|Year : 2016 | Volume
| Issue : 4 | Page : 441-444
Intraosseous neurilemmoma of the mandible
Rupam Sinha1, Arpita Kabiraj2, Soumyabrata Sarkar1, Tanya Khaitan3
1 Department of Oral Medicine and Radiology, Haldia Institute of Dental Sciences and Research, Haldia, West Bengal, India
2 Department of Oral Pathology and Microbiology, Index Institute of Dental Sciences, Indore, Madhya Pradesh, India
3 Department of Dentistry, Murshidabad Medical College and Hospital, Berhampore, West Bengal, India
|Date of Submission||18-Mar-2016|
|Date of Acceptance||24-Dec-2016|
|Date of Web Publication||21-Feb-2017|
Dr. Arpita Kabiraj
Department of Oral Pathology and Microbiology, Index Institute of Dental Sciences, Indore, Madhya Pradesh - 452 016
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Neurilemmomas are relatively uncommon lesions most commonly encountered in the nerve sheath originating from Schwann cells. They are rarely found in the oral cavity and are characterized by solitary occurrence, slow, persistent growth and smooth surface, along with inconsistent clinical aspects depending on the nerve origin. Microscopically, the lesion typically comprises of alternating regions of hypercellularity and hypocellularity such as Antoni A and Antoni B arrangements, respectively. Here, we present a case of a benign spindle cell tumor of the mandible reflecting a case of intraosseous neurilemmoma in a 33-year-old female patient. Immunopositivity with S-100 and vimentin clearly indicates the lesion to be a spindle cell tumor with neural involvement. The prognosis was favorable; complete surgical removal was the treatment of choice with no recurrence noted. The present case further magnifies the importance of neurilemmoma and further aids in the differential diagnosis of several other benign soft tissue tumors in the oral cavity.
Keywords: Antoni A, Antoni B, immunohistochemistry, schwannomin
|How to cite this article:|
Sinha R, Kabiraj A, Sarkar S, Khaitan T. Intraosseous neurilemmoma of the mandible. J Indian Acad Oral Med Radiol 2016;28:441-4
| Introduction|| |
Neurilemmoma also known as schwannoma is a rare, benign, neurogenic tumor emerging from Schwann cells of the peripheral nerves. These types of cells are responsible for lining the myelinic nerve cells of any cranial, peripheral or autonomic nerves that contain Schwann cells., Once termed “peripheral fibroblastoma” or “neurinoma,” this benign tumor was described by Virchow in 1908 and Verocay in 1910. In 1935, the term neurilemmoma was coined by Stout. These tumors have a predilection for head and neck, extremities and the posterior mediastinum. Extracranially, 25–40% of all neurilemmomas are located in the head and neck region, however, only 1% show an intraoral origin without recurrence. Here, we present a case of a benign spindle cell tumor of mandible reflecting a case of intraosseous neurilemmoma.
| Case Report|| |
A 33-year-old female patient reported with complaint of growth in the lower left back jaw region since 6 months. The growth started 6 months earlier, gradually increased in size and slowly ulcerated over a period of time. There was no history of any discharge, numbness or paresthesia except for intermittent pain, which subsided on self-medication. Medical, dental, family and personal histories were inconspicuous, and no other abnormalities were noted on general physical and extraoral examination.
Intraoral examination revealed the presence of a solitary well-defined ulcerative growth on the left alveolar and retromolar region measuring approximately 3 × 2 cm in size [Figure 1]. Anteriorly, the growth extended from the distal aspect of 37 to the retromolar region posteriorly. Mediolaterally, it extended to the buccal mucosa up to the level of occlusion. The surface over the growth appeared keratinized showing indentations of the opposing upper posterior teeth. On palpation, the growth was tender and firm-to-hard in consistency. The growth was sessile in nature having an indurated base. Based on the history and clinical findings, a provisional diagnosis of malignant growth in the left lower alveolar region was considered.
|Figure 1: Intraoral photograph showing a solitary well-defined ulcerative growth on the left alveolar and retromolar region|
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Intraoral periapical radiograph (IOPAR) and orthopantomogram (OPG) revealed horizontally impacted 38 with ill-defined homogenous radiolucency surrounding the tooth extending towards the ramus of the mandible. This radiolucency measured approximately 3.5 × 2 cm and was surrounded by a faint radiopaque border. The lower border of mandible was found to be intact [Figure 2]. Incisional biopsy was performed, which revealed no evidence of malignancy histopathologically. Therefore, further surgical excision was advised for confirmatory diagnosis. Surgical intervention was carried out and no postoperative complications developed. The excised tissue specimen was thus sent for histopathological and immunohistochemical analysis.
|Figure 2: IOPAR and OPG revealing horizontally impacted 38 with ill-defined homogenous radiolucency surrounding the tooth extending towards the ramus of the mandible|
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Microscopically, the hematoxylin and eosin stained section showed connective tissue stroma with fibrous capsule. The connective tissue was seen to be composed of numerous scattered spindle cells arranged in fascicles and in a palisading pattern depicting Antoni A arrangement. The spindle cells were characterized by flattened, elongated and tapered nuclei. Areas of hyalinized stroma were also seen depicting Verocay bodies. Presence of chronic inflammatory cells (lymphocytes and macrophages) and vascular channels was also seen. Neural bundles were evident at few areas in the stroma [Figure 3]. Immunohistochemical analysis using vimentin and S-100 markers revealed immunopositivity in both the immnoreactants [Figure 4]. Based on the clinicopathologic and immunohistochemical features, final diagnosis of a spindle cell lesion neurilemmoma was made. The patient was followed for a period of 15 days, 1, 3 and 6 months. No recurrence has been noted till date.
