Colon Tumor.

When polyps are found to be adenomas, it is important to remove them upon detection. In fact, it is often said that the war on large bowel cancer can best be fought by eradicating large bowel adenomas.

A small cancer of the large bowel may be present for a long time, even years, without producing symptoms. This is why screening for occult, or hidden, blood in the stool is such a valuable detection measure since this test is capable of identifying a large percentage of people who should be given further tests for possible large bowel cancer.

As the cancer grows, the growth patterns and symptoms tend to vary in different areas of the large bowel. On the right side of the colon near the end of the small intestine, the cancers tend to grow into the space within the bowel. Because die colon channel is larger in the cecum and ascending colon, cancer in these locations may become large enough to produce pain on the right side and to be felt upon examining the abdomen with the hand. These colon cancers also are well known to cause bleeding. Any older patient, particularly a person with an unexplained iron-deficiency anemia  a kind of anemia that is almost always caused by a slow, imperceptible loss of blood should be examined for possible right-sided colon cancer. A chemical test for hemoglobin the oxygen-carrying molecule in the blood—as well as a test for occult or hidden blood should be performed on all such patients. If these are positive, further investigations such as colonoscopy should be performed.
The channel on the left side of the colon is narrower than that on the right, and cancer in this area has a tendency to grow around and encircle the bowel wall. For this reason, left-sided colon cancer characteristically narrows or constricts the bowel channel, causing partial blockage of flow through the intestine. The main symptom of partial colon blockage is increasing constipation, often with bloating and gaseous distention of the abdomen. Cancers in the left colon also may cause bleeding, but anemia is less severe than it is in right-sided colon cancer.

The rectum—the lowermost four inches of the colon has a larger channel (the ampulla) than the rest of the large bowel. Cancer in the rectum commonly produces diarrhea that often contains blood. In part the diarrhea is spurious, or false, because the tumor in the rectal wall gives the patient the constant sensation of incomplete stool evacuation, resulting in repeated, unnecessary attempts to move the bowels.

Of all patients who develop large bowel cancer, about 85 percent have what is called "sporadic" cancer, meaning that, except for the presence of large bowel adenomas in some, there is nothing unusual about their health background. In contrast, in the remaining 15 percent there are identifiable risk factors that signal a possible predisposition to the dis-
Ulcerative colitis, for example, is one of these predisposing factors that may lead to a higher frequency of bowel cancer. About one of every hundred patients with large bowel cancer has a background of chronic ulcerative colitis that has not been treated by removal of the bowel. The risk of large bowel cancer is greatest among those patients whose colitis began at an early age, has been active for more than ten years, and involves the entire large bowel. In contrast, colitis patients who have had only a transient episode of ulcerative proctitis, limited to the rectum, do not have a higher incidence of large bowel cancer. Patients with chronic ulcerative colitis should have regular colonic examinations that include endoscopy, even if there are no symptoms. During endoscopy, a flexible fiberoptic instrument with special lights is inserted into the large bowel, enabling the doctor to examine the entire organ and, if necessary, remove small amounts of tissue for biopsy. This permits doctors to identify those patients who have abnormal cell activity at an early, even precancerous, stage. Surgery at this stage will prevent the later development of cancer.

About one of every hundred patients with large bowel cancer has a family background of polyps (familial polyposis) in the large bowel. Familial polyposis, also known as Gardner's syndrome, is equally common in men and women, and the children of an affected parent have a 50 percent chance of inheriting the disease. A person with this condition can develop hundreds or even thousands of adenomas in the large bowel, usually beginning in adolescence. If the colon is not removed, these patients almost always develop large bowel cancer before the age of forty. Some have other medical problems, including cysts and fatty tumors (lipomas) beneath their skin and in their bones, particularly in their jawbones. If these cysts or lipomas occur in a young person, they should serve as a warning that the large bowel should be examined for the presence of precancerous polyps.

About 10 to 15 percent of all patients with large bowel cancer will not have polyposis themselves, but will have one or more close relatives who have had large bowel cancer. The nature of inheritance in these families is not as well understood as it is in those with familial polyposis. When this kind of family background is present, the characteristics of the large bowel cancer tend to be different: the patient is likely to be younger and the cancer is more likely to arise in several places on the right side of the colon. Additional adenomas are commonly, but not always, present. Still, adult members of such families should be watched closely, even if they do not have symptoms pointing to disease or cancer of the large bowel because of the increased risk of developing the disease.