Mutations in the PIK3CA gene are found at similar frequencies in pure ductal carcinoma in situ, ductal carcinoma in situ adjacent to invasive ductal carcinoma (IDC), and in IDC, suggesting that PIK3CA mutations are key to shaping the tumor identity at the initial steps of tumorigenesis [61]. The gene discussed is PIK3CA; the disease is invasive ductal breast carcinoma.