How Is Anal Cancer Diagnosed
Anal cancer is relatively easy to diagnose because it is located in a very accessible site. Although some cases of anal cancer in people at high risk for that disease are diagnosed by screening tests, such as the digital rectal exam and/or anal cytology testing, as mentioned above, most people are diagnosed after their cancer starts to cause symptoms.
Signs and Symptoms of Anal Cancer
Some cases of anal cancer cause no symptoms at all. Bleeding occurs in more than half of patients and is usually the first sign of the disease. Often the bleeding is minor. At first, most people assume that hemorrhoids are the cause of their bleeding.
Other important symptoms of anal cancer include:
- pain in the anal area
- change in the diameter of stool
- abnormal discharge from the anus
- swollen lymph nodes in the anal or groin areas
There are a number of benign conditions, such as hemorrhoids, fissures, or anal warts, that can produce similar symptoms. In about 65% of anal cancers, benign anal conditions are present also. But if you have any of these signs or symptoms listed above, please discuss them with your doctor without delay. Remember, the sooner you receive a correct diagnosis, the sooner you can start treatment and the more effective your treatment will be.
Procedures Used to Diagnose Anal Cancer
Sometimes your doctor will detect anal cancer during a routine physical exam or during a minor procedure, such as removing a hemorrhoid. Treatment of cancers found in this way is often very effective because the tumors are found early in the course of the disease.
The digital rectal exam often reveals the presence of an unusual growth. However, since doctors cannot see what they feel, other steps are needed if you have symptoms or if your doctor suspects you have anal cancer.
Among the procedures used in diagnosing anal cancer are:
- anoscopy - use of a special device to view the anus
- proctoscopy - use of a lighted scope to view inside the anal canal
- transrectal ultrasound - use of a device that is inserted into the rectum and produces sound waves; echoes of these sound waves are detected and analyzed by a computer to create an image of the anus and nearby tissues
Your doctor also may ask you to have an exam using a sigmoidoscope or a colonoscope. These instruments allow the doctor to see inside the colon and look for abnormal growths, bleeding, or other signs of disease higher up.
If a suspicious growth is found, your doctor will want to do a biopsy. In this procedure, a small piece of the tissue is cut out and sent to a laboratory. A pathologist (a doctor specializing in laboratory diagnosis of diseases) will look at the tissue under a microscope. If cancer is present, the pathologist sends back a report describing the cell type and extent of the cancer. Usually, a biopsy causes only slight discomfort and you will not have to stay in the hospital. However, if you have pain or muscle spasms during the exam, an anesthetic can be given.
If the tumor is very small and has not grown below the surface of the anus into other tissues, your doctor may attempt to remove the entire tumor during the biopsy.
There is a risk that anal cancers, like other forms of cancer, can spread through the lymphatic system. Lymph nodes are bean-sized collections of immune system cells. Swollen lymph nodes in the groin are sometimes a sign of spreading anal cancer. These can also be a reaction to infections. To distinguish between these two causes, your doctor may use a thin needle to withdraw a small sample of fluid and tissue fragments from the lymph node. The lab will study this fluid to look for the presence of cancerous cells. This procedure is called a fine needle aspiration biopsy. In some cases, an operation to remove the lymph nodes may be done.
Sentinel node biopsy: Recently, a new way of examining local lymph nodes has been developed. In this method a radioactive tracer material is injected around the tumor. Then the groin lymph nodes are scanned to spot the radioactivity. The surgeon will then make a small incision over the radioactive area to remove the underlying lymph nodes. Often a blue dye will be injected into the tumor at the same time as the radioactive material. Then the surgeon will remove any blue-stained lymph nodes. Studies of other cancers have shown that if there has been spread of cancer to lymph nodes, the cancer has gone to the node that has picked up the blue dye or radioactivity.
Imaging Studies
If cancer is found, you will need to have certain tests to determine the stage (extent) of the disease.
Ultrasound: A transrectal ultrasound can show how far the cancer has invaded nearby tissues. Ultrasound uses sound waves and their echoes to produce a picture of internal organs or masses. A small microphone-like instrument called a transducer emits sound waves. These high-frequency sound waves are transmitted into the area of the body being studied and echoed back. The sound wave echoes are picked up by the transducer and converted by a computer into an image that is displayed on a computer screen.
Normally, ultrasound is a very easy procedure. It uses no radiation, which is why it is frequently used to look at developing fetuses. With endorectal ultrasound, the transducer is inserted directly into the rectum, which can be uncomfortable.
Computed tomography (CT): The CT scan is an x-ray procedure that produces detailed cross-sectional images of your body. Instead of taking one picture, as does a conventional x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these pictures into an image of a slice of your body. The machine will take pictures of multiple slices of the part of your body that is being studied. This test can help tell if your anal cancer has spread into your liver or other organs. Often after the first set of pictures is taken you will receive an intravenous injection of a “dye” or radiocontrast agent that helps better outline structures in your body. A second set of pictures is then taken.
CT scans can also be used to precisely guide a biopsy needle into a suspected metastasis. For this procedure, called a CT-guided needle biopsy, the patient remains on the CT scanning table, while a radiologist advances a biopsy needle toward the location of the mass. CT scans are repeated until the doctors are confident that the needle is within the mass. A fine needle biopsy sample (tiny fragment of tissue) or a core needle biopsy sample (a thin cylinder of tissue about ?? inch long and less than 1/8 inch in diameter) is removed and examined under a microscope.
CT scans are more tedious than regular x-rays because they take longer and you usually need to lie still on a table for 15 to 30 minutes while they are being done. But just like other computerized devices, they are getting faster and your stay might be pleasantly short. You might feel a bit confined by the equipment while the pictures are being taken.
You will need an intravenous line through which the contrast “dye” is injected. The injection can cause some flushing. Some people are allergic and get hives or rarely more serious reactions like trouble breathing and low blood pressure. Be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays. You may be asked to drink 1 to 2 pints of a contrast solution. This helps outline the intestine so that it is not mistaken for tumors.
Magnetic resonance imaging (MRI): MRI scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. Like a CT scanner, this produces cross-sectional slices of the body. An MRI can produce slices that are parallel with the length of your body. Like a CT scan, a contrast material might be used, but not as often.
MRI scans are also very helpful in looking at the brain and spinal cord. MRI scans are a little more uncomfortable than CT scans. First, they take longer ??? often up to an hour. You have to be placed inside tube-like equipment, which is confining and can upset people with claustrophobia ( a fear of enclosed spaces). The machine makes a thumping noise that you may find disturbing. Some places will provide headphones with music to block this out.
Chest x-ray: This test may be done to determine whether anal cancer has spread to the lungs.
Positron emission tomography: Positron emission tomography (PET) uses glucose (a form of sugar) that contains a radioactive atom. Cancer cells in the body absorb large amounts of the radioactive sugar and a special camera can detect the radioactivity. PET is useful when your doctor thinks the cancer has spread, but doesn’t know where. PET scans can be used instead of several different x-rays because it scans your whole body.