Morphologic features of binucleated lymphocytes to assess the diagnosis of persistent B-cell polyclonal lymphocytosis or other mature B-cell neoplasms

Cytogenetics in the management of clonal chromosomal abnormalities of undetermined significance and persistent polyclonal B-cell lymphocytosis: Guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

Acquired clonal chromosomal abnormalities (CAs) are usually considered to be disease-related. However, when a CA of this type is the only abnormality present (and especially in small clones), the clinical significance is unclear. Here, we review the literature on recurrent CAs whose significance is regularly subject to debate. Our objective was to help with their interpretation and develop guidelines for sex chromosome loss, trisomy 15, trisomy 8, deletion 20q and other isolated non-myelodysplastic neoplasm (MDS)-defining CAs. We suggest that non-MDS-defining CAs correspond to clonal hematopoiesis of indeterminate potential (CHIP) in the absence of cytopenia and clonal cytopenia of undetermined significance (CCUS) in the presence of cytopenia. Lastly, we review the literature on persistent polyclonal binucleated B-cell lymphocytosis; although usually benign, this condition may correspond to a premalignant state.

Abnormal characteristic "round bottom flask" shape volume-based scattergram as a trigger to suspect persistent polyclonal B-cell lymphocytosis

BACKGROUND AND AIMS

The diagnosis of persistent polyclonal B-cell lymphocytosis (PPBL) is often challenging because of the lack of features and the overlap with the peripheral expression of splenic marginal zone lymphomas (SMZL). To obtain new clues for PPBL detection and diagnosis, all data provided by the DxH 800 analyzer (including scatter and cell population data (CPD)) was exploited and combined using a machine learning (ML) approach.

MATERIALS AND METHODS

A total 211 samples from 101 normal controls and 110 patients (PPBL and SMZL) were assessed. Age, gender, full blood count, CPD, scatter, flags and CellaVision differentials were also considered. A ML model was built for true classification purposes.

RESULTS

PPBL and SMZL shared increased absolute lymphoid counts, atypical lymphoid flag presence and CPD values (8 out of 14). A typical "round-bottom-flask" shape scattergram was described for the first time for PPBL which was also present in 51.4% of SMZL cases. The developed ML model render a global classification accuracy of 93.4%, allowing the detection of all pathological cases, with mean misclassification rates of 12% among PPBL and SMZL.

CONCLUSION

Our ML model represents a new unbiased tool than can be widely applied in the laboratory as an aid for detection of PPBL.

The frequency of occurrence of atypical lymphocytes in peripheral blood smears of natalizumab-treated patients with multiple sclerosis

INTRODUCTION

Aside from the extensive published data on immunophenotypic lymphocyte subsets in natalizumab-treated patients with multiple sclerosis (MS), an impact of natalizumab on lymphocyte morphology has rarely been studied. As patients treated with immunomodulating or immunosuppressive drugs are at risk for infectious disorders such as viral infections, knowledge of drug-derived changes in lymphocyte morphology may be beneficial in the diagnostic work-up in such clinical situations. This study aimed to determine the frequency of occurrence of atypical lymphocytes and defined subtypes of variant lymphocytes in natalizumab-treated patients with MS.

METHODS

We compared eight defined morphological lymphocyte subtypes in peripheral blood smears between 14 natalizumab-treated, 13 interferon-treated and 10 untreated subjects with relapse-remitting MS.

RESULTS

Atypical lymphocytes were significantly enhanced in natalizumab-treated patients compared to the interferon and control group (P<.0001). Binucleated lymphocytes were restricted to the natalizumab group (P=.0058, P=.018), and plasmacytoid lymphocytes were more frequently found in the natalizumab group (P<.0001).

CONCLUSION

Our data indicate that natalizumab enhances the fraction of atypical lymphocytes, and thereby especially the binucleated and plasmacytoid lymphocytes. Knowledge of these natalizumab-associated changes in lymphocyte morphology may be relevant in clinical routine, to avoid unnecessary diagnostic procedures or even a discontinuation of natalizumab treatment.