Cancer is a disease that involves uncontrolled cell division caused by a genetic mutation. It can occur in almost any region in the body. So, cancer is essentially uncontrolled what of what?

Cancer is essentially uncontrolled mitosis of specialized cells.

Explanation:

As you said, cancer can control in any region of the body. As a matter of fact, a cancerous cell is produced in your body every 30 minutes and your immune system locates and kills it. Cancer is unpredictable and can happen in any specialized cell.

geologic time scale (for gradpoint) =)