What Is Cancer and How Does It Develop?

Cancer is not a single disease but a collection of more than 100 distinct diseases united by one defining feature: the uncontrolled growth and spread of abnormal cells. It is the second leading cause of death in the United States after heart disease, responsible for approximately 600,000 deaths annually, yet it is also one of the most successfully treated serious diseases when detected early. Understanding how cancer develops — at the cellular and molecular level — demystifies the diagnosis and informs everything from prevention to treatment.

The Normal Cell Cycle And Its Controls

To understand cancer, you must first understand how normal cell division is regulated. The body contains approximately 37 trillion cells, most of which divide — skin cells every few weeks, gut lining cells every few days, blood cells continuously. This division is precisely controlled by:

Proto-oncogenes: Genes encoding proteins that promote cell growth, proliferation, and survival. They are the accelerator of the cell cycle. Examples: RAS, MYC, HER2, EGFR, BCL-2.