BTK and B-cell chronic lymphocytic leukemia: 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.