Colon cancer is a malignancy of the colon, or large intestine, a shallow digestive tube extending from the cecum to the rectum. In most cases, colon cancers begin as polyps, which are growths--clinically known as adenocarcinomas--projecting from the glandular epithelium that lines the colon's inner wall, according to the National Cancer Institute. Adenocarcinomatous tumors secrete mucus and other lubricating fluids.
Bleeding
Discharging bloody stools from the anus may be a worrying sign of colon cancer. Blood can sometimes make stools appear blackish. In general, rectal bleeding isn't severe, so it may remain undiagnosed for a long time. Iron-deficiency anemia can occur when a small amount of blood is lost on a regular basis. People with anemia may appear pale and may be tired all the time. Severe rectal bleeding is a very uncommon but life-threatening symptom.
Bowel Symptoms
An unexplained change in bowel habits is a potential colon cancer symptom. In most cases, persons who are diagnosed with advanced colon cancer typically experience a bout of constipation or diarrhea. Bowel symptoms are most likely if the tumor is located closer to the anus. Patients also encounter rectal tenesmus, or a feeling of incomplete defecation, and reduction in diameter of stool.
Abdominal Pain
High-risk symptoms of colon cancer do not show up until late in the course of cancer. Sometimes, the primary tumor ruptures the inside colon wall, creating a hole or perforation. A tear in the lining of the colon allows bowel contents to seep into the abdominal cavity, causing acute abdominal pain. It also puts patients at risk for infections.
