PIK3CA and head and neck squamous cell carcinoma: Although there is a lack of a clear consensus about the prevalence of mutated PIK3CA in cancers, a few recent studies with statistical analyses of the prevalence of PIK3CA mutations in cancers have shown that breast cancer has the highest mutation rate, followed by endometrial, bladder, colorectal carcinoma, and head and neck squamous cell carcinoma [37, 38].