What is cancer?

What is cancer?

Cancer is not just one disease; there are more than 200 types of cancers which can occur on or in any part of the body. Our bodies consist of trillions of cells. All parts of the body including blood, bones, organs, muscles, tissues, and skin are composed of cells. Normal cells are constantly reproducing by dividing and multiplying to replace old and damaged cells. Normal cells grow and die and are replaced by new cells in an orderly fashion. When the orderly reproduction of cells becomes out of control and reproduce in an abnormal fashion, excess cells that are formed are known as a tumor. In most of the cases, a tumor is “benign” and not life-threatening. Benign tumors are not cancer. However, sometimes when these cells begin to divide and multiply, they can become cancer cells forming “Malignant Tumors”.



Spread of cancerous cells

Cancerous cells have the ability to invade other tissues. Malignant tumors, unlike benign tumors, effect and destroy nearby organ(s). Eventually cancer cells break off through the blood or the lymphatic system to produce new tumors in other parts of body. This process of spreading is medically called “metastasis”. Metastasis may last as short as a few weeks to as long as several years. If the cancer cells are left untreated, they will eventually invade and spread and destroy the organ that was originally affected as well as organs to which the cancer cells have spread and have become metastasised.

At the molecular level, how do cancerous cells start to divide?

Cancer begins when abnormal cells start to divide out of control. These cancerous cells will not die; instead they will continue dividing and growing until they start to invade other tissues. There are two characteristics that must exist in any cell to in order for it to be called a cancerous cell:
1) Out of control cell growth and division,
2) The ability to invade other normal tissues.
Basically, the defect is in the DNA of the cells. DNA is the guide to the cellular life cycle. In normal cells, if the DNA becomes damaged for any reason, the cell will try to repair itself. If it fails to do so, it will begin a process of killing itself. However, cancerous cells can neither repair the damaged DNA, nor can they die by themselves.

What causes the DNA damage?

Normal cells grow and divide in a normal pattern, then die and replaced by new cells. The life cycle of normal cells is under control. Once there is a defect in this life cycle, the cells will divide at a faster rate than usual due to the loss of the normal body control; those abnormal cells are called cancerous cells. The most common cause of damage to cells is by accident during the normal cell cycle. Environmental factors, such as cigarette smoking and alcohol consumption have a great influence. Unfortunately, no exact reason is known for cancer yet.

Spread of cancerous cells

Cancerous cells have the ability to invade other tissues. When they invade the blood or the lymph nodes, they will spread throughout the body to grow elsewhere in the body forming new tumors; this process is known medically as “Metastasis”.

Different types of cancer

The cancer is given the name to coincide with the part of the body where the cancerous cells first developed. For instance, if breast cancer spreads to the liver, it is named medically “metastatic breast cancer”, not “liver cancer”. Each type of cancer behaves uniquely; thus the treatment depends on the type of cancer and the different factors involved.

Not all tumors are cancer!

The term “tumor” is quite different from the term “cancer”. Actually cancer is a type of tumor, but not all tumors are cancer! Tumor is a term used to describe abnormal growth of cells. However, tumor cells may have either the ability to invade other tissues which are called “cancer”, or they do not have the ability to invade other tissues in which case, they are called “benign tumors”. Benign tumors are never life-threatening because they can’t metastasize to other parts of body.