• Clinical science

Anal cancer

Summary

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.

Epidemiology

  • Incidence: ∼ 8000 cases diagnosed per year in the U.S.
  • More common in HIV-positive individuals and men who have sex with men

References:[1][2]

Epidemiological data refers to the US, unless otherwise specified.

Etiology

References:[2]

Classification

TNM Classification for Anal Cancer

TNM Dimension
T1
  • Tumor 2 cm or less in greatest dimension
T2
  • Tumor more than 2 cm but not more than 5 cm in greatest dimension
T3
  • Tumor more than 5 cm in greatest dimension
T4
N1
N2
N3
M1

UICC (Union for International Cancer Control) staging of anal carcinoma

UICC stages

TNM stages

Stage I T1, N0
Stage II T2 or T3, N0
Stage IIIA T3, N1 or T4, N0
Stage IIIB any T, N2 or N3 or T4, N1
Stage IV M1

Clinical features

  • 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

References:[2]

Diagnostics

  • Physical examination
  • Invasive procedures
    • Anoscopy
    • Biopsy for histology (small tumors are fully excised)
  • Staging: endosonography, abdominal ultrasound, abdominal CT, pelvic MRI, chest x-ray/CT

References:[2]

Pathology

  • 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

References:[2][3]

Treatment

  • Anal canal cancer
    • 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 (abdominoperineal rectal amputation may be required)
      • In some cases, remission may be achieved with radiochemotherapy alone.

References:[2]

Complications

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

References:[4]

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

Prognosis

  • Anal cancer of the dentate line: The 5-year survival rate after radiochemotherapy is approx. 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:[2]