Palisaded Encapsulated (“Solitary Circumscribed”) Neuroma of the Oral Cavity: A Review of 55 Cases

Abstract

We describe the clinicopathologic characteristics of 55 oral palisaded encapsulated (solitary circumscribed) neuromas (PEN/SCN). Fifty-five cases of PEN/SCN in 54 patients were reviewed. Lesions were categorized according to their histologic pattern, partial or complete encapsulation, presence of Verocay bodies and presence of a parent peripheral nerve. In 13 selected cases immunohistochemical evaluation for neuronal markers (S-100, GFAP, NFP, EMA) was performed. When immunoreaction with EMA was weak, claudin-1 and glut-1 stains were utilized. Thirty-eight patients were men and 16 were women. Mean patient age was 48 years (SD: +/-14). The vast majority involved the masticatory (palate and gingiva) mucosa (76.4%) followed by the labial mucosa, the tongue and buccal mucosa. Recurrence was recorded in only one case. Histologically, 34 lesions had a lobular pattern, 10 were plexiform, 7 fungating and 4 multilobular. Stroma was limited, but focal myxoid changes were seen at the periphery of the lobules. Only one predominantly myxoid lesion was encountered. The number of intralesional axons varied, but the ratio of Schwann cells to axons was generally less than 1:2. Most lesions (89%) were only partially surrounded by perineurium. Tumor cells were S-100 positive and GFAP negative. The parent nerve was identified in 50% of the cases. Overlying epithelium was generally atrophic. Peritumoral connective tissue was generally unremarkable, but chronic inflammation was present in five cases. PEN/SCN is a relatively common peripheral nerve sheath tumor. Generally, its diagnosis is simple. GFAP may be of help to distinguish PEN/SCN from other peripheral nerve sheath tumors (schwannoma, neurofibroma, traumatic neuroma) in cases where histomorphologic features may be confusing. Finally, pathologists should be aware of the occurrence of plexiform and multilobular PEN/SCN variants, to avoid misinterpretation as plexiform neurofibroma or schwannoma.

Palisaded encapsulated neuroma of the upper lip

“…The mean age of PEN on the oral mucosa was between 37 to 54 years [3,4,7,8] and it was almost the same tendency that of the skin's as between 40 and 60 years [2]. As for sex difference, men were almost predominant to women [3,7,8].…”

“…The incidence rate of PEN in the oral mucosal biopsy specimens were 0.04% to 0.05% in the previous reports [4,7], and PEN accounts for approximately 22% to 25% of all peripheral nerve origin in the oral cavity [4,7]. The mean age of PEN on the oral mucosa was between 37 to 54 years [3,4,7,8] and it was almost the same tendency that of the skin's as between 40 and 60 years [2]. As for sex difference, men were almost predominant to women [3,7,8].…”

“…Clinically, all tumors were nodular in appearance [3] with small and most often painless [3]. Multifocal lesions were rare.…”

“…Multifocal lesions were rare. The tumor were solitary, sessile, firm, normal mucosal colored, between 2 to 6 mm of diameter, and the size of which never exceeded 1.0 cm in greatest dimension [3]. The most common clinical diagnosis was "focal fibrous hyperplasia (fibroma)" [7].…”

“…The majority of PEN was occured in the oral mucosa with the most frequent [3]. In the mucosal lesion, other literatures expressed that PEN had occurred on the mucocutaneous junctions, for example, eyelid, nasal fossa, and oral mucosa overwhelmingly in the face, on the contrary [4][5][6].…”