APC and colorectal carcinoma: Our results are consistent with several published research reports, showing evidence of APC being the most frequently mutated gene detected in early-onset CRC patients [19,22,23]. Further analysis of the immunohistochemical staining of the four main DNA mismatch-repair (MMR) genes, the microsatellite instability (MSI) testing, or MLH1 hypermethylation analysis, is required to confirm the diagnosis of the PMCRC9 patient.