Melanoma of the oral cavity: pathogenesis, dermoscopy, clinical features, staging and management

Abstract

Primary mucosal melanoma of the oral cavity is an exceedingly rare neoplasm which is estimated to comprise 1-2% of all oral malignancies. In contrast to cutaneous melanomas, the risk factors and pathogenesis are poorly understood. The predominate localization of primary oral melanoma is hard palate and maxillary alveolus. Dermoscopy may be utilized as an adjunctive tool in the clinical differential diagnosis of oral mucosal melanoma whenever the lesion is accessible with a dermoscope. Surgery is the mainstay of treatment, but it may be challenging depending on the location of the tumor within the oral cavity and its size. Adjuvant therapy with dacarbazine, platinum analogs, nitrosoureas and interleukin-2 have been utilized with low response rates. Imatinib may be effective for patients with with c-Kit gene mutations. Sunitinib and dasatinib have been reported effective in selected cases. Vemurafenib and dabrafenib are targeted agents for patients with BRAF mutation-positive melanoma. Ipilimumab, an anti-cytotoxic T-lymphocyte antigen 4 antibody and pembrolizumab, a monoclonal antibody targeting programmed death 1 receptor may be a feasible treatment option in patients with metastatic mucosal melanoma.

Keywords: dermoscopy; head and neck cancer; head and neck melanoma; mucosal melanoma; oral cancer.

Figure 1

Melanoma of the oral mucous membranes.

Figure 2

The multicomponent pattern is the most common dermoscopy pattern in mucosal melanoma. The image shows an asymmetric lesion with multiple colors (white, light brown, dark brown, black grey-blue, red), dots (arrows), blotches (double arrows), blue-whitish area (triangle), peppering (#) and areas of regression (stars). Reproduced from Lin et al.[37] with permission.

Figure 3

An amalgam tatoo is a frequent melanoma imitator in oral mucous membranes.

Figure 4

Dermoscopy of an amalgam tattoo. Dermoscopy image showing a homogenous, slightly grainy bluish lesion may allow in vivo distinction of oral an amalgam tattoo from melanoma. Nodular lesions should be excised regardless of dermoscopy results. In the case of superficial lesions dermoscopy may allow to exclude melanoma and avoid unnecessary excisional biopsies. In such cases the lesions should be monitored.