A clonal neoplasm of small B-lymphocytes, lymphoplasmacytoid cells, and plasma cells involving the bone marrow, lymph nodes, and the spleen. The majority of patients have a serum IgM paraprotein. The disease is lymphoplasmacytic lymphoma (Monarch Disease Ontology identifier MONDO_0000432). Also known as: Immunocytoma, lymphoplasmacytic type, lymphoma, lymphoplasmacytic, malignant, lymphoma, plasmacytic, lymphoplasmacytic lymphoma (Waldenstrom macroglobulinemia), lymphoplasmacytoid lymphoma.