CD23 expression in lymphoplasmacytic lymphoma: Clinical–pathological and biological correlations

Aims: The diagnosis of lymphoplasmacytic lymphoma (LPL) in the bone marrow (BM) is challenged by aberrant phenotypes and by overlapping histological features with marginal zone lymphoma (MZL). To address these issues, we (i) assessed LPL immunophenotype on a large series of BM samples, (ii) drew possible correlations between LPL phenotype and clinical/molecular data and (iii) investigated the role of new phenotypical markers in the differential diagnosis between LPL and MZL. Materials and methods: The study retrospectively considered 81 clinically annotated LPL diagnosed at Padua University Hospital (Padua, Italy) during a 5-year period. BM findings were correlated with clinical laboratory findings and with MYD88 and CXCR4 mutational status. The obtained results were compared with a series of 77 MZL in the BM, including 46 splenic MZL (SMZL), 14 nodal MZL (NMZL) and 17 extra-nodal MZL (EMZL). Results: The LPL cohort included 52 males and 29 females (median age at diagnosis = 71 years). Aberrant CD10 and CD5 positivity was documented in 3 of 81 (3.7%) and 13 of 81 (16.1%) cases, respectively. CD23 positivity occurred in 56 of 81 (69.1%) cases, being usually partial/focal. CD23 expression did not correlate with any specific clinical-pathological parameter. Comparison with SMZL, NMZL and EMZL highlighted less frequent splenomegaly, higher serum paraprotein, higher CD23 expression and fewer follicular dendritic cell networks in LPL. A combined clinical-pathological score supported the differential diagnosis between LPL and MZL of any type. The highest diagnostic yield was obtained for the differential diagnosis between LPL and SMZL. Conclusions: Partial positivity for CD23 is a common feature of LPL in the BM. Together with other clinical and histological parameters, CD23 expression supports the differential diagnosis between LPL and MZL.