We reported earlier that PIK3CA mutations frequently coexist with other PI3K-activating alterations in breast (with HER2 and HER3) and endometrial cancers (with PTEN and K-Ras), and that mutant p110α combined with mutant Ras efficiently transformed immortalised human mammary epithelial cells (Oda et al, 2005, 2008). Here, PIK3CA is linked to endometrial cancer.