|Year : 2015 | Volume
| Issue : 2 | Page : 136-139
Palisaded encapsulated neuroma
Adesh S Manchanda1, Ramandeep Singh Narang1, Geetika Puri2
1 Department of Oral Pathology and Microbiology, Sri Guru Ram Das Institute of Dental Sciences and Research, Amritsar, Punjab, India
2 Department of BDS, Amritsar, Punjab, India
|Date of Web Publication||17-Nov-2015|
Dr. Ramandeep Singh Narang
Department of Oral Pathology and Microbiology, Sri Guru Ram Das Institute of Dental Sciences and Research, Amritsar, Punjab
Source of Support: None, Conflict of Interest: None
Palisaded encapsulated neuroma (PEN) is a benign cutaneous or mucosal neural tumor which, usually, presents as a solitary, firm, asymptomatic, papule or nodule showing striking predilection for the face. It occurs commonly in middle age, and there is no sex predilection. Oral PEN are not common, and these lesions must be distinguished from other peripheral nerve sheath tumors such as the neurofibroma, neurilemma (schwannoma), and traumatic neuroma. The major challenge in dealing with lesions of PEN is to avoid the misdiagnosis of neural tumors that may be associated with systemic syndromes such as neurofibromatosis and multiple endocrine neoplasia syndrome type 2B. Here, we present a case of benign PEN of the gingiva in the left anterior mandibular region, laying importance on immunohistochemical staining in diagnosing such lesions.
Keywords: Benign, encapsulated, immunohistochemistry, nerve sheath, neuroma, palisaded
|How to cite this article:|
Manchanda AS, Narang RS, Puri G. Palisaded encapsulated neuroma
. J Orofac Sci 2015;7:136-9
| Introduction|| |
Tumors arising from peripheral nerves in the oral and paraoral tissues are not common. Oral peripheral nerve sheath tumors are rare , and include neurofibroma, schwannoma, palisaded encapsulated neuroma (PEN), nerve sheath myxoma, mucosal neuroma associated with multiple endocrine neoplasia type 2B, traumatic neuroma, granular cell tumor. , PEN is a distinctive benign neural tumor which usually presents as a small, solitary, asymptomatic, papule or nodule that has histologic appearance between that of neurofibroma and a schwannoma situated predominantly in dermis. 
Reed et al.  first described 44 cases of a distinctive neural tumor; which they named PEN of skin.  The first convincing evidence of intraoral PEN was described by Fletcher  in a report of a case arising on the tongue and he noted that most lesions are not fully encapsulated and showed only focally palisading pattern histopathologically. He proposed the alternate designation; solitary circumscribed neuroma (SCN) for such a lesion. 
Regarding the pathogenesis of PEN; it remains a matter of debate. The cause is uncertain, but trauma may play an etiologic role in some cases.  Irrespective of terminology; PEN are regarded as hyperplasia of nerve fibers, axons and their sheath cells akin to traumatic (amputation) neuroma.  Hence, this tumor is generally considered to represent a reactive (hamartomatous) lesion rather than a neoplasm. 
Clinically, PEN occurs as superficially situated nodules which are small, firm and often painless in nature. Majority of these occur on skin and mucosal sites such as glans penis, nasal fossa and mouth. ,, It shows striking predilection for the face.  Oral lesions are second most frequent; with predilection for hard palate and maxillary labial mucosa. 
Here, we report a case of PEN in a 40-year-old female with emphasis on the needs and challenges for diagnosing such lesions as they have to be differentiated from other peripheral nerve sheath tumors.
| Case Report|| |
A 40-year-old female reported to the department of oral diagnosis with the chief complaint of growth in left lower anterior region of the jaw since 6 months. On examination, a solitary growth was seen at the attached gingiva on the labial aspect of #31 to #33 region [Figure 1]. The growth was initially small in size and gradually increased to attain the present size of 3 cm × 2 cm. The growth was pale pink in color, pedunculated and roughly oval in shape with normal overlying mucosa and no ulceration. On palpation, growth was nontender and firm in consistency. There were no secondary changes associated with the growth. Rest of the head and neck examination was normal. Radiographic findings (intraoral periapical X-ray) revealed mild widening of periodontal ligament space in respect to #32 and horizontal alveolar bone loss in respect to all associated teeth [Figure 2].
|Figure 1: Solitary, pedunculated growth on labial aspect of gingival extending from #31 to #33 region|
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|Figure 2: Intraoral periapical showing mild periodontal ligament widening of #32|
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Correlating with the clinical and radiological findings, a provisional diagnosis of fibroma was given. A differential diagnosis of giant cell epulis, pyogenic granuloma, and neural tumor was considered due to the similar clinical appearance and site of occurrence.
