BTK and Waldenstrom macroglobulinemia: Bruton tyrosine kinase (BTK), a key component of B-cell receptor (BCR), plays a prominent role in the survival of many B-cell malignancies, and has thereby become an attractive target for the treatment of B-cell malignancies, such as chronic lymphocytic leukemia (CLL), mantle-cell lymphoma (MCL), Waldenström’s Macroglobulinemia (WM) and diffuse large B cell lymphoma (DLBCL) [1,2,3].