Source: Cancer Resource Room
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.
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
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
- 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
- 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
- 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
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
- 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.
- 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.
- 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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