PIK3CA and neoplasm: In all tumor samples of patients with or without a history of smoking and alcohol use, highest mutation rates were found in TP53, CDKN2A, PIK3CA, and HRAS. Mutation rates for TP53 were between 56 and 88%, for CDKN2A between 4 and 24%, for PIK3CA between 0 and 43%, and for HRAS between 2 and 21%.