3. Health conditions
Certain health conditions increase the risk of certain types of cancer. For example, chronic hepatitis viruses cause severe liver injury, cirrhosis, and liver cancer. Infection by the bacteria H. pylori has been known to trigger stomach cancer by different mechanisms. Other conditions that trigger or facilitate cancer include ulcerative colitis, HIV, colon polyps, and others.
4. Family history
In some families, there is a higher risk of cancer due to genetic susceptibilities or inherited mutations. In some cases, cancers develop in intrauterine life or closely after being born due to severe mutations.