In tumors with concurrent RAS/BRAF and PIK3CA mutations, PIK3CA and RAS/BRAF mutant allele frequencies (MAFs) were highly concordant in dMMR tumors, whereas PIK3CA MAFs were significantly lower than the corresponding RAS/BRAF MAFs in pMMR tumors, implying that PIK3CA mutation may occur in the early stage of dMMR CRC. Here, PIK3CA is linked to colorectal carcinoma.