5 first identified Shp2 as a major phosphorylation site in response to platelet-derived growth factor (PDGF). Since then, many stimuli, including some cytokines and growth factors, have been found to activate Shp2. Ptpn11 is also the first identified proto-oncogene that encodes a tyrosine phosphatase 6 and it has been extensively investigated in the field of cancer. Ptpn11-related phosphatase activity is implicated in the regulation of intracellular signalling activity 7–9. This evidence concerns the gene PTPN11 and cancer.