Heredity reason for cancer
The vast majority of cancers are non-hereditary (sporadic). Hereditary cancers are primarily caused by an inherited genetic defect.
Less than 0.3% of the population are carriers of a genetic mutation that has a large effect on cancer risk and these cause less than 3–10% of cancer.
Some of these syndromes include certain inherited mutations in the genes BRCA1 and BRCA2 with a more than 75% risk of breast cancer and ovarian cancer, and hereditary nonpolyposis colorectal cancer (HNPCC or Lynch syndrome),
which is present in about 3% of people with colorectal cancer, among others.
Statistically, for cancers causing most mortality, the relative risk of developing colorectal cancer when a first-degree relative (parent, sibling or child)
