According to the American Cancer Society, colorectal cancer is one of the leading causes of cancer-related deaths in the United States. In fact, colorectal cancer is the third most common cancer diagnosed in both men and women in the U.S. (excluding skin cancers). The good news is that early diagnosis of colorectal cancer often leads to a cure; there are now more than 1 million survivors of colorectal cancer in the United States. To better understand the causes, risks and symptoms of colorectal cancer, let's first investigate what colorectal cancer is and what parts of the body this cancer affects.
What is cancer?
Cancer begins in the cells. Normally, the body forms new cells as needed, replacing old cells that die. Sometimes cell development goes wrong and either new cells grow when they are not needed or old cells don't die when they should. Doctors aren't sure of exactly what causes overgrowth of cells, however, extra cells form into masses called "tumors". Malignant tumor cells (cancer) can then invade nearby tissues or break away and spread to other parts of the body spreading cancer. If the cancer is allowed to grow, it eventually will invade and destroy nearby tissues and then spread farther.
What is colorectal cancer?
Most cancers are named for where they start. Colorectal cancer is a term used to refer to cancer that starts in either the colon or the rectum. Colon cancer and rectal cancer have many features in common, one of which is that they are both slow-growing cancers and they both take a long time to develop. Colorectal cancer spreads first to nearby lymph nodes. From there it may move to other parts of the body such as the liver, lungs, and less often, to the bones and the brain.
Types of Colorectal Cancer
Adenocarcinomas - Adenocarcinomas are the most common type of colon cancer and originate in glands of the intestinal mucosa, and are classified as either "mucinous" or "signet-ring cell".
Leiomyosarcomas - This type of colon cancer occurs in the smooth muscles of the colon wall. Leiomyosarcomas account for less than two percent of all colorectal cancers and have a fairly high chance of metastasizing.
Lymphomas - Colorectal lymphomas such as Non-Hodgkin's lymphoma are rare and tend to originate in the rectum rather than in the colon. However, lymphomas that originate elsewhere in the body are more likely to spread to the colon than to the rectum.
Melanomas - This type of colon cancer is rare and usually results the spread of a melanoma from another part of the body to the colon or rectum.
Neuroendocrine tumors - Neuroendocrine tumors are divided into two main categories: aggressive and indolent. Large cell and small cell neuroendocrine tumors are considered aggressive, while carcinoid tumors are considered indolent.
Click here for more on what causes colon cancer.