What is cancer?
Cancer is a group of more than 100 different diseases. They affect the body’s basic unit, the cell. Cancer occurs when cells become abnormal and divide without control or order. Like all other organs of the body, the colon and rectum are made up of many types of cells. Normally, cells divide to produce more cells only when the body needs them. This orderly process helps keep us healthy.
If cells keep dividing when new cells are not needed, a mass of tissue forms. This mass of extra tissue, called a growth or tumor, can be benign or malignant.
Benign tumors are not cancer. They can usually be removed and, in most cases, they do not come back. Most important, cells from benign tumors do not spread to other parts of the body. Benign tumors are rarely a threat to life.
Malignant tumors are cancer. Cancer cells can invade and damage tissues and organs near the tumor. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or lymphatic system. This is how cancer spreads from the original (primary) tumor to form new tumors in other parts of the body. The spread of cancer is called metastasis.
When cancer spreads to another part of the body, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if colon cancer spreads to the liver, the cancer cells in the liver are colon cancer cells. The disease is metastatic colon cancer (it is not liver cancer).
What is cancer of the colon and rectum?
The colon is the part of the digestive system where the waste material is stored. The rectum is the end of the colon adjacent to the anus. Together, they form a long, muscular tube called the large intestine (also known as the large bowel). Tumors of the colon and rectum are growths arising from the inner wall of the large intestine. Benign tumors of the large intestine are called polyps. Malignant tumors of the large intestine are called cancers. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can be easily removed during colonoscopy and are not life-threatening. If benign polyps are not removed from the large intestine, they can become malignant (cancerous) over time. Most of the cancers of the large intestine are believed to have developed from polyps. Cancer of the colon and rectum (also referred to as colorectal cancer) can invade and damage adjacent tissues and organs. Cancer cells can also break away and spread to other parts of the body (such as liver and lung) where new tumors form. The spread of colon cancer to distant organs is called metastasis of the colon cancer. Once metastasis has occurred in colorectal cancer, a complete cure of the cancer is unlikely.
Globally, cancer of the colon and rectum is the third leading cause of cancer in males and the fourth leading cause of cancer in females. The frequency of colorectal cancer varies around the world. It is common in the Western world and is rare in Asia and Africa. In countries where the people have adopted western diets, the incidence of colorectal cancer is increasing.
Viruses and Liver Cancer (Perspectives in Medical Virology) (Hardcover)
M. Colombo
…an excellent source of referenced information on the biology of liver cancer for hepatologists.
Digestive and Liver Disease
Hepatocellular carcinoma (HCC) is one of the most important complications of chronic viral hepatitis. It usually results in a fatal outcome if not discovered in its earliest stages. Its close association with the hepatitis B and C viruses makes it one of the first human cancers for which there is strong evidence of a viral cause. For this reason it provides a model for studying viral carcinogenesis in humans.
In some countries, HCC is one of the most common tumors of adult men. In addition, there is evidence that the incidence of this cancer has doubled in the past 15 to 20 years in many countries, and the incidence has doubled every 20 years for the past half century in Japan. In some studies, the increase has been shown to be due primarily to cases associated with HCV infection.
Molecular studies of HCC show that mutations in oncogenes, in various cellular repair pathways, and in tumor suppressor genes together appear to contribute to the development of this cancer. In HCCs associated with hepatitis B virus, the virus itself can interact with tumor suppressor proteins and other cellular signals in ways that probably permit HCC to develop even when there are no mutations in the genes for these signals.
Viruses and Liver Cancer (Perspectives in Medical Virology) (Hardcover)
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