Oral Mucosal Melanoma: Some Pathobiological Considerations and an Illustrative Report of a Case

Abstract

Oral mucosal melanoma is a relatively rare malignancy with an aggressive clinico-pathological behaviour. The mean 5-year survival rate is about 15 %. It arises primarily from melanocytes found in the basal cell layer of the epithelium, but may sometimes arise from melanocytes residing in the lamina propria. The pathogenesis is complex, and few of the molecular mechanisms underlying the development of oral mucosal melanoma have been defined. The extraneous risk factors associated with oral mucosal melanoma, if any, are unknown. Oral mucosal melanomas account for about 25 % of all mucosal melanomas of the head and neck, and exhibit a profile of cytogenetic alterations, and a pathobiological behaviour and clinical course different from that of cutaneous melanomas. As they are usually painless and grow quickly, as a rule, they are diagnosed late in the course of the disease when the lesions are already large and have metastasized to regional lymph nodes. In this paper we discuss some aspects of the pathobiology of oral mucosal melanoma, and present an illustrative case report.

A Review of the Aetiopathogenesis and Clinical and Histopathological Features of Oral Mucosal Melanoma

“…However, this is not true as metastatic melanoma cells can show junctional activity [6], and primary melanoma cells originating from immature melanocytes residing in the lamina propria may proliferate and invade deeply without anything resembling intraepithelial or junctional activity [14]. To further complicate matters, if in a subject with cutaneous melanoma oral mucosal melanoma was subsequently to develop, it might be assumed that this must be metastatic from the cutaneous melanoma; but it may well be an independent second primary tumour.…”

Physiological oral melanin pigmentation in a South African sample: A clinical study

“…During embryogenesis, melanocyte precursor cells migrate from the neural crest to the basal cell layers of the epidermis and of mucous membranes where they ultimately mature into melanocytes . However, as a result of arrest in their migration from the neural crest, some melanocyte precursors might become resident in the lamina propia/dermis …”

Oral mucosal melanoma

“…For unknown reasons, OMM more frequently affects Blacks, American Indians and Japanese, than Whites (Caucasians). 2,26,28,29,34,38,39 Despite the fact that this laboratory provides services to all Blacks, Whites and minority ethnic groups, in this case series, 94% of the persons with OMM were Black. To the best of our knowledge, the prevalence of OMM among Blacks and Whites in South Africa is unknown.…”

“…4,26,41,42 The 5-year survival rate of OMM is poor (15-20%), with a mean survival time of 2 years. 2,43 Larger size at diagnosis, a deeper invasive front, higher mitotic rates, vascular or neural invasion, upregulation of expression of vascular endothelial growth factor, hypoxia-inducible factor 1-alpha and CD34 at the invasion front, aberrant expression of p53 protein and loss of expression of p16 are some of the clinical, microscopical and molecular factors associated with poor prognosis. 9,44,45 Histopathologically, OMM are classified as in situ in which the tumour is limited to the epithelium and the epithelial-connective tissue interface; invasive in which the melanoma cells have invaded the lamina propria or beyond; and a combined pattern in which parts of the lesion are in situ and parts have become invasive.…”