Palatal malignant peripheral nerve sheath tumor: A case report and review of literature

Abstract

Malignant peripheral nerve sheath tumor (MPNST) is a rare, aggressive soft tissue malignancy associated with neurofibromatosis type 1. Although MPNST most commonly occurs in the extremities and trunk, it is rare in the head and neck region and extremely rare in the oral cavity, including the palate. MPNSTs arise from Schwann cells, de novo or from benign neural tumors. MPNSTs often occur between the ages of 30 and 50 years closely associated with neurofibromas. The median survival rate of the patients is 46-58% over ten years. Diagnosis is based on medical history and clinical examination, and treatment includes surgery, radiotherapy, and sometimes chemotherapy. Prognosis varies depending on location, size, and metastasis. We report an elderly female with a MPNST of the palate presenting with an exophytic lesion with details of clinicoradiographic and histopathologic features and long-term follow-up. This report describes a rare case of palatal MPNST and reviews the relevant literature.

Keywords

case report malignant peripheral nerve sheath tumor oral palate rare neoplasm

Introduction

Malignant peripheral nerve sheath tumor (MPNST), also known as neurofibrosarcoma, neurogenic sarcoma, or malignant schwannoma, is a soft tissue sarcoma with poor prognosis, aggressive behavior, limited therapeutic intervention,¹ and high recurrence rate in local regions.² MPNST is a rare malignant neoplasm that accounts for 5 to 10 percent of all soft tissue cancers and 0.001% of the incidence in the general population.³ Head and neck MPNST (HN-MPNST) accounts for 4% of all head and neck soft tissue sarcomas,⁴ HN-MPNST also represents 8-16% of all MPNST cases.^5,6 The most important etiologic factor for MPNST is the presence of neurofibromatosis type 1, as 50% of MPNST patients report a history of this disease.¹ The primary treatment for this disease is surgical excision.¹ Although MPNST can rarely occur in the head and neck region, most commonly involving the parotid gland, involvement of the oral cavity is extremely rare. In this article, we present a case of MPNST in the palate, an unusual location for this lesion.

Case report

An 80-year-old female with no history of systemic disease and no reported history of tobacco use, including smoking or chewing, was referred to an oral and maxillofacial surgeon around mid-2022. The patient noticed a swelling on the palate. Extraoral examination revealed no swelling or asymmetry in the facial area (Figure 1). Intraoral examination revealed an epiphytic, lobulated, sessile, ulcerated mass in the hard palate with a soft consistency (Figure 2).

Figure 1.

Clinical view, a female aged in her mid-80s with no swelling or asymmetry in the face.

Figure 2.

Intraoral view, showed a soft, lobulated, and sessile mass on the hard palate, exhibiting ulceration and epiphytic growth.

The patient was admitted to the Department of Oral and Maxillofacial Surgery in a hospital in another country. In 2022, she underwent surgery to remove a small palatal mass; the pathology report revealed undifferentiated sarcoma.

In 2023, the patient was referred to one of the hospitals of Tehran University of Medical Sciences, the Department of Oral and Maxillofacial Surgery, because of suffering from the recurrence of the lesion in the hard palate. A spiral neck computed tomography (CT) scan (with contrast) (Figure 3) showed a homogeneous mass approximately 30*13 mm in size in the right hard palate with mild bony remodeling and erosion in the underlying areas, with no obvious extension of the mass into the pharyngeal lumen or nasal cavity. The muscular structures had regular shapes and configurations. The vascular structures were intact with smooth walls. No significant cervical peripheral lymphadenopathy (LAP) is depicted; both thyroid lobules were normal in size and shape.

Figure 3.

CT-scan, a uniform mass located in the right hard palate, exhibiting mild bony remodeling and erosion in the adjacent area, without any noticeable extension.

A spiral chest CT scan (with contrast) revealed an ill-defined right hilar soft tissue with obliteration of the right middle pulmonary artery. There were some irregularly bordered nodular lesions of varying size (up to 19 mm) at the Right Middle Lobe (RML) and Right Lower Lobe (RLL). Passive segmental collapse was noted in the upper segment of the RLL and in the medial segment of the RML. Some calcified left hilar lymph nodes with some large pericardiophrenic LAPs (SAD=12mm) were also present. Some centriacinar ground glass nodules were also seen in the RML, which could indicate active infections. No pleural effusion was noted. The differential diagnosis was an old TB infection and a neoplastic process. The size of the large cardiac vessels was within normal limits. No definitive evidence of metastatic disease was identified, and pulmonary findings were considered indeterminate.

