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Learn About Colon Cancer©
Written by Cancer Center Staff

Source: Cancer Resource Room

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What is Colon Cancer?
Any cancer that starts in the colon (large intestine) is called colon cancer. Cancers are formed by abnormal cells that grow and divide without control. These cancer cells replace normal cells and form a tumor or lump. As a tumor gets bigger, it can grow into nearby tissues and organs. Cancer cells can spread to other parts of the body through the blood or lymph vessels. Most colon cancers start in the cells that line the inside of the large intestine. Tumor cells grow there, invade through the layers of the colon, and spread to lymph nodes and other tissues. Colon cancer is one of the most common cancers in the US, with about 130,000 new cases a year.

Large Intestine. Massachusetts General Hospital Cancer Center, Cancer Resource Room, Boston, MAWhat is the colon and what does it do?
The large intestine (colon) is the last part of the digestive system before wastes leave the body.

The colon is divided into five parts:

  1. cecum - part closest to the small intestine
  2. right colon
  3. transverse colon – part that connects the right and left
  4. colon
  5. left colon
  6. sigmoid colon - part just above the rectum

The large intestine is separated from the small intestine by a circle of muscle called the ileocecal valve. It controls the flow of fluid from the small to the large bowel. The large intestine absorbs water and some nutrients, and eliminates wastes from our diets.

There are five layers of tissue that make up the colon:

  1. lining layer (lamina propria)
  2. muscular layer for the lining (muscularis mucosa)
  3. support tissue for lining layers (submucosa)
  4. muscle (muscularis)
  5. outside covering layer (serosa)

Colon cancer usually starts in the lining layer. It grows larger and deeper through the other layers, spreading to nearby tissues and lymph nodes. The tumor can make a hole in the colon into the abdomen or into another organ. The intestines can keep working even though a cancer has started in one part of it. This means a colon cancer can get quite large or deep before it is diagnosed.

What are the symptoms of colon cancer?
Symptoms caused by colon cancer are from the tumor taking up space inside the intestine, from the loss of small amounts of blood from the tumor into the bowel, and from the tumor growing through the intestine into the abdomen or other organs. A tumor can cause a blockage or obstruction so the stool cannot pass by easily. The cancer tissue can bleed into the intestine, making the person anemic. Some symptoms are caused by cancer cells invading other tissues or putting pressure on nerves. Colon cancer usually grows for some time before it causes any symptoms. When symptoms occur they include:

  • abdominal pain
  • change in bowel habits
  • weight loss (without dieting)
  • weakness or tiredness (due to anemia—a low blood count)
  • nausea and vomiting
  • swelling of the abdomen
  • rectal bleeding
  • bloody or black, sticky bowel movements
  • rectal pain

These symptoms can have other causes and should be checked by a doctor.

How is colon cancer diagnosed?
A patient’s medical history and physical exam are the first steps in making a diagnosis of any disease. The medical history includes many details of a person’s health. In particular, the history will focus on the digestive tract—changes in eating habits, changes in bowel movements, abdominal pain or bloating, and how food affects any of the symptoms. In the case of colon cancer, the patient’s history may include information about other diseases such as:

  • inflammatory bowel disease
  • granulomatous colitis
  • previous colorectal cancer or polyps
  • radiation of the pelvis
  • GI surgery in the past, including gallbladder removal
  • family history of polyps or colon cancer

The physical exam will focus on areas of discomfort in the abdomen, the presence of a mass (a lump) in the abdomen, an enlarged liver, fluid or swelling in the abdomen, any skin color change (yellow jaundice), or enlarged lymph nodes. The stool must be checked for blood. The rectum and anus need to be checked for lumps by digital (finger) exam.

After the history and physical exam, some diagnostic tests may be ordered. Blood tests and a chest x-ray check a patient’s general health. Some blood tests that may be done include:

  • Blood count- to check for anemia and iron deficiency
  • Liver enzymes- for possible spread to the liver
  • CEA-marker protein that may increase

Special tests that are useful in diagnosing colon cancer are:

  1. CT scan—x-rays made in thin cross-sections of the abdomen. This set of x-rays can show a tumor in the colon, as well as its spread to nearby tissues and lymph nodes. This test is especially useful for finding disease spread to the liver.
  2. Colonoscopy—this test uses a thin, flexible tube with a camera in it to look at the inside of the colon (large intestine) and rectum. The camera images are displayed on a TV monitor allowing the doctor to see the inside of the entire large intestine. The colonoscope is passed through the anus and rectum into the colon and up through the large intestine. A biopsy can be taken of any tissue that looks abnormal. Lumps of tissue inside the colon called polyps can be removed. In preparation for the test, the patient drinks only liquids the day before, including a fluid that helps clean out the bowel. The procedure is done using sedation for relaxation. It is not a painful procedure and does not require anesthesia.

