High extreme values of B12 vitamin could be linked with high riskcáncer development throughout the DNA integrity distress because a cobalamine disfunctional metabolism. It's vital to understand the role of B12 vitamin as inespecific tumoral marker in the development of solid neoplasm when other many serious diseases as blood, liver and kidney diseases are rejected. We report a patient case about B12 hypervitaminosis and rectum cáncer (AU)