Remarkably, PIK3CA mutations have been found in all human cancers and are especially predominant in endometrial, breast, and bladder cancers, as well as Klippel–Trenaunay syndrome, which is a condition under the umbrella of PIK3CA-related overgrowth spectrum diseases [17,18,19,20]. The gene discussed is PIK3CA; the disease is urinary bladder carcinoma.