Anorectal malignant amelanotic melanoma: Report of a rare aggressive primary tumor.

Malignant melanoma of the anorectal region is a very rare aggressive malignant neoplasm and it constitutes 1% of all malignant lesions of this area. About 70% of these lesions are pigmented, whereas 30% are amelanotic. Demonstration of immune markers of melanoma by immunohistochemistry (IHC) is required for confirming the diagnosis of amelanotic malignant melanoma.