In the most basic terms, cancer refers to cells that grow out-of-control and invade other tissues. Cells become cancerous due to the accumulation of defects, or mutations, in their DNA. Certain:
- inherited genetic defects (for example, BRCA1 and BRCA2 mutations),
- environmental factors (for example, air pollution), and
- poor lifestyle choices — such as smoking and heavy alcohol use — can also damage DNA and lead to cancer.
Most of the time, cells are able to detect and repair DNA damage. If a cell is severely damaged and cannot repair itself it undergoes so-called programmed cell death or apoptosis. Cancer occurs when damaged cells grow, divide, and spread abnormally instead of self-destructing as they should.