|Year : 2016 | Volume
| Issue : 1 | Page : 49-52
Intramandibular malignant peripheral nerve sheath tumor: A case report
Bhavana S Bagalad, Anuradha Ananthaneni, Vijay Srinivas Guduru, Puneeth Horatti Kuberappa
Department of Oral Pathology and Microbiology, St. Joesph Dental College, Eluru, Andhra Pradesh, India
|Date of Web Publication||18-Jan-2016|
Bhavana S Bagalad
Department of Oral Pathology and Microbiology, St. Joesph Dental College, Room No. 6, Eluru - 534 004, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
The principal malignancy of peripheral nerves is malignant peripheral nerve sheath tumor (MPNST), which is common in soft tissue of the lower extremities. Its occurrence in the head and neck region is about 10-20%, which makes it a rare entity. Intraosseous MPNST is rare in the literature. Here, we discuss the case report of de novo occurrence of MPNST in the mandible of a 25-year-old female patient.
Keywords: Neurofibrosarcoma, schwannoma, S-100
|How to cite this article:|
Bagalad BS, Ananthaneni A, Guduru VS, Kuberappa PH. Intramandibular malignant peripheral nerve sheath tumor: A case report. Saudi J Oral Sci 2016;3:49-52
|How to cite this URL:|
Bagalad BS, Ananthaneni A, Guduru VS, Kuberappa PH. Intramandibular malignant peripheral nerve sheath tumor: A case report. Saudi J Oral Sci [serial online] 2016 [cited 2020 Aug 8];3:49-52. Available from: http://www.saudijos.org/text.asp?2016/3/1/49/174337
| Introduction|| |
Schwannoma is a rare intraoral benign connective tissue tumor derived from Schwann cells associated with nerve sheath of peripheral nerves.  The term malignant peripheral nerve sheath tumor (MPNST) replaces the former terms malignant schwannoma, neurofibrosarcoma, and neurogenic sarcoma because MPNSTs recapitulate the appearance of various cells of the nerve sheath, with tumors ranging from neurofibroma to those resembling a fibrosarcoma.  Intraosseous MPNSTs are unusual and very rare in the literature.  The diagnosis of MPNST is complicated because of the unclear criteria for its determination. We reported a case of intraosseous MPNST of the mandible of a 25-year-old female patient, which was clinically diagnosed as an odontogenic cyst but at histological examination turned out to be MPNST.
| Case Report|| |
A 25-year-old female patient complained of swelling in the left lower third of the face present since 5 months with no history of pain. History revealed that the swelling started as a small one extending from the premolar to the molar with no considerable change in the size over time with spontaneous exfoliation of 35, 36, and 37.
Extraoral examination revealed facial asymmetry with diffuse swelling of about 2 × 2 cm, extending anteroposteriorly 1 cm away from the corner of the mouth to 1 cm anterior to the angle of the mandible. Superoinferiorly, it extended 0.5 cm below the ala-tragus line till the lower border of the mandible. On palpation, the swelling was nontender and hard in consistency with no local rise of temperature.
Intraorally, the swelling extended from 35 to 37 with indistinct borders and obliterating the vestibule [Figure 1]a. Buccal cortical expansion was distinct. Mucosa over the swelling was pale yellow in color. Swelling was slightly tender, nonmobile and stony hard in consistency.
|Figure 1: (a) Photomicrograph showing unhealed socket of exfoliated teeth (36, 37) covered by debris with vestibular obliteration (b) Photomicrograph of orthopantomogram (OPG) showing well-circumscribed unilocular radiolucency with sclerotic borders extending from the distal aspect of 35 to the mesial aspect of 38|
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Panoramic radiograph revealed unilocular radiolucency with a sclerotic border extending from the distal aspect of 35 to the mesial root of 38 [Figure 1]b. Based on the clinical and radiographic features, differential diagnoses of keratocystic odontogenic tumor (KCOT) and unicystic ameloblastoma were made.
Under local anesthesia, intraoral, deep incisional biopsy was performed with respect to the edentulous area of 35, 36, and 37. Histopathology showed fibrocellular connective tissue stroma with bland hypercellular areas consisting of elongated spindle-shaped cells with indistinct cell borders containing a flattened nucleus with rounded edges arranged haphazardly. Based on these features, a diagnosis of benign spindle cell tumor was made and the patient's consent for immunohistochemistry (IHC) staining was obtained. Following the biopsy, unsatisfactory wound healing was observed. The patient wanted the lesion to be excised at the earliest and thereby, excisional biopsy was performed under general anesthesia. Histopathological examination showed dysplastic spindle-shaped cells arranged in fascicles with dense cellular areas alternating with the hypocellular areas [Figure 2]a with the focal area demonstrating palisading of nuclei [Figure 2]b. Heterologous elements such as the bone [Figure 3]a were also evident with perivascular invasion [Figure 3]b. A differential diagnosis of leiomyosarcoma and MPNST was arrived at to make a definitive diagnosis; IHC was performed with S-100, along with Masson's trichrome stain. The tumor cells showed positivity for S-100 [Figure 4]a and negativity for Masson's trichrome stain [Figure 4]b. These features were suggestive of MPNST.
|Figure 2: (a) Photomicrograph showing spindle cells with dysplastic and alternating areas of hypocellular and hypercellular spindle cells in the background of fibrous stroma [H and E, 20×] (b) Photomicrograph showing areas of schwannoma [H and E, 20×]|
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|Figure 3: (a) Photomicrograph showing heterologous bone [H and E, 10x] (b) Photomicrograph showing perivascular invasion of tumor cells [H and E, 20x]|
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|Figure 4: (a) Photomicrograph showing S-100 positivity of tumor cells [IHC, 10x] (b) Photomicrograph showing no evidence of muscle in Masson's trichrome stain [10×]|
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| Discussion|| |
The World Health Organization (WHO) defined MPNSTs as a subcategory of soft tissue sarcomas arising from a peripheral nerve or showing a nerve sheath differentiation, with the exception of tumors originating from the epineurium or the peripheral nerve vasculature. 
