By Dr Ananya Mandal, MD
Cancer encompasses over 100 diseases. There are several types of cancers depending on the organ they affect, however, they possess the same common properties of:
abnormal cell growth
capacity to invade other tissues
capacity to spread to distant organs via blood vessels or lymphatic channels (metastasis)
Untreated cancers can cause serious illness by invading healthy tissues and lead to death.
How does cancer occur?
The body is made up of trillions of living cells. These cells grow, divide, and die in an orderly fashion. This process is a tightly regulated one that is controlled by the DNA machinery within the cell. When a person is a baby or a child or within his or her mother’s womb, cells divide rapidly to allow for growth. After the person becomes an adult, most cells divide only to replace worn-out or dying cells or to repair injuries.
When cells of the body at a particular site start to grow out of control, they may become cancerous. Cancer cell growth is different from normal cell growth. Instead of dying, cancer cells continue to grow and form new, abnormal cells. In addition, these cells can also invade other tissues. This is a property that normal cells do not possess.
Molecular pathology behind cancer
Cancer cells originate from normal cells when their DNA (deoxyribonucleic acid) or blue prints within the cell nucleus is damaged. DNA is in every cell and it directs all the cell’s actions, growth, death, protein synthesis etc. When DNA is damaged in a normal cell, the cell either repairs the damage or the cell dies.
In cancer cells, the damaged DNA is not repaired, and the cell does not die. Instead it gives rise to more such abnormal cells with abnormal DNA. These new cells all have the same defective DNA of the original cancer cell.
DNA damage may be inherited from parents or may be a spontaneous problem that occurs during the lifetime of a person. DNA damage may also be triggered by exposure to certain environmental toxins such as those present in cigarette smoke. There are, however, multiple factors that may cause cancer and it is difficult to pin point an exact cause.
Cancerous and benign tumors
As the cells proliferate they may form tumors. Not all of these tumors are cancerous. Those that are not cancerous are called benign tumors. And those that are, are called malignant tumors.
Benign tumors can grow very large and press on healthy organs and tissues. However, they do not invade other organs or spread via blood or lymphatic channels. These tumors are almost never life threatening.
Who gets cancer and how common are cancers?
There are millions of people worldwide who are living with cancer or have had cancer. According to estimates, around half of all American men and one third of all American women will develop cancer during their lifetimes.
A healthy lifestyle with regular physical activity, healthy diet, maintenance of healthy weight and staying away from tobacco, sun exposure and other known cancer causing substances can help reduce the risk of getting cancers.
Some cancers also have effective screening tests. This helps in detection of common cancers as early as possible. Early treatment often means better chances of recovery and response to anti cancer therapy. Common examples of this are breast cancer and colon cancer screening that saves thousands of lives each year.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)