Displaying exciting clinical outcome of BKT inhibitor, ibrutinib, in patients with mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) [33–35], ibrutinib and other BTK inhibitors are now undergoing clinical testing for multiple myeloma, yet important questions on the role of BTK in myeloma biology and treatment are still outstanding. This evidence concerns the gene BTK and mantle cell lymphoma.