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Anal Cancer

Clinical OncologyGeneral Surgery

Anal cancer is a relatively rare form of cancer, and the types of tumours in the anus are more complex due to their location at the junction of the inner and outer layers of the embryonic tissues. Anal cancer typically originates from the tissues around the anus, including the anal skin, anal canal, or the mucous membrane inside the anus.

Symptoms

The symptoms of anal cancer are similar to those of haemorrhoids, making them easy to overlook. The following are signs of anal cancer:

Rectal bleeding
Itching in or around the rectum
Lump or mass near the anal opening
Pain or a feeling of fullness in the anal area
Narrowing of stools or other changes in bowel habits
Abnormal discharge from the anus
Fecal incontinence (loss of bowel control)
Enlarged lymph nodes in the anal or groin area

The exact cause of anal cancer is still unknown, but certain factors increase the risk of developing cancer:

HPV Infection	Human Papillomavirus (HPV) is a sexually transmitted virus, and individuals with a history of anal intercourse or multiple sexual partners are at an increased risk of contracting HPV.
Weakened Immune System	When the body's immune system is weakened, viruses like HPV become more active. Common factors include HIV infection, use of immunosuppressive drugs, or organ transplant recipients.
Smoking	Smoking reduces the effectiveness of the immune system in resisting HPV infection. Several studies have indicated that smokers have an increased incidence of anal cancer.

Many cases of anal cancer can be detected early because early-stage symptoms are noticeable, such as the mentioned rectal bleeding. Unfortunately, some anal cancers may only cause symptoms in advanced stages, potentially delaying diagnosis. When a doctor suspects a patient may have anal cancer, the following examinations are conducted for a more accurate assessment:

Digital Rectal Exam

The doctor, wearing gloves and lubricating a finger, inserts it into the patient's anus and rectum to check for any hard lumps or tumours. This is the initial examination, and further investigations are carried out if abnormalities are detected.

Anoscopy

The doctor applies gel to an anoscope, gently inserts it into the anus, and lowers it into the rectum. By illuminating the tube, the doctor can observe the lower rectum and anus and obtain biopsy samples from abnormal areas simultaneously.

Colonoscopy

The doctor, using a colonoscope, can visualize the anus, rectum, and the entire colon. It allows the doctor to take tissue samples from the inner part of the anus.

Biopsy

If abnormal tissue growth is observed during a colonoscopy, the doctor will take a portion to check for cancer. If the change is in the anal canal and the tumour is small, the doctor may attempt to remove the entire tumour during the biopsy.

Blood Tests

HIV Test: Since individuals with HIV are at a higher risk of HPV infection, which increases the risk of anal cancer, doctors may conduct an HIV test to check for a connection.

Pap Smear

This test can detect abnormal changes in cervical cells. While cervical Pap smears are primarily for early detection of cervical cancer in women, they can also be applicable in high-risk populations (such as HIV-positive individuals or those with human papillomavirus infection), with an accuracy rate of around 70%.

Digital Rectal Exam (DRE)	The doctor, using a colonoscope, can visualize the anus, rectum, and the entire colon. It allows the doctor to take tissue samples from the inner part of the anus.
Anoscopy	The doctor applies gel to an anoscope, gently inserts it into the anus, and lowers it into the rectum. By illuminating the tube, the doctor can observe the lower rectum and anus and obtain biopsy samples from abnormal areas simultaneously.
Colonoscopy	The doctor, using a colonoscope, can visualize the anus, rectum, and the entire colon. It allows the doctor to take tissue samples from the inner part of the anus.
Biopsy	If abnormal tissue growth is observed during a colonoscopy, the doctor will take a portion to check for cancer. If the change is in the anal canal and the tumour is small, the doctor may attempt to remove the entire tumour during the biopsy.
Blood Tests	HIV Test: Since individuals with HIV are at a higher risk of HPV infection, which increases the risk of anal cancer, doctors may conduct an HIV test to check for a connection.

According to the American Cancer Society, anal cancer can be categorized into the following types:

Squamous Cell Carcinoma — Arises from the squamous cells lining most of the anal canal and the anal margin.
Basal Cell Carcinoma — A type of skin cancer that can develop in the skin around the anus.
Melanoma — Originates from cells in the skin or the inner lining of the anus.
Adenocarcinoma — Originates from cells near the rectum in the upper part of the anus, glands beneath the anal mucosa, or apocrine glands (a type of sweat gland in the skin around the anus).

While anal cancer is relatively rare, there has been an increasing trend in recent years. Anal cancer is uncommon in individuals under 35, and the likelihood of developing it increases with age, with an average age of diagnosis around 60 years old.

Staging

Factors determining the staging of anal cancer include the tumour's size, whether it has spread, and if it has invaded more distant body tissues. The specific stages are as follows:

Stage 0	Precancerous cells are only in the mucosa (a layer of cells inside the anus), without spreading to nearby lymph nodes or distant locations.
Stage I	The tumour diameter is no more than 2 cm, and cancer cells have not spread to nearby lymph nodes or distant locations.
Stage IIA	Tumour diameter is over 2 cm but not more than 5 cm, with no spread to nearby lymph nodes or distant locations.
Stage IIB	The tumour diameter is over 5 cm with no spread to nearby lymph nodes or distant locations.
Stage IIIA	The tumour diameter is no more than 2 cm, and cancer cells have spread to nearby lymph nodes but not distant locations. Tumour diameter is over 2 cm but not more than 5 cm, with cancer cells spreading to nearby lymph nodes but not to faraway places.
Stage IIB	Tumor of any size growing into nearby organs such as the vagina, urethra, prostate, or bladder. Cancer cells have not spread to nearby lymph nodes or distant locations.
Stage IIIC	The tumour diameter is over 5 cm, with cancer cells spreading to nearby lymph nodes but not to distant locations.
Stage IV	Tumors of any size, possibly growing into nearby organs. Cancer cells may or may not have spread to nearby lymph nodes but have spread to distant organs like the liver or lungs.

Doctors will determine the treatment plan based on the location, type, and stage of the patient's tumour, considering the patient's age and overall health. The fundamental goal of treatment is to preserve the muscles of the anal sphincter, allowing the patient to control bowel movements and maintain overall quality of life.

Radiation Therapy	High-energy rays are directed at the tumour outside the body to kill cancer cells. Newer technologies provide higher radiation doses while minimizing damage to nearby healthy tissues.
Chemotherapy	The use of drugs or radiation sensitizers can eliminate rapidly dividing cancer cells, enhancing the ability of radiation therapy to kill cancer cells.
Immunotherapy	Drug use stimulates the patient's immune system, enabling the body's immune mechanisms to attack cancer cells, potentially shrinking tumours or slowing their growth.
Surgical Treatment	In most cases, surgery is not the primary treatment for anal cancer. If surgery is necessary, the type of surgery depends on the type and location of the tumour. Local Excision A surgery that removes only the tumour and a small amount of surrounding normal tissue. Local excision is performed if the tumour is small and has not spread to nearby tissues or lymph nodes. In most cases, this procedure can preserve the sphincter muscles and maintain normal bowel function. Abdominoperineal Resection (APR) APR is a standard treatment for anal cancer. The surgeon makes an incision in the abdomen and another around the anus to remove the anus, rectum, and a portion of the sigmoid colon. Some nearby lymph nodes in the groin area are also removed. Due to the removal of the anus and anal sphincter muscles, a new opening is created for bowel movements. However, APR is now used less frequently, and alternatives like radiation therapy and chemotherapy are considered first. APR is typically reserved for cases where other treatments are ineffective or in the event of cancer recurrence.