PIK3CA and small intestine carcinoma: First, our results showed that the genes commonly altered in small-bowel cancer in our Japanese population were TP53, KRAS, ARID1A, PIK3CA, APC, SMAD4, NOTCH3, CREBBP, PTCH1, and EP300. In previous reports from Western countries, the most commonly mutated genes identified in small-bowel cancer include TP53 (41%–58%), KRAS (27%–54%), APC (13%–27%), SMAD4 (10%–17%), and PIK3CA (9%–16%) [11, 13–15].