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Annals of Ibadan Postgraduate Medicine

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Oral Amelanotic Melanoma

AO Adisa, WO Olawole, OF Sigbeku

Abstract


Malignant melanomas of the mucosal regions of the head and neck are extremely rare neoplasms accounting for less than 1% of all melanomas.
Approximately half of all head and neck melanomas occur in the oral cavity. Less than 2% of all melanomas lack pigmentation, in the oral
mucosa however, up to 75% of cases are amelanotic. No etiologic factors or risk factors have been recognized for oral melanomas. Some authors have suggested that oral habits and selfmedication may be of etiological significance. Oral melanoma is rare but it is relatively frequent in countries like Japan, Uganda, and India. It is rarely identified under the age of 20 years. In Australia where cutaneous melanomas are relatively common primary melanoma of the oral mucosa is rare.
The surface architecture of oral melanomas ranges from macular to ulcerated and nodular. The lesion is said to be asymptomatic in the early
stages but may become ulcerated and painful in advanced lesions. The diagnosis of amelanotic melanoma is more difficult than that of pigmented lesions. The neoplasm consists of spindle-shaped cells with many mitotic figures and no cytoplasmic melanin pigmentation. Immunohistochemistry using S-100, HMB-45, Melan-A and MART-1 will help in establishing the correct diagnosis.
Radical surgery with ample margins and adjuvant chemotherapy are appropriate management protocol for malignant melanoma. Oral melanoma is associated with poor prognosis but its amelanotic variant has even worse prognosis because it exhibits a more aggressive biology and because of difficulty in diagnosis which leads to delayed treatment.

Keywords: amelanotic melanoma, oral cavity




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