There are three major types of causes of rectal cancer, as follows: 1. the most common is the development from rectal adenoma, which is found to be genetically brought from birth, familial, and is a cytogenetic disease, genetically brought to be the main and most common cause of rectal cancer; 2. closely related to diet and living habits, such as most people like to consume too much animal protein and fat, while consuming less vegetables and fiber; 3. some rarer diseases, such as family inherited polyp disease, schistosomiasis, and ulcerative colitis developed from.