Cancer cells develop from the cells that line the colon or rectum. The cells can spread through the lymphatic system or the bloodstream. Colorectal cancer spreads most commonly to the liver and lungs.

The exact cause for colorectal cancer is unknown, but genetics may play a role.

Genes control the functions inside a cell. Special genes control how cells divide and grow. Cancer occurs when the damaged genes stimulate the cell to multiply out of control. The exact cause for this damage is unknown.

Examples:

• DNA
• Genes on chromosomes
• Cancer cells
• Cancer cell division