1 Center for Cancer and Blood Disorders, Children's National Hospital, Washington, District of Columbia, USA.
2 Department of Pediatrics, The George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA.
3 Division of Pathology and Laboratory Medicine, Children's National Hospital, Washington, District of Columbia, USA.
4 Departments of Pathology and Pediatrics, The George Washington, University School of Medicine and Health Sciences, Washington, District of Columbia, USA.