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WHO Classification of Tumours
Melanoma, NOS
Anus and anal canal


Definition

A malignant, usually aggressive tumor composed of atypical, neoplastic melanocytes. Cutaneous melanomas may arise from acquired or congenital melanocytic or dysplastic nevi. Melanomas frequently metastasize to lymph nodes, liver, lungs, and brain.

Anal melanoma is rare, representing 13% of all anal tumours. Patients most commonly present in the fifth or sixth decades of life with pain, rectal bleeding or a mass. The histological features are similar to those of cutaneous melanomas that express S100 protein. Most cases show a junctional component adjacent to the invasive tumour, and this finding is evidence that the lesion is primary rather than metastatic. Metastases are frequent at time of presentation, and the prognosis is poor; 5-year survival is < 20%

Click to access Pubmed
Stoidis CN, Spyropoulos BG, Misiakos EP, Fountzilas CK, Paraskeva PP, Fotiadis CI (2009)
Diffuse anorectal melanoma; review of the current diagnostic and treatment aspects based on a case report.
World J Surg Oncol 7: 64



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Topographic definition of the anal canal, anal margin and perianal region