Central nervous system involvement by Waldenström macroglobulinaemia (Bing‐Neel syndrome): a multi‐institutional retrospective study

Summary Bing‐Neel syndrome ( BNS ) is a rare complication seen in patients with Waldenström macroglobulinaemia ( WM ), in which lymphoplasmacytic lymphoma cells colonize the central nervous system. In this retrospective multi‐centre study, we present the clinicopathological features, imaging findings, therapy, response and outcomes of 34 patients with BNS . The median time from WM diagnosis to BNS diagnosis was 3 years, 15% of patients were diagnosed with BNS at the time of WM diagnosis, and 22% of patients developed BNS when responding to active treatment for WM . Patients with BNS presented with variable clinical features including limb motor deficits, change in mental status and cranial nerve palsies. The diagnosis was made using a combination of cerebrospinal fluid cytology, flow cytometry and detection of the MYD 88 L265 mutation, and magnetic resonance imaging. The estimated 3‐year overall survival rate was 59%. Of the survivors, 40% have evidence of pathological and/or radiological persistence of disease. Age older than 65 years, platelet count lower than 100 × 10 9 /l, and treatment for WM prior to BNS diagnosis were associated with worse outcome. Exposure to rituximab for treatment of BNS was associated with a better outcome. Multi‐institutional collaboration is warranted to improve treatment and outcomes in patients with BNS .