My grandfather had non hodgkin lymphoma in the stomach and my father had adenocarcinoma in the stomach. Can this be genetic-do I or my sister have a higher chance of suffering from stomach cancer? Are these two cases related? We are vegetarian. Could it be due to some dietary reason? My grandfather use to smoke and chew tobacco but my father was a teetotaler but obese. How did my father get the more aggressive form of cancer?