Somatic mutations in PIK3CA have been found in 10--30% of colorectal cancers. KRAS, NRAS, BRAF and PIK3CA and non-functional PTEN predict resistance to anti-EGFR therapies in metastatic colorectal cancer. Recent 'molecular pathological epidemiology' (MPE) research has shown that aspirin use may be associated with better prognosis and clinical outcome in PIK3CA-mutated colorectal carcinoma, suggesting somatic PIK3CA mutation may be a molecular biomarker that predicts response to aspirin therapy. The R88Q mutation falls within the ABD domain of the p110a catalytic subunit and has been shown to result in gain-of-function in vitro. PIK3CA may be a target of directed therapy in some clinical settings.