Most colorectal cancers start as a growth on the inner lining of the colon or rectum. These growths are called polyps. Some types of polyps can change into cancer over time (usually many years), but not all polyps become cancer. The chance of a polyp turning into cancer depends on the type of polyp it is.
Nearly all cases of colorectal cancer develop from polyps. They start in the inner lining of the colon and most often affect the left side of the colon and rectum.
Almost all colon cancers start in the lining of the colon and rectum. When doctors talk about colorectal cancer, this is usually what they are talking about. There is no single cause of colon cancer. Nearly all colon cancers begin as noncancerous (benign) polyps, which slowly develop into cancer.
Signs and symptoms of colon cancer include: A persistent change in your bowel habits, including diarrhea or constipation or a change in the consistency of your stool. Rectal bleeding or blood in your stool. Persistent abdominal discomfort, such as cramps, gas or pain.
The 3 main symptoms of bowel cancer are blood in the stools (faeces), changes in bowel habit – such as more frequent, looser stools – and abdominal (tummy) pain. However, these symptoms are very common and most people with them do not have bowel cancer.
Colon cancer is considered a silent disease. Most of the time there are no symptoms. The symptoms that people may experience include a change in bowel habits, abdominal pain, blood in the stool, and weight loss. If individuals have these symptoms, the disease may already have advanced.
Abdominal pain, aches, or cramps may be symptoms of colorectal cancer. If you have any symptoms that worry you, be sure to see your doctor right away.
Colon cancer, or cancer that begins in the lower part of the digestive tract, usually forms from a collection of benign (noncancerous) cells called an adenomatous polyp. Most of these polyps will not become malignant (cancerous), but some can slowly turn into cancer over the course of about 10-15 years.
No blood test can tell you if you have colon cancer. But your doctor may test your blood for clues about your overall health, such as kidney and liver function tests. Your doctor may also test your blood for a chemical sometimes produced by colon cancers (carcinoembryonic antigen, or CEA).
Colorectal cancer symptoms may be minor or non-existent during the early stages of the disease, although there may be some early warning signs. The symptoms of colorectal cancer may not develop until the disease has progressed into stage 2 or beyond.
Screening for colorectal cancer
Colorectal cancer doesn't just appear suddenly. It starts as a small growth on your colon, called a polyp, which rarely causes symptoms. If left alone over many years, polyps can grow into cancer. The only way to know it's there is to look.
Colorectal cancer can occur in young adults and teenagers, but the majority of colorectal cancers occur in people older than 50. For colon cancer, the average age at the time of diagnosis for men is 68 and for women is 72.
Lack of regular physical activity. A diet low in fruit and vegetables. A low-fiber and high-fat diet, or a diet high in processed meats. Overweight and obesity.
Over 90% of people diagnosed with colorectal cancer are over age 50. As we age, we are more likely to grow colon polyps which may undergo gene changes that turn normal tissue into cancer. This is why age is one of the top colon cancer risk factors. The older your age, the higher your risk of colon cancer.
Colonoscopy. In this test, the rectum and entire colon are examined using a colonoscope, a flexible lighted tube with a lens for viewing and a tool for removing tissue.
Usually if a suspected colorectal cancer is found by any screening or diagnostic test, it is biopsied during a colonoscopy. In a biopsy, the doctor removes a small piece of tissue with a special instrument passed through the scope. Less often, part of the colon may need to be surgically removed to make the diagnosis.
Computed tomography (CT) scans can be used in a few ways to help detect colorectal cancer, find signs of cancer in other areas of the body, or determine how well cancer treatment is working.
In most cases, colon and rectal cancers grow slowly over many years.
By the time the cancer has advanced to stage 4 (metastasized), a number of symptoms may occur depending on where in the body the cancer has spread. However, not everyone will experience symptoms – or the same set of symptoms – as every patient's experience is unique.
Nausea and vomiting can occur if a colon or rectal tumor is obstructing the bowel and inhibiting the passage of liquid or solid waste or gas. Bowel blockage can also be accompanied by painful abdominal cramps, bloating and constipation.
Despite these concerns, there may be subtle clues that suggest the onset of a malignancy, including: Narrow "pencil" stools: Caused by the narrowing of the intestinal passage as the tumor starts to grow. Pain with defecation: Also known as dyschezia, a symptom commonly associated with rectal cancer.
intermittent, and occasionally severe, abdominal pain – this is always brought on by eating. unintentional weight loss – with persistent abdominal pain. constant swelling of the tummy – with abdominal pain. being sick – with constant abdominal swelling.
Myth: I don't need a colonoscopy because I'm not having any symptoms. Fact: Many people are diagnosed with colon cancer when they are feeling just fine. People don't think they can have colon cancer if they feel OK, but they most certainly can.
Here's what we know: As often as 40% of the time, a precancerous polyp — frequently a type called an adenoma — is found during a screening colonoscopy. Colon cancer is found during only in about 40 out of 10,000 screening colonoscopies, Dr. Sand said.
Polyps are common in American adults, and while many colon polyps are harmless, over time, some polyps could develop into colon cancer. While the majority of colon cancers start as polyps, only 5-10% of all polyps will become cancerous.