V-3, a 6-year-old child, warrants attention as WES revealed EpCAM, MSH2, PMS2 and APC co-mutations along with large deletions in EpCAM (exons 8–9) and MSH2 (exons 1–16), paralleling his father’s CRC tissue and suggesting possible germline mosaicism. Here, PMS2 is linked to colorectal carcinoma.