Introduction to Cancer

The body is made up of several millions of living cells. Normal body cells grow, divide, and die in an orderly way. During the early years of a person's life, normal cells divide faster to allow the person to grow. After the person grows and become an adult, most cells divide mitotically only to replace worn-out, damaged, or dead cells.

Cancer begins when cells in  the body start to grow without control. There are several types of cancer, but all of them initiate because of this uncontrollable growth of abnormal cells.

Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells keep on growing and form new cancer cells. These cancer cells are invasive, something that normal cells cannot do. 

In most time, the cancer cells form tumours. But some cancers, like leukaemia, rarely form tumours. Instead, these cancer cells are embedded in the blood and bone marrow. 

When cancer cells get into the bloodstream or lymph vessels, they can travel to the whole body. Then they begin to grow and form new tumours that replace normal tissue. This process is called metastasis. 

No matter where a cancer may spread, it is always named for the place where it initiated. For example, breast cancer that spread to the liver is still called breast cancer, not liver cancer. Likewise, prostate cancer that has spread to the bone is called metastatic prostate cancer, not bone cancer.

Different types of cancer behave differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That is why people with cancer need treatment that is specified for their own kind of cancer. 

Not all tumours are cancerous. Tumours that are not cancer are called benign. Benign tumours can cause problems – they can grow very large and exert pressure on healthy organs and tissues. But they cannot grow into other tissues. Because of this, they also can't spread to other parts of the body. These tumours are usually not life threatening.