PIK3CA and cancer: Here, 41 short-term khat users carried seven somatic mutations in four out of nine cancer-related genes: 29/41(70.73%) ARID1A, 24/41(58.53%) MLH1, 34/41(82.92%) PIK3CA and 36/41(87.80%) TP53. The 42 long-term khat users incorporated nine somatic mutations in five out of nin ecancer-related genes: 40/42(95.23%) ARID1A, 36/42(85.71%) ARID2, 29/42(69.04%) PIK3CA, 27/42(64.28%) MLH1, and 35/42(83.33%) TP53. Every khat user had somatic mutations related to OSCC affecting the gingiva and the lower lip.