Anal Cancer

Diagnosis

The diagnosis of anal cancer is made through the following techniques:

• Medical history and physical examination: Cancer specialists comprehensively evaluate the risk factors for anal cancer in patients by obtaining information related to family history, medical history, and history of smoking, any cancer, sexually transmitted disease, or infection, primarily due to human papillomavirus. The patients are checked for signs of anal cancer during physical examination. The patients undergo a digital rectal examination to detect an abnormal mass or lump in the anal canal.
• Blood tests: Individuals are also advised to undergo blood tests to check if the risk factors for HIV infection are present.
• Ultrasound: Endoanal ultrasound is the preferred ultrasound technique to determine the presence of anal cancer or to measure the response to anal cancer treatment. The transducer is inserted into the anal canal to obtain clear internal images during the test. Endoanal ultrasound assists in determining the depth of invasion of cancer into the layers of the anal canal and anal sphincter.
• Magnetic Resonance Imaging (MRI): This technique is preferred for staging anal cancer. The staging of the squamocellular anal carcinoma performed through MRI is based on the maximum tumor diameter and invasion of cancer into lymph nodes and adjacent organs. The advantages of MRI for anal cancer include biological non-invasiveness, excellent tissue differentiation, and the safety of gadolinium-based contrast agents. Magnetic resonance imaging also helps identify the metastasis of anal cancer to the brain, liver, or spinal cord.
• Computed Tomography: Computed tomography is used to obtain detailed images of the anal canal. The technique also provides information about the metastasis of anal cancer to nearby lymph nodes or other organs, such as the liver or lungs. Computed tomography in anal cancer assists cancer specialists in conducting needle biopsies with accuracy and precision.
• Positron Emission Tomography (PET) scan: Positron emission tomography for anal cancer not only helps in diagnosing and staging but also measures the response to anal cancer treatment. There has been increasing use of PET scans in diagnosing and staging anal cancer as most anal cancers respond to fludeoxyglucose, a radioactive tracer used in the PET scan.
• Colonoscopy: This procedure is performed through a colonoscope, a thin, long, and flexible tube with a video camera at the end. It provides images of the anus, rectum, and colon. If any abnormal tissue is viewed on the monitor, the technique also allows for obtaining the tissue sample for further investigation. The patient may also undergo flexible sigmoidoscopy, but the images obtained are only from the anus, rectum, and lower colon. The procedure is performed under sedation.
• Anoscopy: This method is performed through an anoscope, a hollow, small, and firm tube with a light at the end. The anoscope is coated with a gel and inserted into the anus. The light at the end of the anoscope allows the cancer specialist to visualize the internal lining of the anus and lower rectum. The samples of the abnormal tissues may also be obtained during the procedure for further analysis.
• Chest x-ray: The patients may also have to undergo a chest x-ray to detect if cancer has spread to the lungs. However, the test is not generally used if the patient has already undergone a chest CT scan.
• Biopsy: The samples of the abnormal tissues are obtained and sent to the laboratory for confirmatory diagnosis of cancer during a biopsy. If the abnormal tissue is very small, the cancer specialist removes it completely during the biopsy. A biopsy also helps determine the spread of cancer in the lymph nodes. The samples of the lymph nodes are obtained through fine needle aspiration.