1- (3- (4-Amino-3- (4-phenoxyphenyl) -1H-pyrazolo [3,4-d] pyrimidin-1-yl) piperidin-1-yl) prop-2-en-1-one or a pharmaceutically acceptable salt thereof for use in the treatment of Waldenström macroglobulinemia.1-(3-(4-Amino-3-(4-fenoxifenil)-1H-pirazolo[3,4-d]pirimidin-1-il)piperidin-1-il)prop-2-en-1-ona o una sal farmacéuticamente aceptable de la misma para usar en el tratamiento de la macroglobulinemia de Waldenström.