1. National Pediatric Oncology Unit; Guatemala City Guatemala
2. Francisco Marroquín Medical School; Guatemala City Guatemala
3. Department of Medicine and Surgery, Center of Biostatistics for Clinical Epidemiology; University of Milano-Bicocca; Monza Italy
4. Flow Cytometry Laboratory (Dr. Rodolfo Lorenzana); Guatemala City Guatemala
5. Department of Oncology; St. Jude Children's Research Hospital; Memphis Tennessee
6. International Outreach Program, St. Jude Children's Research Hospital; Memphis Tennessee
7. Department of Pediatrics; University of Milano-Bicocca, Monza and Brianza Child and Mother Foundation (MBBM), San Gerardo Hospital; Monza Italy