Is cancer genetic?

Is cancer genetic?
 
Does cancer run in families?
Yes, the fact that cancer can run in families has been recognized for over a century. Inherited cancer syndromes, usually involving mutations in tumor suppressors or DNA repair genes, may account for up to 4% of all cancers. 
 
Cancer due to inherited abnormal genes is rare:
Clear inheritance of cancer occurs in rare types of familial cancer syndromes.
  • An example is retinoblastoma (cancer of the retina) which usually affects young children. When a child inherits the abnormal gene from one of the parents, the disease will affect both eyes at a young age. It seems that all cells in the retina carry this genetic abnormality, making the likelihood of cancer very high.
  • However, genetic predisposition is still not very clear in most common types of cancer.