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.

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