Cancer occurs when a cell or cells divide abnormally when they should not. Cells are the basic physical unit of life. Examples of red blood cells in the body cells, muscle cells (sometimes called muscle fibers), and bone cells ( osteocytes). Each Cell type can connect with another cell of the same type to form a body text. For example, a muscle cell or muscle tissue cells and nerve cells, called neurons, come together to form a nervous system.
Most of the body’s cells divide regularly to form new cells to replace dead or obsolete cells. This dividing process that a particular cell undergoes is called cell division. Cell division is important for tissue repair, organ growth, and even the whole person. However, some cells cannot divide and replace dead cells. For example, brain cells (neurons) cannot divide and replace dead cells. This is the reason why as people age, brain functions are not as good as they used to be.
But in cancer, cells divide when the body doesn’t need them, or they don’t die when they’re supposed to. These abnormally dividing cells can form a mass, referred to as a growth or tumor. Cancer cells can escape from the organ where it started and cause cancer in other parts of the body by traveling through the circulatory system and/or the lymphatic system. This spread of cancer is called metastasis.
A tumor can be either benign, that is not cancerous, or malignant, which is cancerous.
Benign tumors are not cancerous. But the abnormal cells are constantly dividing, so that the tumor grows and can be potentially dangerous if it compresses other nearby organs. Cells from benign tumors do not travel or spread to other parts of the body, so they grow locally. Most tumors are rarely life-threatening and usually can be. This type of tumor, once removed, rarely recurs. Examples of benign tumors include hepatic adenoma, which is a benign tumor of the liver’s hepatocytes, and lipoma—a benign tumor that occurs in fat cells (lipocytes).
Tumors are malignant cancers, often serious, and can be life-threatening. They can be taken away, but they can be reborn. Cells from malignant tumors can leave the organ in which they started and spread to other organs. Examples of a malignant tumor or cancer include lung cancer and colorectal cancer.
There are over a hundred types of cancer. Most common cancers are named after the organ in which they begin. For example, cancer that starts in the colon or other parts of the stomach is called stomach cancer or gastric cancer, and colon cancer is called cancer when it starts in any part of the colon. Cancer is sometimes named for the quality of the cell involved. Examples are basal-cell carcinoma and leukemia. squamous cell carcinoma is a type of cancer that begins in the basal cells of the skin. Leukemia, on the other hand, involves blood cells called leukocytes. Leukocytes is the medical term for white blood cells, immune cells.
Cancer is the most common cause of death worldwide, according to the World Health Organization (WHO). About 7.4 million deaths were caused by cancer worldwide in 2004. Each year the number of cancer-related deaths increases. The World Health Organization estimates that in 2003 there will be approximately 12 million deaths due to cancer.
Cancer treatment is much more effective if the condition is detected and treated in its early stages.
Sources:
US National Cancer Institute. Cancer Awareness Series: Cancer National Institutes of Health (NIH). http://www.who.int/mediacentre/factsheets/fs297/en/index.html (Accessed on October 19, 2009)
US National Cancer Institute (May 11, 2009). What is Cancer? National Institutes of Health (NIH). http://www.cancer.gov/cancertopics/what-is-cancer (Accessed on October 20, 2009)
World Health Organization (WHO) Media Center (Fact Sheet No. 297, February 2009).
