The successful application of molecularly informed therapy has been demonstrated in Waldenström’s macroglobulinemia (WM) lymphoplasmacytic lymphoma (LPL) where about 90% of patients have a dominant mutation in MYD88L265P, an adapter protein used by toll-like receptors that mediate signaling through Bruton tyrosine kinase (BTK) to promote proliferation and survival [41]. The gene discussed is BTK; the disease is Waldenstrom macroglobulinemia.