The most probable origin of neurogenic tumors is Schwann cells; however, perineural and endoneural fibroblasts can contribute at times. MPNST is the only single type of recognized malignant neurogenic tumor. MPNST can also arise de novo, as the present one. Few cases are secondary to radiation exposure and neurofibromatosis. 
Etiology for MPNST is thought to be multistep and multigene process with loss of chromosome arm 17q sequence including complete inactivation of neurofibromatosis-1 gene. This tumor occurs commonly between the second decade and the fifth decade with equal sex predilection.  It is in accordance with our case, which was in a 25-year-old female patient.
Head and neck involvement is seen only in 8-16% of the cases, mainly the parotid gland or the infratemporal fossa.  MPNST arising in the mandible is very infrequent, and to our knowledge about 22 cases are reported in the jaws, 13 in the mandible, and 9 in the maxilla  and probably this is the 14th case of intraosseous MPNST in the mandible. Intraosseous MPNST may arise from a nerve passing through a bony foramen or may be due to the secondary erosion of the bone by the extraosseous one. Moreover, their periapical involvement and predominant jaw localization suggest the possibility of an odontogenic neuroectodermal origin. However, this requires more supportive evidence. 
Earlier, it was believed that to make a diagnosis of MPNST, one must demonstrate any of the following:
- Origin from the nerve or from the preexisting benign nerve sheath tumor.
- Ultrastructural evidence of Schwann cell differentiation.
- Development of spindle cell sarcoma in a patient with neurofibromatosis type 1.
However, over a period of time it has become apparent that MPNST shares reproducible morphologic features, which can be sufficient to enable their recognition, especially if supported immunohistochemically. 
Clinically, it tends to grow slowly, as seen in this case but sometimes may exhibit rapid growth.  Probably because of this slow growth in the present case, despite being a malignant lesion it radiographically showed a sclerotic border. When associated with major nerve trunks, projecting pain, paresthesia, and weakness are the common symptoms.  This tumor can metastasize by hematogenous and perineural spreads. Rarely, is lymph node metastasis noted.  In the present case, though histopathologically perivascular invasion was seen, clinically lymph node metastasis was not evident.
MPNST characteristically shows dense and hypodense fascicles alternating in a marble-like pattern consisting of asymmetrically tapered spindle cells with irregular buckled nuclei.  Few display a peculiar nodular, curlicue, or whorled arrangement of spindle cells. Spindle cells consist of hyperchromatic elongated nuclei and abundant cytoplasm. The majority of tumors show localized necrosis. MPNSTs vary from low grade lesions to the more common high grade tumors, which have brisk mitotic activity.  Approximately, 20% of the cases show focal divergent differentiation toward mesenchymal diseases such as rhabdomyosarcoma, chondrosarcoma, osteosarcoma, angiosarcoma, and liposarcoma or toward glandular and squamous type epithelial tumors. The explanation for this wide range of neoplastic phenotypes is that cells of the neural crest also contribute to the formation of leptomeninges, bone, cartilage, and muscle in the head, neck, and face. Secondary features of MPNST include myxoid change, hyalinization, and geographic necrosis. 
Differential diagnosis includes leiomyosarcoma, fibrosarcoma, and monophasic synovial sarcoma. MPSNT should be differentiated from these lesions by characteristic histological features, special stains, and IHC. ,
IHC plays a crucial role in the diagnosis of MPNST. The most widely used antigen, S-100 protein is known to be positive in 50-90% of MPNST cases. Leu-7 and myelin basic protein are found in 50% and 40% of them, respectively. Recent studies suggest that nestin, the intermediate filament protein, is more sensitive for MPNST than other neural markers.  In the present case, lesional tissue showed positivity for S-100.
Treatment and prognosis
MPNST is highly aggressive and has a high propensity to metastasize to distant sites. The important prognostic factors are large tumor size (>5 cm), presence of neurofibromatosis, and positive margin.  Therefore, its management requires a block resection and sometimes even radiation therapy has been recommended.  The present case also showed the typical ill-defined margin of MPNST, with an eroding pattern. To prevent the local recurrence, adjuvant radiotherapy must be given in cases with postoperative positive margins, thereby suggesting that MPNST has a distinctly worse prognosis than other soft tissue sarcomas. 
| Conclusion|| |
Intraosseous MPNST is very rare. In the present case, de novo origin of aggressive MPNST was suspected. Even though there has been substantial progress in the management, the widespread nature of MPNST puts a hold on its prognosis. Early detection can help to reduce mortality.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]