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Learn About Anal Cancer©
Written by Cancer Center Staff

Source: Cancer Resource Room

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What is Anal Cancer?
Any cancer that starts in the anus or the skin around the anus is called anal cancer. This cancer is formed by abnormal cells that grow and divide without stopping. The 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 anal cancers start in the cells that line the inside of the anus. Tumor cells grow there, invade through the layers of the anus, and spread to lymph nodes and other tissues.

Medical Illustration of the rectum.  Massachusetts General Hospital Cancer Center, Boston, MAThe anus is the last part of the digestive system. It helps control the release of feces (stool or poop) during a bowel movement. The anus and rectum join at a set of circular muscles called sphincters. The sphincters control the release of feces. Maintaining normal sphincter control is the greatest challenge in treating anal cancer.

Anal cancer usually starts in the lining layer of the anus. It grows larger and deeper, spreading to nearby tissues and lymph nodes. The anus can keep working normally even though a cancer has started in one part of it. This means an anal cancer can get quite large or deep before it is diagnosed. Anal and rectal cancers are more likely to cause noticeable symptoms than others tumors in the digestive system.

Are all anal cancers the same?
There are only about 3300 new cases of anal cancer diagnosed in the United States each year. Of these, most anal cancers are squamous cell cancers or cloacogenic cancers. The other types of anal cancer are very rare and include: adenocarcinoma of anal ducts, anal Paget’s, anal melanoma, small cell carcinoma, sarcoma (Kaposi’s), and lymphoma.

What are the symptoms of anal cancer?
Symptoms caused by anal cancer are from the tumor taking up space inside the anus, from the tumor bleeding, and from the tumor growing through the anus into nearby tissues. A tumor can cause a blockage or obstruction so the stool cannot pass by easily. This causes pain and a feeling of an incomplete bowel movement. The cancer tissue can bleed as the stool passes over it. The bleeding is seen on the feces or in the toilet. Some symptoms are caused by cancer cells invading into other tissues or putting pressure on nerves. When symptoms occur they include:

  • anal pain, especially after a bowel movement
  • anal itching
  • anal bleeding or discharge
  • change in bowel habits
  • weakness or tiredness (due to anemia—a low blood count)
  • bloody bowel movements
  • buttock or perineal pain
  • a feeling of not being done after bowel movement

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

How is anal 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 anal cancer, the patient’s history may include information about other diseases such as:

  • inflammatory bowel disease or Crohn’s disease
  • perianal fistula
  • perirectal abscess
  • genital warts
  • previous colorectal cancer or polyps
  • radiation of the pelvis
  • sexually transmitted diseases
  • human papillomavirus
  • HIV

The physical exam will focus on areas of discomfort in the anus and buttocks, the presence of a mass (a lump) in the anus, enlarged lymph nodes, any weakness of the anal sphincter, and loss of sensation around the anus. 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 other tests may be ordered. Blood tests and a chest x-ray check a patient’s general health. A blood count is done to check for anemia (low blood count).

Special tests that are useful in diagnosing rectal cancer are:

  1. CT scan—x-rays made in thin cross-sections of the pelvis. This set of x-rays can show a tumor in the rectum or anus, as well as its spread to nearby tissues and lymph nodes. This test is useful for finding disease in the anus and nearby tissues, but not for finding affected lymph nodes.
  2. Anoscopy—this test uses a short, clear, funnel-shaped tube to look at the inside of the anus and lower rectum. A biopsy can be taken of any tissue that looks abnormal. The procedure is done using sedation for relaxation. It can be a painful procedure and may require anesthesia.
  3. Endorectal ultrasound—a small probe is placed in the anus and rectum and sound waves are sent out. As the sound waves pass through the tissues, a sensor on the lower abdomen picks up the signals and translates them into a picture. A radiologist studies the patterns to see the presence of a tumor, how far it has invaded the surrounding tissue. and whether or not there are enlarged lymph nodes nearby. The test is done in a radiology room. It is only a little uncomfortable, and does not require any medication.

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 helps in planning a patient’s treatment.

What if the biopsy shows anal 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 anus
  • how many tissues has it spread through
  • has it spread beyond the anus into the lymph nodes, into nearby tissues, or to distant lymph nodes and other organs

What tests are used to find the spread of anal 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 slices, 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. A pelvic CT scan shows the lower organs like the bladder, uterus, vagina, prostate gland, rectum and anus. 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 feeling 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.

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 widespread the disease. The stage is a combination of the size of the tumor or extent of tumor growth, the number of lymph nodes involved, and the spread to other sites (metastases). This staging system is called the Tumor, Nodes, Metastasis system. The tumor is measured by its largest dimension. Nodes are described as nearby or regional, or by the number of groups of lymph nodes containing cancer cells. Metastasis is the spread of cancer to other parts of the body.

These are the TNM stages for anal cancer:

  • Stage 0: cancer cells are only in one layer of cells and have not invaded the deeper layers or lymph nodes. May be called, “carcinoma in situ.”
  • Stage I: tumor is 2 cm or smaller. Cancer has not grown into any lymph nodes.
  • Stage II: tumor is more than 2 cm but not larger than 5 cm, and cancer has spread to nearby lymph nodes. Or the tumor is 5 cm or larger, but no cancer is in the lymph nodes.
  • Stage IIIA: tumor of any size, and cancer has spread to one or more nearby (regional) lymph node groups. No tumor has traveled to distant nodes or organs.
  • Stage IIIB: tumor of any size that has invaded neighboring organs (bladder, rectum, vagina, urethra, prostate), and any amount of spread to nearby lymph nodes.
  • Stage IV: tumor of any size. Cancer has spread to other parts of the body (liver, lungs, bones, brain), with or without lymph node spread.

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