A group of autosomal-dominant inherited diseases in which COLON CANCER arises in discrete adenomas. Unlike FAMILIAL POLYPOSIS COLI with hundreds of polyps, hereditary nonpolyposis colorectal neoplasms occur much later, in the fourth and fifth decades, due to heterogeneous gene mutations linked mostly to chromosomes 2, 3, and 7. These defects allow rapid progression from adenomas to carcinomas.