Colon cancer and rectal cancer are grouped under the name of colorectal cancer. The tumor grows from cells that line the inner wall of the colon or rectum, usually by gradual transformation of a benign tumor into malignant (cancerous) growth. It is a common health problem in many countries worldwide, and affects, mostly, people with high risk factors. Please see colorectal cancer causes and risk factors for more information…
Colorectal cancer is characterized by an abnormal proliferation of a group of belligerent cells in the large intestine and the formation of glandular carcinoma (a cancer arising in the epithelial tissue of the lining of the internal colon or rectum) or adenocarcinoma (a cancer developing in mucus-secreting glands throughout the colorectal tissue).
Without a proper treatment to stop it, the tumor will eventually penetrate deeply and can successively affect different layers of the colonic mucosa to the peritoneum, a serous membrane lining the cavity of the abdomen and covering the abdominal organs. As the disease progress, other organs, such as the lymph nodes, will be invaded by cancerous cells. This growth is possible either by lymph flow or bloodstream. An early diagnosis and effective colorectal cancer treatment are vital to avoid more serious complications.
Colorectal cancer is more common in men aged 65 years or more and very rare before the age of 50; except rare exception of familial cases. In addition, food seems to play certain role in its occurrence. For example, studies show that a diet high in unhealthy fat and animal protein and low in fiber may contribute to the occurrence of this disease.
After lung cancer in men and breast in women, colorectal cancer is particularly the third most common form of malignant tumor diagnosed in Western countries such as United States. In fact, this is the most common digestive cancers in nonsmokers in most developed countries such as France, Canada, United States, and Germany. Even when all necessary therapeutic procedures are taken, most colorectal cancer treatment options do not lead to good prognosis, making the disease one of the deadliest malignant tumors.
Large Intestine (Colon or the Large Bowel)
Forming the last part of the digestive system, the colon and rectum are called the large intestine or large bowel. It (the large intestine) measures 1 to 1.5 meter (5 feet) long and 4 to 8 cm in diameter.
This is an important organ consists of several parts: the cecum (or caecum), which is the beginning of the large bowel; the ascending colon (right), the segment of the colon located between the cecum and the transverse colon; the transverse colon, the longest segment of the large intestine located between the ascending colon and descending colon; the descending colon (left), the part of the large intestine which transports feces from the transverse colon to the sigmoid colon; sigmoid colon (pelvic colon), the S-shaped segment of the large intestine; and the rectum, the final portion of the large intestine, terminating at the anus.
The main role of the large intestine is to eliminate waste, absorb water, maintain fluid balance and absorb certain vitamins. To function properly, it produces many bodily fluids, the chyle for instance. Chyle, producing by the small intestine, consists of lymph and emulsified fats, or free fatty acids (FFAs). It mixes within the colon with the mucus and intestinal bacteria to form fecal matter. Bacteria capable of digesting fibers (non-pathogenic bacteria) form new molecules that the colon is then able to assimilate.
Of 100 cases of colorectal cancer, about 40% affect the rectum and 60% the colon. Between 60 and 80% of colorectal cancers develop from preexisting colon polyps or adenomas. The risk of transformation of a polyp to cancer varies according to the size and composition of its cells. The lifestyle (eating habit, environment…) of the individual also plays an important role.
Colorectal cancer develops first locally, and then the cancer cells may migrate into other parts of the body through the bloodstream and lymphatic system to form other cancers, metastases. The most common metastatic colorectal cancers tend to be localized in the liver and lungs.