1. From the Department of Pediatrics, University of Pavia, IRCCS Policlinico S. Matteo, Pavia, Italy; Department of Pediatrics, University of Milano, Ospedale S. Gerardo, Monza, Italy; Departments of Hematology-Oncology and Pathology and Laboratory Medicine, St Jude Children's Research Hospital, Memphis, TN; and the University of Tennessee, Memphis, College of Medicine, Memphis, TN.