[Successful diagnosis of lymphoplasmacytic lymphoma with IgG paraprotein using MYD88 L265P mutation analysis].

A 76-year-old woman presented to our hospital with leukocytosis and abnormal lymphocytes. M protein of the immunoglobulin G (IgG) type was detected using immunoelectrophoresis. A bone marrow biopsy revealed infiltration of small mature lymphocytes, lymphoplasmacytoid cells with Dutcher bodies, grape cells, and Russell bodies. The MYD88 L265P mutation was detected in the abnormal peripheral lymphocytes, and a diagnosis of lymphoplasmacytoid lymphoma was established. MYD88 L265P mutation analysis is useful for making a diagnosis of non-IgM lymphoplasmacytoid lymphoma because it enables the differentiation from other low-grade B-cell malignancies.