The term Familial Colorectal Cancer Type X (FCCTX) was proposed to define families with a strong CRC family history that meet the Amsterdam I criteria [3] where the tumors are DNA mismatch repair (MMR)-proficient/microsatellite stable and do not carry a germline pathogenic variant in one of the MMR genes (Lynch syndrome) [4, 5]. The gene discussed is MRC1; the disease is familial colorectal cancer type X.