Solitary neurofibroma of the oral mucosa: a previously undescribed variant of neurofibroma.

We report a distinct morphologic type of neurofibroma, lipomatous neurofibroma, arising in the oral mucosa, which has not been described previously in the literature. A 25-year-old female patient presented with a solitary mucosal mass on the palatal gingiva. Although the limited biopsy material was diagnosed as a spindle cell lipoma, characteristic light microscopic neurofibromatous areas, intricately admixed with mature fat, were found in the entire resection specimen. Immunohistochemically, many of the spindle cells were positive, either diffusely or focally, for common neural markers, with patchy staining for CD34 and epithelial membrane antigen. S-100 protein was also positive in adipocytes. Ultrastructural examination confirmed the diagnosis of neurofibroma and suggested an intimate relationship between neoplastic neural cells and adipocytes.