Several biomarkers are currently in use to provide a more comprehensive assessment of tumours in colorectal cancer, such as carcinoembryonic antigen (CEA), mismatch repair deficiency (MMR), microsatellite instability (MSI), v-raf murine sarcoma viral oncogene homolog B1 (BRAF), reticular activating system (RAS) mutations and caudal-type homeobox transcription factor 2 (CDX2) [6,7]. The gene discussed is CEACAM5; the disease is colorectal cancer.