A Phase 4, Observational Study Evaluating the Efficacy and Safety of the Bruton Tyrosine Kinase (BTK) Inhibitor Zanubrutinib in Patients With Waldenström Macroglobulinemia

Inclusion Criteria: * Clinical and definitive histologic diagnosis of WM * Measurable disease, as defined by a serum immunoglobulin M (IgM) level \> 0.5 g/dL at the time of zanubrutinib initiation * Started treatment with zanubrutinib, has been treated with zanubrutinib, or is planned to be prescribed zanubrutinib for the treatment of WM * Bone marrow specimens with central MYD88 test results of: 1. Cohort 1: MYD88 L265P mutation; enrollment of TN participants will be stopped in each racial and ethnic participant group when the required numbers of participants in the group are met 2. Cohort 2: non-L265P MYD88 mutation(s) and MYD88WT Exclusion Criteria: * Evidence of disease transformation before the first dose of zanubrutinib * Evidence of other non-Hodgkin Lymphoma (NHL) subtypes * Prior or concurrent active malignancy ≤ 2 years before the first dose of zanubrutinib, except for malignancies that, in the investigator's opinion, will not obscure the interpretation of safety or efficacy results * Concurrent participation in another therapeutic clinical study while receiving zanubrutinib, although the participant may be eligible depending on the status of the interventional study after discussion with the Medical Monitor or designee on an individual basis