IBTK and hematopoietic and lymphoid system neoplasm: In several types of blood cancers, infiltration ofmalignant whiteblood cells occurs in the central nervous system (CNSi) and is onlydetected in 3–5% of patients at initial diagnosis, and 30–40%of patients at relapse.33 In relapsed andrefractory MCL CNSi, monotherapy with BTKi has been proven to be effective,with an objective response rate of 68%.