Somatic PTPN11 mutationsalso occur in childhood myelodysplastic syndromes, acute monocyticleukemia (AMoL, FAB M5), and acute lymphoblastic leukemia (ALL, “common”subtype).3,4 More rarely, activating mutations in thisgene are found in adult myelodysplastic syndromes, chronic myelomonocyticleukemia, and solid tumors, including neuroblastoma, glioma, embryonalrhabdomyosarcoma, lung cancer, colon cancer, and melanoma. Here, PTPN11 is linked to acute lymphoblastic leukemia.