Primary Gingival Mucosal Melanoma: A Case Report and Comparison With Cutaneous Melanoma

Mucosal melanoma (MM) is a rare and highly aggressive malignancy arising from melanocytes located within mucosal surfaces. Unlike cutaneous melanoma (CM), MM develops in non-sun-exposed mucosa, frequently harbors KIT or SF3B1 mutations, demonstrates a lower tumor mutational burden, and exhibits reduced responsiveness to immunotherapy. These biological differences distinguish MM from CM and contribute to important differences in staging, prognosis, and management. We describe the case of a 71-year-old male who presented with a newly identified pigmented lesion involving the right inferior gingival mucosa. His medical history included type 2 diabetes mellitus, dyslipidemia, and essential hypertension. Biopsy confirmed malignant MM. Positron emission tomography/computed tomography (PET/CT) demonstrated a 1.3 × 1.2 cm fluorodeoxyglucose-avid lesion (SUV max 9.6) without evidence of mandibular invasion, cervical nodal disease, or distant metastasis. The patient underwent radical excision of the lesion with right selective neck dissection (levels I-III). Histopathologic examination confirmed MM (pT3N1) with positive deep margins and metastatic involvement of two regional lymph nodes. This case highlights the diagnostic and therapeutic challenges of oral MM and emphasizes the importance of recognizing the biological and clinical differences between MM and CM. Routine, thorough intraoral soft-tissue examination and early biopsy of suspicious pigmented oral lesions are essential to facilitate timely diagnosis and management of this aggressive malignancy.