Routine blood investigations were normal. An excisional biopsy was done under local anesthesia and specimen was sent for histopathological examination. Histopathological examination revealed a well circumscribed encapsulated tumor mass consisting of spindle-shaped cells with wavy nuclei [Figure 3]. The nuclei showed palisading arrangement of the tumor cells with no verocay bodies or fascicular arrangement [Figure 4]. Few nerve fascicles were present in the periphery. Tumor cells did not show any pleomorphism or mitotic activity. The overlying stratified squamous epithelium was atrophic in nature. Based on the above findings a diagnosis of a nerve sheath tumor was arrived at. The absence of bundles of collagen fibers, giant cells and vascularity with proliferating endothelial cells ruled out the diagnosis of fibroma, giant cell epulis and pyogenic granuloma respectively. However based on histopathology, neurofibroma, neuroma, schwannoma and PEN could not be differentiated.
|Figure 3: Well-circumscribed encapsulated tumor mass consisting of spindle shaped cells with wavy nuclei (H and E, ×10)|
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|Figure 4: Wavy nuclei showed palisading arrangement of the tumor cells (H and E, ×40)|
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So to know the exact nature of the mass and to arrive at a conclusive diagnosis, immunohistochemical (IHC) staining was performed with BioGenex, CA, USA, dilution 1:80 kit. IHC analysis revealed that tumor cells stained positive for S-100 and vimentin [Figure 5] and [Figure 6] and negative for desmin and glial fibrillary acidic protein (GFAP) [Figure 7] and [Figure 8].
|Figure 6: Tumor cells showing positive stain for vimentin (H and E, ×40)|
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|Figure 7: Tumor cells showing negative stain for glial fibrillary acidic protein (H and E, ×40)|
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Based on these findings; a definitive diagnosis of PEN was suggested.
| Discussion|| |
Palisaded encapsulated neuroma; also known as SCN is a clinically distinctive, solitary, benign cutaneous or mucosal tumor that is most often found on the face or close to the mucocutaneous junction. , There is no sex preponderance, and the lesion is most frequently diagnosed between the fifth and seventh decades of life, although tumor often has been present for many months or years. 
Clinically, these lesions are solitary, sessile, firm, pink or flesh colored, dome-shaped. Size of the lesion, usually, varies between 2 and 6 mm ,, with a slow progression in the growth of tumor seen over a number of years. Multiple lesions are rarely found.  No hairs are seen growing on the surface of cutaneous lesions with minimal or absent telangiectasia. Oral PEN represents only 0.05% of all peripheral neural tumors present intraorally. ,
Histologically; appearance is characteristic, and tumor appear well circumscribed. Tumor consists of partially encapsulated mass of moderately cellular interlacing fascicles of spindle cells that are consistent with Schwann cells. Tumor cells are poorly delineated with eosinophilic cytoplasm. Basophilic nuclei are characteristically wavy and pointed with no significant pleomorphism or mitotic activity. ,,, Palisading of nuclei is also seen. Occasional small blood vessels are seen in stroma. These features were in accordance with the histopathologic features in the present case. Lesion is often unilobular and exhibit smooth contours. Nodular type is most frequently seen with other less common variants reported-plexiform, fungating, multinodular, epitheloid growth pattern. ,
Since there are similarities and overlap in features of peripheral nerve sheath tumors; a histologic co-relation along with IHC staining is needed to arrive at a definitive diagnosis.
Lesions of PEN must be differentiated from neurofibroma, schwannoma, traumatic neuroma, leiomyoma [Table 1]. ,,,
|Table 1: Histopathological features and IHC characteristics of PEN and lesions included in its differential diagnosis|
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Immunohistochemical analysis of PEN reveals; presence of numerous axons within tumor and cells show a positive IHC reaction for S-100 protein, collagen type IV and vimentin; all of which are consistent with Schwann cell differentiation. , Neurites are neurofilament protein positive and GFAP negative. Axons to Schwann cell ratio is <1:2.  In the present case; IHC staining of the tumor cells was positive for S-100 protein and vimentin and negative for GFAP.
Treatment of PEN consists of conservative local surgical excision.  The importance of correctly diagnosing these tumors is that a misdiagnosis of such lesions as a neurofibroma or mucosal neuroma may lead to unnecessary clinical concern or patient testing.
| Conclusion|| |
The present case highlights the perplexity in diagnosing a lesion of peripheral nerve sheath origin. Problems of differential diagnosis concern a wide range of other tumors with the same origin such as the neurofibroma, schwannoma, and traumatic neuroma. IHC analysis serves to be helpful so that a definitive diagnosis of PEN can be made.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]