|Figure 3: Photomicrograph showing numerous fascicles of spindle cells with flattened, tapered nuclei. Areas of Antoni A arrangement of neural bundles and Verocay body-like areas are also seen|
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|Figure 4: IHC stained sections revealing immunopositivity with S-100 protein and vimentin|
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| Discussion|| |
In terms of their morphology, clinical associations and behavior, spindle cell tumors are among the most varied of human tumors, entailing an array of frequent misdiagnosis. The origin of these lesions may be attributed to epithelial, mesenchymal and odontogenic components pertaining to the oral cavity. It comprises of neural, myofibroblastic, muscle, fibroblastic, vascular, epithelial, odontogenic and miscellaneous tumors.
Neurilemmomas characteristically present as a globoid, encapsulated tumor associated with spinal or cranial sensory nerves. The etiological factor still remains suspicious, although it is thought to occur from spontaneous growth, external injury, chronic irritation or radiation. The foundation of the tumor pertains to frameshift mutations and deletions resulting in truncated protein concerning the NF2 gene at 22q12.2. It is a tumor suppressor gene coding for merlin (schwannomin), a cell membrane associated protein facilitating the linkage of the cell membrane and cytoskeleton, assisting in intracellular signaling pathways. The disease expression in NF2 correlates with the functional loss of the merlin (schwannomin) protein. In addition, SMARCB1/INI1 mutation has also been encountered in few cases.
The extracranial neurilemmoma most commonly presents in the head and neck region. Oral neurilemmomas usually occur in the soft tissue affecting the tongue, followed by palate, buccal mucosa, floor of the mouth, gingiva, vestibule, lips, salivary glands and the mental nerve region. It can develop at any age, but is more common in the 3rd and 4th decades, though it is also seen in children. They are typically slow-growing, solitary persistent tumors, having a definite female predilection. Despite neural origin, they usually are painless causing pressure on adjacent nerves rather than the nerve of origin and may present with paresthesia of the region of trigeminal sensory distribution. However, no such symptoms of paresthesia were observed in the present case.
The two clinical variants of the tumor exhibit as central and peripheral neurilemmoma, located in the bone and soft tissues, respectively. Although the soft tissue variant is the most frequently seen, intraosseous lesion accounts for only 1% of the central tumors with bony expansion. Intraosseous neurilemmomas are mostly seen in the posterior mandible and usually appear as either unilocular or multilocular radiolucencies on radiographs. Pain and paresthesia are not unusual for intrabony tumors. In the present case, the soft tissue lesion was accompanied by a radiolucent bony lesion with a thin radiopaque border in the left lower retromolar region. This possibly portrays that the periosteal lesion could have lead to secondary pressure erosion and penetration into the bone.
Microscopically, neurilemmomas are unilobular, well-encapsulated tumor masses with two histological patterns – Antoni A (hypercellularity) and Antoni B (hypocellularity). The first type is composed of spindle-shaped, flattened or fusiform cells with tapered or elongated nuclei arranged in a well-palisading manner and fascicles. Groups of fusiform nuclei and acellular eosinophilic masses, known as Verocay bodies, can be frequently seen in the tumor matrix. Antoni B type lesion shows a disorganized cellular arrangement in a loose fibrillary meshwork of cells along with microcysts, myxoid changes and inflammatory cells. In both patterns, the cytology of the individual cells is similar, with elongated cytoplasm and regular, oval nuclei. Degenerative changes can occur such as nuclear pleomorphism, xanthomatous change and vascular hyalinization.,, These features were found to be coherent with our present case. However, lack of necrosis, hyperchromatism and atypical features assisted in differentiating the lesion from other spindle cell tumors. Immunohistochemical analysis using S-100 protein, glial fibrillary acidic protein (GFAP), vimentin, etc., facilitates in the diagnosis and treatment planning of such intricate appearing lesions. Immunopositivity with S-100 and vimentin clearly indicates the lesion to be a spindle cell tumor with neural involvement in the above case.,
The prognosis of neurilemmoma is completely favorable, with conservative surgical treatment being the treatment of choice. If complete surgical enucleation with periodic follow-up is performed, recurrence is uncommonly observed. Malignant transformations are rare and still a contentious topic with difference in opinions among few authors. The anatomical uniqueness of the head and neck region renders this tumor to be structurally diverse and presence of twelve pairs of cranial nerves augment this exclusiveness. Neurilemmoma, despite its rarity, is one of the most understandable benign peripheral nerve sheath tumor, which may mimic a plethora of various other benign lesions. The present case further amplifies the importance of neurilemmoma and points toward the significance of the tumor in differential diagnosis of benign soft tissue tumors of the oral cavity.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]