The previous slides and paraffin blocks were not available for rechecking because of the migration of the patient. An incisional biopsy was performed; the macroscopic features were ‘two dome-shaped white cream-colored solid tissues covered by ulcerated mucosa, measuring totally 1.6 * 0.8 * 0.5 cm, the section showing a non-homogeneous solid white soft surface. The microscopic features showed a malignant hypercellular mesenchymal neoplasm consisting of ovoid to spindle-shaped cells proliferating in long and short interlocking fascicles and storiform patterns in a hypo- to hyper-cellular manner in scant myxoid to fibrotic stroma. Significant atypia and numerous atypical mitotic figures were evident (Figure 4(a) and (b)). The superficial parakeratotic stratified squamous epithelium of the oral mucosa was invaded and ulcerated by the tumor cells. Regional mucinous minor salivary glands acini were affected by tumor cells. There were various differential diagnosis consisting of poorly differentiated carcinoma, melanoma, leiomyosarcoma, malignant peripheral nerve sheath tumor, and other sarcomas. Immunohistochemical (IHC) analysis demonstrated negativity for pan-cytokeratin (PanCK), HMB45, and desmin, thereby excluding poorly differentiated carcinoma, malignant melanoma, and leiomyosarcoma, respectively. α-SMA positivity was confined to stromal vessels. Strong tumoral expression of vimentin (diffuse) and S-100 (scattered) supported the diagnosis of malignant peripheral nerve sheath tumor. Tumor cells demonstrated scattered CD34 positivity, and the Ki-67 labeling index was approximately 70%, indicating a high proliferative activity. (Figure 4(c)–(f)). The final diagnosis was a high-grade malignant spindle cell neoplasm with IHC features consistent with malignant peripheral nerve sheath tumor.

Figure 4.

Microscopic view, (a) proliferation of spindle cells with mild atypia (magnification ×100); (b) proliferation of spindle cells with prominent nuclear atypia and scattered atypical mitotic figures (magnification ×400); (c) strong positive immunostaining in tumoral cells in vimentin (magnification ×200); (d) areas of positive immunostaining for S-100 in tumoral cells (magnification ×200); (e) background vessels showed positive staining for α-SMA (magnification ×200); (f) Ki67 showed proliferation activity in about 70% of the tumoral cells (magnification ×200).

About two months after the recurrence, surgical removal of the lesion with safe margins was performed as the main treatment for the patient (Figure 5). Final microscopic evaluation of the lesion confirmed the initial diagnosis of MPNST. Now, after 3 years, the patient is alive and has no signs of recurrence or distant metastasis. Consent form for treatment and also publishing was obtained from the patient, and all patient details have been de-identified.

Figure 5.

Removed mass with a safe margin.

Method

This case report conforms to the CARE guideline.⁷ The search was performed in PubMed, Google Scholar, and Scopus, which retrieved twenty-one cases (Table 1) consisting of 18 MPNST cases and 3 cases of malignant Triton tumor (case numbers 19 to 21, Table 1) from 1988 to 2023.

Table 1.

Conducted in 2025, tumor locations data extracted from articles’ texts or figures, all sizes are in cm and shows tumor in its biggest dimension in clinical examinations.

