Predisposition for early-onset, hereditary, nonpolyposis (usu. right-sided) colorectal carcinoma; type 1 is site specific and type 2 is associated with other adeno-carcinomas (i.e., stomach, breast, ovary, endometrium). Condition is autosomal dominant and is associated with DNA mismatch repair genes MSH2, MLH1, PMS1, and PMS2. Surveillance colonoscopy should begin at 25 years of age. Surgical treatment for index cancer is subtotal colectomy. Carcinoma has better prognosis, stage-for-stage, than sporadic, colorectal cancers.