PTPN11 and Osteochondroma: However, Wang et al.16 observed osteochondromas in Col2a1-CreER;Ptpn11Ex11fx/fx mice and both osteochondromas and enchondromas in Agc1CreER;Ptpn11Ex11fx/fx mice when SHP2 inactivation was induced in adulthood (8 weeks).93 Inconsistency between the results of these studies may be attributed to variations in tamoxifen administration regimens or to differences between the residual SHP2 proteins resulting from Ex4 or Ex11 deletions.