PIK3CA and colorectal carcinoma: Co-occurrence and mutual exclusivity analysis of MSS CRC samples identified four significant (P < 0.01) co-occurrent gene pairs (KRAS/PIK3CA, ARID1A/MTOR, KMT2C/ATM and SMAD4/BRAF) and three significant (P < 0.01) mutual exclusive gene pairs (APC/BRAF, KRAS/BRAF and TP53/PIK3CA) in the recurrent mutated oncogenes and tumour suppressor genes (Fig. 1d).