• Clinical science

Anal cancer

Abstract

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
  • Tumor of any size invades adjacent organ(s) (e.g., vagina, urethra, bladder); direct invasion of the rectal wall, perirectal skin, subcutaneous tissue, or the sphincter muscle(s) is not classified as 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]