There are many reasons why a human cell can go crazy and begin to multiply uncontrollably until generating a malignant tumor. Smoking, for example, causes mutations that can lead the cell to reproduce without restraint. Alcohol, excessive exposure to the sun or simply chance can also favor these errors in cell replication. Age has always been, however, the most important variable: the older you are, the greater the risk of these errors occurring because cells degrade, control mechanisms are lost and the defense system deteriorates. However, for some time now, something has been changing in the traditional spread of the disease: age continues to be a determining factor, but increasingly there are more cases among young adults and the causes are not clear.