Answer: Palisaded encapsulated neuroma

Histology: The surface epithelium is focally ulcerated. There is a demarcated but nonencapsulated nodular proliferation of spindled cells in the submucosa. The tumor is comprised of cellular interlacing fascicles of spindle cells that resemble Schwann cells, and they are strongly S100 positive.

The nuclei are wavy and pointed. True well formed Verocay bodies are not observed. Significant cellular atypia and mitotic figures are not observed.

Discussion: Oral palisaded encapsulated neuroma is a common oral tumor that frequently arises from the hard palate as a dome-shaped papule or nodule. They lack the intervening collagenized stroma and the haphazard nature of myelinated nerve fibers that are seen in traumatic neuromas, yet some speculate that PEN is caused by trauma. The designation PEN misses the mark of their histologic makeup as these lesions are often not encapsulated and lack the well formed Verocay palisades of neurofibromas. Attention to the marginated growth and the absence of cytologic atypia helps avoid confusion with a spindle cell melanoma.

PEN is benign and seldom recurs following excision. Of note, the PEN is not associated with neurofibromatosis or with any of the MEN syndromes.