Biliopancreatic diversion (BPD) has excellent results, with the average patient losing 60% to 80% of the excess weight in the first 2 years. However, the BPD works by malabsorption and malabsorptive problems may be experienced with the operation. Therefore, monitoring is necessary for life. In the recent literature there is some debate over the possibility that this technique can increase the risk of colon cancer secondary to the action of the unabsorbed food and bile acid on colonic mucosa. We report the case of a 42-year-old patient with a previous bariatric surgery (BPD with 50 cm common channel; 300 cm alimentary limb) who developed a very aggressive right colon cancer 6 years after the operation. We also review our series of 330 patients operated on during a 14-year period to try to answer if there is any relationship between BPD and colon cancer. Abdominal examination was normal and she also was complaining of fatigue and weakness. We ordered a complete blood test with vitamins and to our surprise we found a highly elevated CEA (334.6 ng/mL; normal 0-3 ng/mL), CA 19-9 levels (391.9 U/mL; normal 0-35 U/mL) and mild anemia secondary to iron deficiency (10.3 g/dL; normal 12-16 g/dL). Blood chemistry and vitamin levels were within normal range. An urgent CT-scan was