Amelanotic malignant melanoma rarely occurs in the oral cavity. We encountered and treated patient with a nodular amelanotic malignant melanoma arising in the maxilla. An 84-year-old woman was referred to our hospital because of a painless, pedunculated, nonpigmented tumor in the center of the anterior alveolar region of the maxilla. The clinical diagnosis was a benign tumor, and the lesion was excised. However, the histopathological diagnosis was malignant fibrous histiocytoma.
Three months later, a small, partially pigmented tumorous lesion appeared in the same region. The tumor was resected, and minute quantities of melanin granules were observed in some tumor cells histologically. The specimen was diagnosed as amelanotic malignant melanoma. We performed immunohistochemical studies, and positive immunoreactivity for HMB-45 was found in each specimen, confirming the diagnosis.
Although the patient subsequently underwent rotation radiotherapy to the maxilla, recurrence was found in the nasal cavity and ethmoidal sinuses 13 months after radiation therapy. The tumor grew rapidly, and the patient died 2 years 5 months after presentation.