Cancer is a generic term used to describe a group of diseases that develop across time and can affect any part of the body. There are more than a hundred distinct types of cancer, which vary substantially in their behavior and response to treatment. Globally, cancer is the second leading cause of death and accounts for 9.6 million deaths in 2018.
As the cancer burden continues to grow globally, the prevention of cancer is one of the most significant challenges of the 21st century. To understand any cancer type and to manage it effectively, it is first important to understand about cancer.
What is cancer?
Humans are complex multicellular organisms made up of trillions of cells, each with its own structure and function. And our body is programmed to routinely replenish cells in different organs. As normal cells age or get damaged, they die off and new cells take their place as per the signals given by the genes.
Cancer begins when these genetic changes interfere with this orderly process. When this process is disturbed cells no longer respond to the signals and begin to grow abnormally. These abnormal cells grow and divide uncontrollably in the body and slowly accumulate to form a tissue mass, lump or growth called a tumor. These abnormal cells can destroy normal body tissue and spread through the bloodstream and lymphatic system.
Types of cancer
Cancers are mainly divided into five types based on where it begins:
- Carcinomas develop in the skin or tissues that line the internal organs
- Sarcomas begin in the bone, cartilage, fat, muscle or other connective tissues
- Leukemia begins in the blood cells and bone marrow
- Lymphomas begins in the lymphatic system
- Central nervous system cancers develop in the brain and spinal cord
What causes cancer?
What causes cancer?
The exact cause of cancer is still unknown, but researchers believe that it is caused by sudden mutations (changes) in the DNA. These changes may be due to some environmental agents, viral or genetic factors.
Gene mutations and cancer
Every cell in the human body contains a chemical substance called DNA, which is packaged into a large number of individual genes. These genes regulate the growth, development and functioning of the cell. When mutations occur in these genes:
- Old cells or damaged cells continue growing and accumulating
- New cells develop faster
Mutations are any changes in the DNA of a cell caused by aging, exposure to chemicals, radiation, hormones or other factors in the body and the environment. Over time, when these mutations occur more frequently in a single cell, it will divide and grow in a way that becomes cancer.
What are the risk factors for cancer?
According to the World Health Organization (WHO), common risk factors for cancer include:
- Tobacco use
- Alcohol use
- Chronic infections from helicobacter pylori, hepatitis B virus (HBV), hepatitis C virus (HCV) and some types of human papillomavirus (HPV)
- Environmental and occupational risks including ionizing and non-ionizing radiation
- Overweight and obesity
- Physical inactivity
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