What is a biopsy? What does it mean to a patient?
A biopsy is a small piece of tissue or group of cells used to diagnose a disease. The tissue is taken from a spot suspected of being abnormal. Then the biopsy tissue is looked at under a microscope by a pathologist. The diagnosis is based on the appearance of the tissue and cells. The biopsy result is used to decide the patient’s treatment.

What if the biopsy shows colon cancer?

If the biopsy shows cancer, the next step is to find out how much disease there is. You need to know:

  • how widespread is the disease in the colon
  • how many layers has it spread through
  • has it spread beyond the colon into the lymph nodes, into nearby tissues, or to distant lymph nodes and other organs

What tests are used to find the spread of colon cancer?

  • CT scans—these are X-rays that show cross-section pictures of the body. CT images let the radiologist see the abdominal organs in many ways, going across, as well as up and down, the body. An abdominal CT scan shows the stomach, lymph nodes, liver, gallbladder and bile ducts, pancreas, small and large intestines, kidneys, major blood vessels, and part of the spine. The patient may need to drink a contrast solution to help outline the digestive organs. An IV is used to give the patient contrast “dye” that travels through the blood. Contrast dye in the blood makes a person feel very warm for a brief time, and causes a sensation of needing to pee urgently. Both feelings pass quickly. CT scans are not painful but do require lying on a table for about 30 minutes.
  • Laparoscopy—this procedure lets the surgeon look inside the abdomen with a laparoscope, a thin tube with a small camera in the end. The laparoscope is inserted through a small abdominal incision. It transmits pictures from inside the abdomen to a TV monitor so the surgeon can see what tissues look normal and which do not. This helps plan the patient’s surgery and other treatments. This procedure is used for small intestine disease much more often than for colon cancer. Laparoscopy is done in the operating room with the patient under general anesthesia.

The information about the patient including the medical history, physical exam, blood tests, x-rays, special scans, and procedures are used to describe the patient’s stage of disease and plan the best treatment for that disease.

What is the stage of a cancer? How is it determined?
The stage of a cancer describes how much cancer there is, what tissue it has invaded, and whether or not it spread to lymph nodes and other parts of the body. The higher the stage, the more complicated the disease. The stage is a combination of the size of tumor growth, the number of lymph nodes involved, and the spread to other sites (metastases). For colon cancer, there are at least two systems for deciding the stage of the disease. One was developed by a surgeon named Dukes. It is based on the growth of tumor through the layers of the colon, invasion of nearby tissues, and spread to lymph nodes. The staging system used most today is the Tumor, Nodes, Metastasis system.

These are the TNM stages for adenocarcinoma of the colon:

  • Stage 0: cancer cells are only in the lamina propria (lining layer), and have not invaded the outer layers or lymph nodes. May be called, “carcinoma in situ.”
  • Stage I: cancer has invaded from the lining layer into the submucosa or as far as the muscle layer. Cancer has not grown into any lymph nodes.
  • Stage II: cancer has invaded the muscle layer, serosa, and into nearby tissue, but has not spread to lymph nodes.
  • Stage III: cancer has grown through all layers of the intestine, into nearby tissues, and to a few nearby (regional) lymph nodes. No tumor has traveled to distant nodes or organs.
  • Stage IV: cancer has spread to other parts of the body (liver, lungs, bones, brain), with or without lymph node spread.

Support & Education Programs

We know that being diagnosed with cancer can be stressful for you and your family. We offer a variety of cancer support services to help patients and families gain the support and information they will need to meet the challenges ahead.

To find the Colon Cancer Support Group, other education workshops, and wellness services offered this month, please view the HOPES calendar.

Read the most recent SUPPORT publication, a resource written by patients and families for patients and families >>>