High fat diets lead to the production of bile acids, promoting colorectal cancer and high meat diets have increased N-nitroso compounds which are carcinogenic. Fruits and vegetables also contain antioxidants. Exercise is helpful since it decreases transit time of food and aspirin is also protective. Estrogen in birth control pills and hormone replacement therapy increases cancer risk. Also the earlier the time of birth of the 1st child, the less the risk.
Obesity is also a risk factor.
In these people, all cells carry the mutation yet cancer only in certain tissues - ex. RB1 gene and retinoblastomas. Suspect inherited cancer when a family has many members that develop rare cancer or if many members develop tumors at a young age or multiple 1 tumors. Some of the manifestations are different in inherited vs. somatic mutations - hereditary p53 mutation results in soft tissue sarcoma, brain tumor, leukemia and breast cancers while somatic mutation leads to lung and colon cancers. Whether or not a person develops a tumor depends upon dietary and environmental factors as well as other contributing genes.