Palisaded encapsulated neuroma of oral mucosa.

The palisaded encapsulated neuroma is a solitary, small peripheral nerve lesion that occurs primarily on the facial skin of middle-aged adults. We report a series of 13 cases of palisaded encapsulated neuroma occurring on oral mucosa. The lesions presented as solitary, firm, sessile, partly or completely encapsulated, 2 to 3 mm nodules in adults with a mean age of 51 years (median 55 years). Nine of the neuromas occurred on the hard palate; the remainder were found on the soft palate, lower lip mucosa, upper lip mucosa, and maxillary anterior alveolar ridge. None of the cases was associated with neurofibromatosis or multiple endocrine neoplasia syndrome type III. Microscopically, the tumors were characterized by a moderately cellular, fascicular proliferation of spindle cells that showed some areas of nuclear palisading, suggestive of schwannoma. Immunohistochemical stains revealed that the lesions were composed largely of S-100 protein-positive Schwann cells and variable numbers of peripheral nerve axons, which were identified by their positive neurofilament staining. The fibrous capsule of the lesions showed positive staining for epithelial membrane antigen, indicative of perineurium.