Melanoma of the Anal Canal

Melanoma of the anal canal:
- Is rare:
  - Of all melanomas diagnosed:
    - Only 0.4% to 1.6% arise in the anal canal
Lesions tend to be diagnosed at an advanced stage:
- With the onset of symptoms such as pruritus and bleeding
Often, these tumors are diagnosed in a delayed fashion:
- Because of confusion with more common lesions of the anal canal:
  - Such as hemorrhoids
Once a biopsy specimen was evaluated, the histology and immunohistochemistry was diagnostic of an anal melanoma:
- A staging work-up in the form of cross-sectional imaging:
  - Is the standard of care for determining whether distant or regional disease may be present
- If staging studies are negative for metastatic disease:
  - Then the next step is to control the primary lesion:
    - There are two reasonable options for controlling the primary lesion in the setting of anal canal melanoma:
      - Abdominoperineal resection or local excision
    - Both are accepted practices; however, over the past several decades, there has been a trend toward less aggressive surgery:
      - In the form of local excision
    - The findings of retrospective studies support a less aggressive approach:
      - Because of a lack of difference in overall or disease-free survival between groups treated with either radical surgery or local excision:
        
        Ross et al reported on 26 patients with anal melanoma treated with either radical surgery (abdominoperineal resection) or local excision and found no difference in overall and recurrence-free survival between the two groups
References:
- Iversen K, Robins RE. Mucosal malignant melanomas. Am J Surg. 1980;139:660-664.
- Nigro ND, Vaitkevicius VK, Considine B Jr. Combined therapy for cancer of the anal canal: a preliminary report. Dis Colon Rectum. 1974;17:354-356.
- Ross M, Pezzi C, Pezzi T, Meurer D, Hickey R, Balch C. Patterns of failure in anorectal melanoma: a guide to surgical therapy. Arch Surg. 1990;125:313-316.