Hairy cell leukemias with unmutated IGHV genes define the minor subset refractory to single-agent cladribine and with more aggressive behavior by Francesco Forconi, Elisa Sozzi, Emanuele Cencini, Francesco Zaja, Tamara Intermesoli, Caterina Stelitano, Luigi Rigacci, Filippo Gherlinzoni, Renato Cantaffa, Anna Baraldi, Andrea Gallamini, Alfonso Zaccaria, Alessandro Pulsoni, Marco Gobbi, Maristella Tassi, Donatella Raspadori, Lorenzo Leoncini, Andrea Rinaldi, Elena Sabattini, Francesco Bertoni, Stefano A. Pileri, and Francesco Lauria Blood Volume 114(21):4696-4702 November 19, 2009 ©2009 by American Society of Hematology EFS of HCL patients treated with cladribine according to prognostic parameters. Francesco Forconi et al. Blood 2009;114:4696-4702 ©2009 by American Society of Hematology