The highest malignant potential is seen in:

"Colorectal cancer develops in 100% of untreated FAP patients often before the age of 30". Familial adenomatous polyposis (FAP) Autosomal dominant Numerous colorectal adenomas by teenage years. Mutation of adenomatous polyposis coli gene (APC). At least 100 polyps is necessary for diagnosis of classic FAP, High risk of causing colorectal cancer, Prophylactic colectomy is standard therapy Etiology Molecular defect Target gene Transmission Familial adenomatous polyposis APC/WNT pathway APC Autosomal dominant Hereditary nonpolyposis colorectal cancer DNA mismatch repair MSH2, MLH1 Autosomal dominant Sporadic colon cancer APC/WNT pathway APC None Sporadic colon cancer DNA mismatch repair MSH2, MLH1 None