The increased risk of cholangiocarcinoma in patients with congenital cystic disease of the biliary tree is well documented. The reason for the malignant transformation is taught to de related to chronic inflammation and bacterial exposure within bile ducts. Total excision of the choledochal cyst notably reduces the risk of cancer. Five to twenty percent of adult patients with unexcused cysts or treated with by pass will develop cholangiocarcinoma. We are presenting the case of a young female diagnosed with a choledochal cyst at age of four, treated with by pass procedure. Fourteen years later she presented with a severe angiocolitis, hemorrhage and malignant transformation within the cyst.