What is Cancer

What is Cancer?

Cancer is a group of diseases that involve abnormal cell division and growth, and have the potential to invade and spread into other parts of the body.  The body is made up of trillions of cells.  These normal, healthy cells have a finite, programmed life and as they grow old or are damaged, they are replaced in an orderly way by surrounding cells that divide and grow to take their place.  Cancer develops when this orderly process breaks down. 

Cancerous cells can keep dividing and growing in an uncontrolled and disorderly way.  They lose respect for adjacent cells and healthy tissues, and can invade and spread to areas where they should not be.  This disrupts the function of normal healthy cells and tissues.


What causes cancer?

All cellular function is ultimately controlled and regulated by the molecule known as DNA.  DNA is a slightly unstable molecule that at all times, in normal healthy cells, undergoes little changes and disruptions and breaks.  The body has mechanisms to identify and repair any abnormality in the DNA, to allow the cell to resume normal function.  Sometimes the abnormality in the DNA is so great that the cell dies.  Sometimes the abnormality in the DNA is such that the change is not repaired and persists within the cell.  Rarely, if several of these changes are not repaired, the behaviour of the cell can be altered to become cancerous.

Most cancers are caused by “bad luck” and the accumulation of changes in the DNA that ultimately change the behaviour of the cell into a cancer.   Some environmental influences can increase the likelihood of accumulated cancerous change in the DNA, such as ultraviolet light, cigarette smoke, radiation and certain viruses.  Sometimes, there can be inherited genetic changes that can predispose to the development of cancer, such as the BRCA 1 and 2 gene mutation and Lynch Syndrome.


What does cancer look like?

Cancers typically do look different from surrounding normal tissue.  Typically cancers will be irregular, hard and sometimes ulcerated.  On occasion abnormal blood vessels are visible over the surface and feed into the growth.  Under the microscope there are characteristic appearances that allow us to make a definitive diagnosis.  The molecular genetics of cancer is typically quite different from normal healthy cells.              

Figure 1.  A highly magnified view of a dividing lung cancer cell (Credit: National Institute of Health (NIH))