Myeloid nuclear differentiation antigen: an aid in differentiating lymphoplasmacytic lymphoma and splenic marginal zone lymphoma in bone marrow biopsies at presentation

90 LPL and 91 SMZL cases. MYD88 p.Leu265Pro mutation status was assessed and confirmed as pos-itive in 24 of 90 LPL cases, which served as the test set. MNDA staining was negative in 23 of 24 LPL cases in the test set (96%). In the 157 remaining cases (66 LPL, 91 SMZL), which served as the vali-dation set, the MYD88 p.Leu265Pro mutation was unavailable and MNDA was more frequently ex-pressed in SMZL (p < 0.00001). In addition, immunohistochemical features more consistent with SMZL (i.e., presence of CD23 thorn follicular dendritic cell meshworks, polytypic plasma cells, DBA44 reactivity) were more often present in MNDA-positive cases (statistically significant for 2 such param-eters). On the widest case series so far published focusing on LPL and SMZL immunohistochemical diagnosis at onset of BMB, we demonstrated that MNDA expression significantly support the diagnosis of SMZL. This observation may be of particular help in cases where the MYD88 p.Leu265Pro muta-tional status and/or SMZL-related genetic aberrations are unavailable. (c) 2022 Published by Elsevier Inc.