The protein encoded by the proto-oncogene PTPN11 is acytoplasmic tyrosine phosphatase, which is widely expressed in most tissues andknown to play a regulatory role in normal hematopoiesis, and in mitogenicactivation, metabolic control, transcription regulation, and cell migrationsignaling pathways (Chan and Feng, 2007).Somatic PTPN11 mutations have been detected in juvenilemyelomonocytic leukemia, myelodysplastic syndromes and acute myeloid leukemia (Tartaglia et al., 2003; Chan and Feng, 2007). Here, PTPN11 is linked to myelodysplastic syndrome.