Can a hernia cause cancer?

No, but.. If you mean hiatal hernia (stomach pops up into chest): can increase backflow of stomach contents, which can increase esophagitis, which can cause pre-cancerous changes (barrett's esophagus), which can sometimes cause cancer, then yes, indirectly, and on occasion, hernias can cause cancer. Otherwise things like inguinal (groin) hernias do not cause cancer.
No. It is extremely unusual to associate hernias with cancer.