Introduction

Primary malignant melanomas of the head and neck are rare constituting approximately 1-2 % of all melanomas (₁,₂). Half of the head and neck melanomas occur in the oral cavity, followed by the nasal cavity (44%) and sinuses (8%) (₃). The age range for patients with oral melanoma is from 40 to 70 years; the avarage age is 55 years (₂,₃,₄). Oral melanoma appears to be slightly more common in men than in women, and the most frequent sites of occurence are the hard palate and the maxillary gingiva (₂,₄,₅,₆).

Melanoma of the oral mucosa is less common than cutaneous melanoma (₇). Due to its rarity, the origin of oral melanomas and the risk factors are largely unknown (₄). Certain races may be more commonly affected: the Japanase (₈), black Africans (₉), native Americans (₁₀) and Hispanics (₁₁). At the site of oral melanoma, asymptomatic pigmentation areas or nevi are noted before diagnosis in approximately one third of patients (₅,₁₂,₁₃,₁₄). Intraoral melanomas are usually darkish brown to black in color, but amelanotic lesions have also been reported (₁). Most oral melanomas present as solitary lesions, however, multiple or synchronous lesions have also been reported (₁₅).

Case Report

An 65-year-old edentulous woman who has been using total denture for 20 years presented with a 10-day history of a rapidly enlarging, painless, 2 cm in diameter, pigmented but not uniform lesion raising from mucosa on the hard palate (Fig.1). There was a cushion in the maxillar denture (Fig.2). The patient had no known history of any prexisting nevus. More posteriorly, melanotic satellite areas were observed.

Figure 1

Figure 1: Primary malignant melanoma of oral cavity. There are satellite lesions (see arrows).

Figure 2

Figure 2: The upper denture of the patient. Note the cushion within the denture (see arrow).

There was no lymphadenopathy and hepatosplenomegaly or any abnormal systemic sign. The patient was not smoker and drinker. Chest X-ray, bone scan and body computed tomography scan were within normal limits. According to subperiosteal exicional biopsy, the diagnosis was malign melanoma.

Histopathologically, the biopsy revealed a downward streaming in the dermis of the tumor cells (Fig.3). There were strikingly atypical melanocytes arranging as solitary units, irregular cords and nests. A proliferation of neoplastic cells exhibited a wide variety of shapes, including spindle, plasmacytoid, and epithelioid forms. With higher magnification, nuclei were seen to be atypical and cytoplasm abundant and eosin staining. Mitotic activity and pigmented areas were observed at various tissue levels (Fig.4). Immunohistochemistry was used to establish the final diagnosis. The tumor cells strongly expressed S100 protein and GP100 (HMB-45) antibodies (Fig.5).

Figure 3

Figure 3:Downward streaming in the dermis of the tumor cells (40X)

Figure 4

Figure 4: Mitotic activity and pigmented areas were observed at various tissue levels (200X)

Figure 5

Figure 5: The tumor cells strongly expressed S100 protein and GP100 (HMB-45) antibodies (40X)

With the diagnosis of malignant melanoma, the patient was referred to Radiation Oncology Department for treatment. Radiotherapy was administered to the patient.

Discussion

The International Union Against Cancer (IUAC) has no proposed clinical TNM classification for malignant melanoma, but Westbury (₁₆,₁₇) describes a clinical classification: I-primary tumor presents only, II-metastases present (IIa-adjacent skin involved, IIb-regional lymph nodes involved), III-metastases beyond regional nodes. Our case falls into the classification of IIa because satellite lesions were present.

There is a general agreement that surgery is the treatment of choice for oral malignant melanoma. Most authors advocate wide local exicion of the lesions, with or without lymph node dissections. Although it is generally agreed that melanomas are not radiosensitive (₅,₁₂), due to an anatomic restriction for our patient, it was decided radiotherapy as treatment modality.

Possible etiologic factors for oral melanoma are mechanical trauma ,ill-fitting dentures, oral habits, self medication and exposure to formaldehyde (₁₂). Since our patient has been using total denture with cushion, melanoma may be originated from mechanical trauma.

Correspondence to

Binali CAKUR, DDS PhD Department of Oral Diagnosis and Oral Radiology, Faculty of Dentistry, Atatürk University, Erzurum, Turkey Business telephone number: 0090.442.2311765 Fax number: 0090.442.2360945 E-mail address: bcakur@ atauni.edu.tr