Defining Cancer

At its heart, cancer is the result of uncontrolled cell growth. Our bodies are composed of trillions of cells, all working together. In cancer, one of those cells stops paying attention to the normal signals that tell cells to grow, stop growing or even to die. Cancer cells still share many of the same needs and properties of normal cells but they become independent of the controls that make our body function smoothly. The process by which a normal cell changes into one that behaves so abnornally can take a long time and is often triggered by outside influences.⁽¹⁾The next few sections describe the differences between normal and cancer cells and outline the steps leading to the creation of a cancer cell from a normal cell.

Cancer is actually a general term that describes a large group of related diseases.⁽¹⁾Every case of cancer is unique, with its own set of genetic changes and growth properties. Some cancers grow quickly while others can take years to become dangerous to the patient. The many differences between cases of cancer, even of the same organ (i.e. different cases of breast cancer), is one of the main reasons that treatment is so difficult.

Despite the differences between different types of cancer, all cancers DO share some common features,⁽²⁾ and these shared properties are the basis for many cancer treatments and research efforts. It is important to understand the basic, shared, features of cancer.  This will allow for an understanding of detection, diagnosis and treatment options.

Below is a list of the information found within this section. Click on one of the items or 'Next' to learn about the characteristics of cancer cells.

• The Hallmarks of Cancer
• Changes in Physical Properties of Cells
• Section Summary: Characteristics of Cancer Cells

You can also test your knowledge of the Hallmarks of Cancer with an educational game:

• Know the Flow: Hallmarks of Cancer

Characteristics of Cancer Cells

There are numerous changes that must occur for a normal cell to become a cancer cell.  Additional changes are needed for that single cell to form a tumor and then for that tumor to grow and spread.  An excellent review article detailing a model of cancer growth and spread was written by Douglas Hanahan and Robert Weinberg.⁽¹⁾ The information covered in the following pages is detailed in their paper. Click on the links below or 'Next Page' to learn more about the 'Hallmarks of Cancer'.

• Growth Without 'GO' Signals
• Failure to Respond to 'STOP' Signals
• Unlimited Number of Cell Divisions
• Avoidance of Cell Death
• Angiogenesis
• Tissue Invasion and Metastasis
• Physical Changes in Cancer Cells