Palisaded encapsulated neuroma of the upper lip

Palisaded encapsulated neuroma (PEN; solitary circumscribed neuroma) is a benign and hyperplastic lesion consisting of Schwann cells. PEN of the lower lip was reported by Tomich and Moll [1] 35 years ago. However, the accumulation of the information about PEN which occurred in the oral mucosa was not enough. This article describes a case of a PEN on the upper lip of a 41-year-old woman. The lesion with 0.7 cm diameter was performed excisional biopsy. Histologically, the tumor was almost circumscribed by thin fibrous capsule, and consisted of diffusely and dense proliferation of the spindle shape cells arranged in interlacing fascicles. Focal suggestions of nuclear palisaded growth were indicated within the tumor. Immunohistochemicallly, the fascicles of tumor cells were positive for S-100 protein, and vimentin and negative for α-actin and GFAP. A few numbers of axons were demonstrated by anti-neurofilament antibody in this lesion. Therefore, the definitive diagnosis was PEN.