Dissecting Splenic B Cell Lymphoma/Leukaemia with Prominent Nucleoli (SBLPN) by Flow Cytometry: Experience from a Stand-Alone Reference Laboratory

Abstract

Background: Splenic B-cell lymphoma/leukaemia with prominent nucleoli (SBLPN) is a rare chronic B-cell lymphoproliferative malignancy, comprising approximately 0.4% of all chronic lymphoid malignancies, with a reported annual incidence of 0.03 per million. Although prominent nucleoli with polar cytoplasmic projections are considered distinctive features of SBLPN, their assessment is often subjective and requires an experienced observer, which may lead to an imprecise diagnosis. Molecular studies are limited and inconclusive. Flow cytometry is often indispensable for the accurate characterisation of such atypical lymphoid cells. Method: The study was an observational study of 10 cases diagnosed as SBLPN. The samples were processed using the stain-lyse-wash procedure and analysed using the BD FACSCANTO II analyser with BD FACS Diva software v9.0. A gating strategy using bright CD19 versus low side scatter was employed to analyse the lymphocyte population. A Matutes-based scoring system incorporating the HCL markers CD11c, CD103, CD123, and CD25 was used. Result: SBLPN is a CD5-, CD10-, and CD25-negative B-cell lymphoproliferative disorder with positivity for CD11c and CD103. Of the 10 cases, eight had a score of 2 out of 4, while two had a score of 3 out of 4. None of the cases had a score of 0, 1, or 4. Conclusion: SBLPN is a CD5-, CD10-, and CD25-negative B-cell lymphoproliferative disorder with positivity for CD11c and CD103. The Matutes immunophenotypic score using the four markers remains relevant and usually yields a lower score in SBLPN.