[Waldenström macroglobulinemia: Japanese perception].

Waldenström macroglobulinemia (WM) is a rare low-grade B-cell lymphoma. This report focuses on WM in Japan. Regarding epidemiology, per the 2016 registry data by the Japanese Society of Hematology, WM and lymphoplasmacytic lymphoma (LPL) cases were 229 and 125, respectively (1.97% of 17,957 mature lymphoid malignancies), with the annual incidence of WM/LPL in Japan 2.8 per million. In addition, 6q deletion (6q del) is the leading aberration and one of the poor prognostic factors in WM. Our findings suggested that the serum IgM level was higher in WM with 6q del compared with those without, and the B-cell receptor signaling pathway and IL-21 receptor expression were activated in WM with 6q del. Hence, these findings might be attributed to the aggressiveness of the WM with 6q del. Regarding treatment, recent studies investigating the epidemiological treatment pattern for WM have reported rituximab (R) monotherapy and alkylating regimen (±R) as the leading initial treatment. Nevertheless, ideal treatment algorithm in Japan warrants further investigation.