ORAL MELANOMA: A FATAL ENTITY

INTRODUCTION: Oral melanomas are uncommon and similar to their cutaneous counterparts, are neoplasm that developed from melanocytic cells lying in the basal layer of the mucosa, its incidence is about 1.2 cases per 10 million inhabitants per year with a variation between 0.2% to 8% of all the melanomas and 0.5% of all the malignant neoplasias of the oral cavity.1 Oral conditions with increased melanin pigmentation are common; however, melanocytic hyperplasias are rare. The relative incidence amongst mucosal neoplasms of the head and neck had been reviewed by Hormia and Vuori2, about 7253 cases of malignancies of upper respiratory and gastrointestinal tracts between 1953-1964, five cases of oral melanoma were found with an incidence of 0.07%. Although, the melanocytic density has regional variation, facial skin has the greatest number of melanocytes. In oral mucosa, melanocytes 1: 10 basal cells, is seen.3 Cutaneous melanomas are etiologically linked to sun exposure, however risk factors for mucosal melanomas are unknown. They have no apparent relationship to chemical, thermal, or physical events. Intraoral melanocytic proliferations (nevi) are considered to be the potential sources of some oral melanomas. Currently, most oral melanomas are thought to arise de novo. Pathophysiology is thought to be initiated by biochemical alteration in the precursor cells. This triggers accelerated growth and invasive potential, but not necessarily progression from horizontal to vertical growth phases. In cutaneous melanomas, well-known differences exist in the biologic behaviors of the radial growth phase–melanoma (flat or macular), vertical growth phase– melanoma (mass, nodule, elevation), and vertical growth phase–melanoma with metastasis. Oral melanoma occurs more commonly in the Japanese, a male predilection exists with ratio being 2:1, and is seen to be diagnosed a decade earlier in males. The age ranges from 40 to 70 years, the average being 55 years4 and rare before 20years of age.5,6 The most frequent site is the hard palate followed by the maxillary gingiva,7,8 with rare sites being mandibular gingiva, buccal mucosa and floor of the mouth.9 Intraoral malignant melanomas are diagnosed clinically as pigmented lesion having irregular shape and outline.8 They remain asymptomatic and detected only when there is ulceration of the overlying epithelium and/or hemorrhage. This delayed detection may be the reason for the poor prognosis with the 5-year survival rate being between 15% to 38%.6,10 Invasion of the bone may occur, increasing the likelihood of metastasis. In addition, the rich vascular supply present in the oral cavity may further contribute to the dissemination of the melanomas.11