Case Report: Melanoma of the hard palate presenting initially with gastrointestinal symptoms: the diagnostic pivotal role of 18F-FDG PET/CT.

Mucosal melanoma (MM) of the oral cavity, particularly involving the hard palate, is an exceedingly rare and aggressive malignancy. Due to its insidious onset and non-specific early manifestations, diagnostic delays are common. We report a unique case of a patient primarily presenting with chronic gastrointestinal discomfort. Subsequent whole-body 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) imaging identified a hypermetabolic primary lesion in the hard palate, alongside extensive systemic metastases, which was further confirmed by histopathological and immunohistochemical analysis. This case underscores the high sensitivity of 18F-FDG PET/CT in detecting occult primary mucosal melanomas and emphasizes its critical value in the comprehensive staging and management of rare malignancies.