As PIK3CA mutations may affect different targets in the PI3K signaling pathway, we investigated these mutations in relation to several molecular markers known to be associated with PI3K pathway activation or to poor prognosis in endometrial cancer (Supplementary Table S5); including protein expression of Stathmin, p85α and PTEN (immunohistochemistry; IHC), KRAS mutations, PIK3CA amplification (assessed by Fluorescent in situ hybridization; FISH) or PIK3CA mRNA expression (Agilent microarray)7, 11, 24, 27, 30. Here, PIK3CA is linked to endometrial cancer.