Anal cancer

Anal cancer is a rare tumor. Risk factors include infection with human papillomavirus (HPV), immunodeficiency, and receptive anal intercourse. The most common clinical features are rectal bleeding (up to 45% of cases), pruritus ani, and tenderness or pain in the anal area. Anal cancer presents mainly as squamous cell carcinoma and in rare cases as adenocarcinoma or other non-epidermoid cancers. Depending on the exact localization and stage, it requires excision and/or radiochemotherapy. If the condition is treated in its early stages, the prognosis is favorable.

• Incidence: ∼ 8,000 cases diagnosed per year in the US ^[1]
• More common in HIV-positive individuals and men who have sex with men

Epidemiological data refers to the US, unless otherwise specified.

• Risk factors
  • Immunodeficiency (e.g., HIV)
  • Receptive anal intercourse
  • Smoking
  • HPV infection (esp. types 16 and 18)

• Rectal bleeding (most important initial symptom)
• A lump or tumor around the anus
• Pruritus ani
• Tenderness, pain in the anal area
• Fecal incontinence
• History of anorectal condyloma

• Physical examination
  • Inspection
  • Digital rectal exam
• Invasive procedures
  • Anoscopy
  • Biopsy for histology (small tumors are fully excised)
• Staging ^[2]
  • Endosonography, abdominal CT, pelvic MRI, chest x-ray/CT, PET scan
  • Women with anal cancer should also undergo a gynecologic examination for screening for cervical cancer.

• Histology: primarily squamous cell carcinoma; rarely adenocarcinoma or other non-epidermoid cancers
• Location
  • Above the anal verge: anal canal tumors
  • Below the anal verge: anal margin tumors

• Anal canal cancer ^[3]
  • Treatment of choice: radiochemotherapy
  • Recurrent cancers are treated surgically.
• Anal margin cancer
  • If possible, local excision with safety margin
  • Advanced tumor
    • (Neoadjuvant) radiochemotherapy
    • Subsequent resection depending on the size of the tumor
    • In some cases, remission may be achieved with radiochemotherapy alone.

• Metastasis
  • Local invasion of adjacent organs
  • Lymphatic spread (30% of patients): perirectal, paravertebral, inguinal, femoral
  • Hematogenous spread (< 10% of patients): liver, bone, lung ^[4]

We list the most important complications. The selection is not exhaustive.

• Anal cancer of the dentate line: The 5-year survival rate after radiochemotherapy is > 80%.
• Anal cancer of the anal verge: The prognosis is favorable if complete local excision is possible. The 5-year survival rate after rectal amputation is approx. 50%.

References:^[5]