Oral Amelanotic Melanomas: Clinicopathologic Features of 8 Cases and Review of the Literature

Abstract

Mucosal melanomas are aggressive tumors, rarely observed in the oral cavity. The diagnosis is based on the clinical and microscopical features. Often these tumors had variable amounts of melanin pigmentation. However, when melanin is absent, the tumors are denominated amelanotic, presenting a tendency to misdiagnosis and delayed treatment. The aim of this study was to describe the clinicopathologic features of a series of oral amelanotic melanomas (OAM). Records of all cases of OAM were retrospectively retrieved from oral pathology services from January 2002 to January 2019. Data regarding the clinical features, morphological aspects, immunohistochemical reactions, treatment, and follow-up status were collected. Eight cases of OAM were included, 6 in men and 2 in women (ratio of 3:1) ranging in age from 33 to 77 years (mean 53.6 years). Clinically, the tumors presented as masses or ulcerated swellings. The most common intraoral locations of the tumors were gingiva and palate. Cervical lymph node metastasis was detected in 3 patients at the first examination. All but one patient died from complications of the tumors after a mean follow-up period of 8.5 months. In conclusion, OAM is a very aggressive malignant tumor, and when melanin is absent, an immunohistochemical panel comprising S100, melan A, HMB45, and SOX10 should be performed.

Primary melanoma of the oral cavity: A multi-institutional retrospective analysis in Brazil

“…However, amelanotic melanomas, such as case 5, present a challenge to clinical diagnosis. The absence of melanin pigmentation makes the clinical diagnosis of these tumors extremely challenging due to the clinical similarity with several other conditions that affect the oral cavity, including infectious diseases, non-neoplastic proliferative processes, reaction lesions, and other oral malignancies ( 1 ).…”

“…When melanin pigmentation is present, OM can usually be easily diagnosed by morphological analysis ( 6 ). However, when the lesion is amelanotic, such as in case 5, the immunohistochemistry analysis is essential to establish the correct diagnosis ( 1 , 5 ). In both situations, positive immunohistochemical reactions for S-100 protein, HMB-45, and Melan A confirm the diagnosis of OM ( 1 , 6 , 23 ), as occurred in our series.…”

“…Primary melanoma of the oral cavity is rare and corresponds to 2 to 8% of all melanomas ( 1 ) and about 0.5% of all malignancies of the oral cavity, with an incidence of 1.2 cases per 10 million individuals per year ( 2 ). Oral melanoma (OM) tends to occur in adults between the fifth and sixth decades of life.…”

“…In recent years, there has been a significant improvement in the survival of patients with melanoma, mainly due to the early detection of the tumor and new immunotherapeutic drugs ( 4 ). However, when melanoma occurs in the oral cavity, lesions in the early stages can mimic the clinical appearance of several other conditions making clinical diagnosis difficult ( 5 ), what contributes to that OMs are usually diagnosed in advanced stages, worsening the prognosis and contributing to the high mortality rates of this cancer ( 1 , 5 ).…”

“…There are few Brazilian studies published in the English-language literature on OM to date ( 1 , 4 , 9 - 11 ), especially multi-institutional studies conducted in oral pathology services. Thus, this study aims to describe the clinicopathologic, and immunohistochemical features of 7 new cases of OM retrieved from two centers of oral pathology and medicine located in Brazil and to compare the findings with epidemiological data from different geographic locations.…”