Oral Malignant Melanoma Initially Misdiagnosed as a Racial Pigmentation: A Case Report

Abstract

Oral malignant melanoma (OMM) is rare, representing less than 0.5% of all oral malignancies. The most affected sites are the palate and the maxillary gingiva. Histological examination is important to establish the diagnosis of any suspicious pigmented lesion in the oral cavity, mainly if a precise clinical diagnosis is not possible. We present one case of OMM that was initially diagnosed as a racial pigmentation elsewhere 2 years earlier. Clinical examination showed multiple macules and nodules located on the hard and soft palate, gingiva and superior alveolar mucosa. These lesions were painless and presented a color variation going from dark blue to black. Histological analysis showed sheets and nests of atypical melanocytes displaying a range of shapes such as plasmacytoid, epithelioid, and round cells, located in the superficial corium extending to the deep tissues. A few tumor cells contained variable amounts of melanin. There was no invasion of blood vessels or nerve fibers. Immunohistochemical analysis revealed that the neoplastic cells were positive for HMB-45, melan-A, S-100 and negative for AE1/AE3, confirming the diagnosis of melanoma. The Ki-67 labeling index was around 25%. The patient refused any treatment and died 11 months later.

Solitary Pigmented Melanocytic Lesion on the Palatal and Gingival Mucosa: Should It Rise Dentist’s Concerns?

“…A followup visit was then encouraged to further observe the lesion since there was a report of delayed diagnosis of OMM which previously was thought to be a racial pigmentation. 9 The diagnosis of racial pigmentation on the previous report was only based on the clinical aspect of the lesion. Based on the experience from this case, the dentist's awareness regarding the possible finding of potentially malignant pigmented lesion with asymptomatic nature still needs to be increased.…”

“…Furthermore, its appearance could be complicated by the presence ulceration and bleeding. 2,9,12 The examination on the lesion's ABCD checklist (asymmetry, border irregularities, color variegation and diameter > 6mm) as for cutaneous melanoma could also be used for the clinical diagnosis of OMM. 14 The growth characteristics of OMM could be initiated by long period of radial growth phase followed by vertical growth phase or in other types aggressive vertical growth phase could start from the beginning of the disease.…”

“…3,15 Histopathologically, OMM may show a degree of pleomorphism with a wide variation of shapes and patterns which may be similar to other types of tumors such as lymphomas, poorly differentiated carcinomas, sarcomas, neuroendocrine carcinomas and germ-cell tumors. 9,12 The complexity of the disease is added by the fact that some OMM may be nonpigmented, making the clinical diagnosis becoming more difficult. In such cases, the immunohistochemistry analysis using S-100, HMB-45, Melan-A, and vimentin are needed to diagnose the disease accurately.…”

Melanoma of the oral mucosa: report of an aggressive case and review of the literature

“…These lesions can manifest in different circumstances, either as physiological alterations such as racial pigmentation or as systemic events such as Addison's disease. Moreover, these manifestations can also be found in rare oral neoplasms such as melanomas 1,2 .…”

“…The latter are cells derived from the neuroectoderm that produce the pigment melanin and reside in the basal layer of the epithelium 3 . Although the third most common skin cancer, melanoma is extremely rare in the oral cavity, accounting for less than 1% of all melanomas and for about 0.5% of all malignant oral tumors 2,4 .…”