What is Anal Cancer?

The anus, about 1-1/2 inches long, connects the rectum (lower part of the large intestine) to the outside of the body, allowing solid waste (stool) to pass out. The sphincter muscles open and close the anus to control waste flow. The anus is lined with squamous cells, also found in the bladder, cervix, vagina, urethra, and other areas.

Types of Anal Cancer

Several types of tumors may develop in the anus. Some are malignant (cancer), others benign or precancerous. Main types include:

• Carcinoma in situ: Early cancer or precancerous cells on surface cells of the anal canal, also called Bowen’s disease.
• Squamous cell cancer: Forms in the cells lining the anus; most common anal cancer type.
• Adenocarcinomas: Develop in glands around the anus.
• Skin cancers: Basal cell and melanoma, often found in advanced stages.

Risk Factors

Anything increasing your chance of anal cancer is a risk factor, including:

• Age: Most cases found in people older than 50
• Human papillomavirus (HPV) infection
• Human immunodeficiency virus (HIV) or AIDS
• Multiple sexual partners
• Anal intercourse
• Frequent anal redness, swelling, soreness
• Tobacco use
• Immunosuppression (e.g., immune-suppressing drugs after organ transplant)

Not everyone with risk factors develops anal cancer, but discuss your risks with your doctor.

Symptoms

Anal cancer often shows no symptoms. If present, symptoms may include:

• Anal or rectal bleeding
• Pain or pressure around the anus
• Change in bowel habits
• Narrower stool than usual
• Lump near the anus
• Swollen lymph nodes in anal or groin area
• Anal discharge

These symptoms don’t always mean cancer but see your doctor if they last more than two weeks.

Diagnosis

Tests used to diagnose anal cancer and check spread include:

• Digital rectal exam: Doctor feels for lumps using a gloved finger.
• Imaging tests:
  • Anoscopy: Camera tube into anus to examine and biopsy.
  • Proctoscopy: Camera tube from anus to rectum to examine and biopsy.
  • Colonoscopy and virtual colonoscopy (CT colonoscopy)
  • CT scans, MRI scans, PET/CT scans
  • Endo-anal or endorectal ultrasound (sonogram with an endoscope)
  • Chest X-ray
• Fine-needle aspiration biopsy: Sampling lymph node cells to check spread, guiding treatment decisions.