Despite recurrent and activating mutations, including MYD88, CXCR4, ARID1A, KMT2D, and CD79B were identified, the genetic basis for Waldenström's Macroglobulinemia (WM) and the risk of progression of IgM MGUS to WM remain to be fully elucidated. Here, CD79B is linked to Waldenstrom macroglobulinemia.