Malignant melanoma of the oral mucosa in a 17-year-old adolescent girl.

Mucosal melanomas of the oral cavity are rarely seen in the United States. The hard palate is the most common intraoral site. This unusual case occurred in the oral cavity of a 17-year-old Asian girl, who presented to her dentist with complaints of pain and swelling in the upper jaw. The lesion was distal and palatal to the maxillary left second molar, which was vital. Interestingly, the clinical presentation was a hyperplastic, tender lesion that bled when probed. Histopathologically, the biopsy demonstrated a sheet of spindle-shaped cells arranged in nests and fascicles. The nuclei were vesicular, oval to spindle-shaped, and some contained nucleoli that were distinguishable but not prominent. No melanin pigment was observed in the lesion. Tumor cells strongly expressed S100 protein, gp100 (HMB-45), and microphthalmia transcription factor, and variably expressed MART1, but not cytokeratins, CD34, or muscle-specific actin. The histopathologic features and immunohistochemical findings are consistent with a diagnosis of malignant melanoma.