The patient was referred for genetic counseling, and molecular genetic testing was performed using Illumina Miseq next-generation sequencing technology with targeted sequencing of colorectal-cancer-related genes (MLH1, MSH2, MSH6, PMS2, EPCAM, APC, MUTYH, STK11, SMAD4, BMPR1A TP53, NTHL1, POLE, POLD1, MSH3) included in the TruSight Cancer panel, complemented by bioinformatic analysis. The gene discussed is MLH1; the disease is colorectal cancer.