Many of us develop calluses at one point or another, but for some people calluses and corns can become severe and highly inconvenient. In some rare cases, extreme thickening of the skin is a symptom of a particular form of esophageal cancer. New research investigates the link between foot calluses and cancer of the esophagus in mice and humans.
http://www.medicalnewstoday.com/articles/315669.php
How are calluses and throat cancer related?