[Primitive malignant melanoma of the base of the tongue]

Abstract

Although the incidence of malignant cutaneous melanoma has doubled each decade since the early 1960s, the mucous counterpart is still rare, representing 1.4% of all melanomas in caucasian patients. In the oral cavity this incidence is even higher, ranging from 0.2% to 8.0% of all melanomas. However, it is unusual for the primary location to be in the tongue and only 25 such cases have been reported in the literature. In 1974, Conley, reviewing 52 melanomas of the mucous membranes of the head and neck, observed that "it is curious that no melanomas occurred in the tongue". The prognosis for mucosal melanomas is clearly worse than for cutaneous melanoma, with most authors reporting a 5-year survival rate of 10-25%. It is not clear whether mucosal melanomas are biologically more aggressive than their cutaneous counterparts or if prognosis is simply related to the fact that they are normally more advanced at the time of diagnosis. In fact, it is clear that the etiologic and pathogenetic basis for the origin of mucosal melanomas, as well as of their treatment and prognosis, is not understood nearly as well as that of cutaneous melanomas. Historically, cutaneous melanoma has been characterized as radio-resistant, although recent observations regarding the radiobiological and clinical responses have prompted investigators to re-evaluate the role of radiotherapy in localized mucosal melanoma. The authors report a primary malignant melanoma of the tongue base, heavily pigmented, rather bulky and nodular, approximately 0.4 cm in size, very similar to one of the varices usually encountered in this portion of the tongue. The patient came to the authors' observation complaining of peripheral vertigo. The melanoma was suspected due to a pulmonary metastasis observed in a routine chest X-ray and after a thorough search for the possible primary neoplasm. Because of widespread metastases, the patient was not treated with radio or chemotherapy and died 8 weeks after surgical ablation of the primary lesion. As observed by Batsakis, at least 25% of mucosal melanomas are clinically identical to innocent lesions. For this reason, the authors stress the importance of taking into consideration the possibility of mucosal melanoma in the differential diagnosis of head and neck neoplasms and of being suspicious of lesions which appear clinically insignificant.