLEATED LYNPHOCYTES CHARACTERISTIC OF POLYCLONAL B-CELL LYNPHOCYTOSIS

Written by Silvia Montolio Breva | Rafael Sánchez Parrilla | Isabel Fort Gallifa

Figure 1. Binucleated lymphocytes in peripherical blood smear (May-Grünwald-Giemsa) in a polyclonal b-cell lymphocytosis patient.

An image of an extension of peripheral blood smear, stained with May-Grünwald-Giemsa, is presented (figure 1). It is observed binucleated lymphocytes. These entities are constant and they are almost a exclusive feature of persistent polyclonal B lymphocytosis (LBPP). Morphologically, the lymphocytes are medium-large in size with a moderately condensed, bilobed nucleus, with a broad and slightly basophilic cytoplasm, as seen in the image. In addition, it is also common to observe the presence of lymphocytes with a central incisure nucleus, more or less deep that represents the different evolutionary stages prior to the binucleated lymphocyte (figure 2).
img2Figure 2. Lymphocytes with nuclear incisuration belonging to prior stages to binucleated lymphocyte (peripheral blood smear, May-Grünwald-Giemsa).

It is a routine analysis in a 38-year-old smoker woman, in the blood count was observed a moderate lymphocytosis (6.11 x 109 / L), so it was decided to  study the peripheral blood smear under a microscope finding the presence of binucleated lymphocytes (<10%), which guided the diagnosis towards a LBPP.

LBPP is a rare entity first described in 1982 by Gordon et al. which mainly affects, but not exclusively, young or middle-aged women, usually smokers. It is characterized by a maintained mild-moderate lymphocytosis that usually ranges between 5 and 15_x_109/L although there are cases with normal count of lymphocytes. They are usually clinically asymptomatic patients.

The diagnostic criteria for LBPP, besides the characteristic lymphocyte morphology, are a polyclonal increase of IgM levels with normal or low values of the rest of immunoglobulins. Lymphocytes always express markers of mature B lymphocytes such as CD19, CD20, CD22, CD79b, CD27 or FMC7 and the absence of markers such as CD5, CD10, CD23, CD43 or CD103, as well as a normal kappa / lambda ratio.

It is important and necessary, given the find of lymphocyte binuclearity, to make diagnosis with other malignant monoclonal  lymphoproliferative  syndromes such as B prolymphocytic leukemia, tricoleukemia or splenic marginal zone lymphoma, corroborating the polyclonal origin of the entity by immunophenotype, cytogenetics and molecular biology.

In the present case, in order to confirm the diagnostic orientation, the determination of immunoglobulins and proteinogram in serum was extended, as well as the immunophenotype in blood. The results obtained showed an increase in IgM (1031_mg/dL) without alterations in the proteinogram. In addition, the immunophenotype was also compatible with a LBPP highlighting the expression of mature B lymphocyte markers as well as the absence of CD5 and the presence of polyclonal surface chains.

Finally, it is worth mentioning that it is still necessary to clarify whether the LBPP is a benign pathology or a premalignant condition. For this reason, follow-up of these patients is recommended.

REFERENCES

  1. Woessner S, Florenca L. La citología óptica en el diagnóstico hematológico. 5th ed. España: Grupo Acción Médica, S.A.; 2006.
  2. Merino A. Casos clínicos de hematología. 2014-2015. Ed Cont Lab Clin; 22: 36-48.
  3. Troussard X, Cornet E, Lesesve JF, Kourel C, Mossafa H. Polyclonal B-cell lymphocytosis with binucleated lymphocytes (PPBL). OncoTargets Ther. 2008 I; 59-66.
  4. Aydos N, Schneider L, Michel B, Beno F, Moreira GA. Polyclonal B-cell Lymphocytosis: Report of Three Cases. Cytom. Part B-Clin. Cytom. 2018 94B; 953-955.

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