Dermatology Online Journal

Oral melanoma: An unusual presentation
Nara Lidia Lessa DDS¹, Andrea Braga Moleri DDS², Flavio Merly DDS², Luiz Carlos Moreira DDS³, Mirian Jordao Moreira DDS³, Heliton Spindola Antunes DDS^{2, 4}
Dermatology Online Journal 14 (1): 17

1. Universidade do Grande Rio, (UNIGRANRIO), Brasil. 2. Department of Stomatology, School of Dentistry, UNIGRANRIO, Brasil 3. Department of Buccal Diagnostic, Universidade Federal Fluminense (UFF), Brasil 4. Clinical Research Service, Instituto Nacional de Cancer (INCA), Brasil

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Abstract

Melanoma of the oral cavity is a rare malignant disease that is often discovered in an advanced stage; survival time is an average of five years. Oral melanoma makes up from 0.2 to 8 percent of all melanomas. The presentation of this clinical case demonstrates the complexity of clinical and histopathological manifestations and poor prognosis of oral melanoma.

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Melanoma located in the oral cavity represents 0.5 percent of all oral malignant conditions. Primary melanoma in the oral cavity is rare, making up 0.2 to 8 percent of all melanomas in Europe and the USA [1, 2]. The average age of affected individuals is from 50 to 55 years [2, 3, 4], with a general range between 30 to 80 years [5, 6, 7]. However, Silva et al. presented a rare case of melanoma in the oral cavity in a 17 year old Asian girl [8]. Most cutaneous melanoma occurs in light-skinned adults; it is rare in people with dark skin [9]. However, the epidemiology of oral melanoma is different and represents a much higher percentage of melanoma found in individuals of Asian, Indian, Hispanic, and African heritage [2, 10, 11].

Clinical synopsis

A 65-year-old black woman went to the stomatology service, having as a main complaint the presence of a painless nodule located on the palate. She had noticed this nodule just 1 month prior to presentation. During examination, the patient mentioned having difficulties in using her upper dentures that she had been using for over 30 years. The patient did not smoke and had no familial cancer background.

Figure 1	Figure 2
Figure 1. A black patch that extended to cover the hard palate and involved the alveolar edge region Figure 2. Atypical melanocytes with fine melanin granules are noted extending into the connective tissue.

Under the upper denture, a black patch covered most of the hard palate and extended onto the alveolar ridge. The patch was asymmetric with irregular edges and color variation; black was the predominant color. A nodule with firm consistency was present on the left side of the patch. The nodule was red, not bleeding, and painless (Fig. 1). There was no palpable lymphadenopathy.

Two incisional biopsies were performed. The nodule was excised and an additional incisional biopsy was performed in a macular area. Melanoma was diagnosed on histology; atypical melanocytes were observed in the connective tissue as loosely aggregated cords or sheets of pleomorphic cells (Fig. 2). Immunohistochemical studies showing HMB-45, S-100 protein and Melan A reactivity of lesional cells identified the malignant cells as melanocytes.

Discussion

Oral melanoma is generally included in the category of acral-lentiginous melanoma. It occurs most frequently in the maxilla, with the palate as a common site (32% incidence). The maxillary gum is the second most frequent area of incidence (16 %). Other affected regions in descending order of incidence are buccal mucosa, mandibular gingiva, lips, tongue, and buccal floor [2, 12, 13, 14]. This neoplasia is more frequent in men than women, in a proportion of 2:1 [2, 5, 9, 10, 12, 15]. However, this proportion may vary depending on the geographic location; in England oral melanoma is more frequent in women (2.5: 1) [13]. Oral melanoma has a unfavorable prognosis compared to the cutaneous melanoma, probably because of the delay in diagnosis [16, 17].

Clinical characteristics

Oral melanoma may be associated with a pre-existing hyperpigmentation

[1, 12, 15]. Early, it presents as a brown to black macule; later it may develop a nodule or ulceration. Asymmetry and irregular borders are clues to the diagnosis [2]. Oral melanoma can often be identified by the same ABCD criteria as cutaneous melanoma [3, 2, 9]. However, once detected (often late), oral melanoma frequently exhibits an extremely invasive behavior, with vertical growth, high index of metastasis, and poor prognosis [9].

The oral and cutaneous melanomas have similar histopathology and specific immunocytochemical studies (S-100, Melan A, and HMB-45) are often helpful [1,3,12,18]. However, there are some specific melanocytic mucosal entities that must be differentiated.

Differential diagnosis

Pigmented lesions of the oral mucosa are clinically classified as

multi-focal pigmented macule. This entity may be diffuse and includes physiological pigmentation in dark-skinned people, melanosis associated with smoking, and melanosis induced by medication and heavy metals. Another entity is single focus pigmentation, including melanotic macule, amalgam tattoo, melanocytic nevus, melanocarcinoma, and melanoma [1, 7, 13, 19, 20]. In a study by Fernandez et al. of 155 patients with pigmented mucosal lesions, incisional biopsies determined that 65.2 percent were benign melanocytic nevus [20].

Diagnosis and prognosis

Excisonal biopsy of small lesions and incisional biopsy of large lesions should be accomplished [2, 6, 7, 9, 10, 15]. Little, recommends an excisional biopsy for small lesions less than 1.5 cm in diameter [9].

The prognosis for oral melanoma is extremely poor and is determined by the thickness of the melanoma at the time of diagnosis [5, 7, 10, 13, 21]. The survival average for patients with oral melanoma is about 5 years, although in 5 percent of affected patients it is just 1-2 years [ 22].

Conclusion

It is essential to include oral examination in full body skin examinations; dentures should be removed for examination. Suspicious pigmented and non-pigmented lesions should be biopsied appropriately.

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