NO	Author(year)	Age	Tumor location	Immunohistochemistry	Clinical features	Recurrence	Treatment
NO	SEX	NF1	Tumor size (cm)	Systemic history	Country	Metastasis	Follow-up
1	Bartier⁸(2023)	62	RHP + Right cheek	H3K27me3(-ve), p16(-ve), SMA(+ve), MDM2(+ve), cytokeratins(-ve), p40(-ve), desmin(-ve), S100(-ve), SOX10(-ve), ALK1(-ve), MUC4(-ve), Ki67(10%)	Swelling	NO	Total maxillectomy + Resection of Orbital floor + Radiotherapy(60 GY)
1	Female	NA	4.3(MRI)	hypertension + smoking	France	NO	After 24 months- well situation
2	Suryawanshi⁹(2023)	52	RHP + Right cheek	S-100(+ve), SOX-1(+ve)	Swelling, Loss of sensations, watery nasal discharge, Pain, headache	NA	NA
2	Female	NA	NA	NA	India	NA	NA
3	Li¹⁰(2023)	62	AntP	S100(+ve), SOX10(+ve), nestin(+ve), partial loss of H3K27me3, HMB45(-ve), Ki-67(+ve, rate10%)	pigmented, asymptomatic, swelling	YES	partial maxillectomy + radical neck dissection
3	Female	NO	NA	NA	China	YES	After 24 months - lung and bone metastases
4	Oh¹¹(2022)	38	LHP	S100(+ve), Desmin(-ve), Ki67(+ve)	tooth pain, tooth extraction cause of pain	NA	Partial maxillectomy + adjuvant radiotherapy
4	Female	NO	NA	No particular illness	Korea	YES	Metastasis after 3 month - patient died after 22 months
5	Arruda¹²(2016)	16	LHP	S-100(+ve), GFAP(+ve)	pain and endodontic treatment of tooth, chromatic alterations, mobility	NO	Surgical excision of tooth + CSE of lesion + Chemotherapy
5	Female	NO	2.5	NA	Brazil	NO	After 108 months - tumor free
6	D'Addino¹³(2016)	78	right cheek ext to RHP	Vimentin(+ve), S100(+ve), AE1–AE3(-ve), AM1(-ve)	At first asymptomatic, hypoesthesia, ulceration, bleeding	NO	CSE AND chemotherapy
6	Male	NO	10	hypertension + smoking + chronic atrial fibrillation + type 2 diabetes + diabetic neuropathy + and microangiopathy	Argentina	cannonball metastases	Died 18 months after surgery
7	Tamgadge¹⁴(2014)	65	Distal of left maxilla ext to palate	S100(+ve)	swelling, numbness,discomfort in mastication, pain, firm, no tenderness	NA	NA
7	Male	NO	5	No particular illness	India	NA	NA
8	Sahai¹⁵(2014)	38	Left cheek ext to HP	S100(+ve), Vimentin(+ve), Cytokeratin(-ve), epithelial membrane antigen(-ve), desmin(-ve), myogenin(-ve), SMA(-ve), MIC-2(-ve), BCL-2(-ve), CD34(-ve), CD99(-ve)	Pain, bleeding, swelling, ulcer	YES	Total left maxillectomy + Radiotherapy + Chemotherapy
8	Male	NO	8	use of tobacco	India	NO	After 5 months - died
9	Ali¹⁶(2011)	50	Right maxilla ext to pterygopalatine fossa	Cytokeratines(-ve), actin(-ve), desmin(-ve), myoglobin(-ve), factor VIII(-ve), S-100(+ve)	swelling, asymptimatic, firm, no ulceration	NO	hemimaxillectomy + Adj radiation
9	Male	NO	6	No particular illness+ tobacco chewing and smoking	Pakistan	NO	After 8 months - well condition
10	Janardhanan¹⁷(2011)	40	PP + right buccal region of maxilla	S100(-ve)	swelling, dull aching pain	YES	Radiotherapy
10	Male	YES	5	several cutaneous nodules from child age	India	YES	After 2 months - died
11	Che¹⁸(2006)	13	RHP (canine and icisors region)	S100(+ve)	noticing in dental treatment, recession of gingival, mobile tooth, external resorption of tooth	NO	Transoral wide excision + anterior maxillectomy
11	Female	NO	NA	NA	Korea	NO	Well condition in following
12	Bagan¹⁹(2005)	12	RHP (canin regoin)	Cytokeratines(-ve), Actin(-ve), Desmin(-ve), Myoglobin(-ve), Factor VIII(-ve), Vimentin(+ve), S100(+ve)	pain, mobile teeth	YES	Hemimaxillectomy + Radiotherapy
12	Male	NO	3	pneumonia, occasional cephaleas	Spain	NO	10 months after surgery - died
13	Neetha²⁰(2004)	12	Left cheek extended to palate	NA	swelling, firm	NA	CSE
13	Female	NA	NA	NA	India	NA	NA
14	Muraki²¹(1999)	43	HP	Vimentin(+ve), S100(+ve), p53(+ve),Desmin(-ve), p21ras(-ve)	swelling, with pain	YES	Tumorectomy + right maxillectomy + chemotherapy
14	Male	YES	NA	cutaneous neurofibromas	Japan	NO	20 months after first operation - died from extension to skull
15	Nagayama²²(1993)	60	right anterior antral wall with extension to palate	S100(+ve), Vimentin(+ve), Cytokeratin(-ve), Desmin(-ve), GFAP(-ve)	swelling, numbness	NO	neo-adjuvant chemotherapy + radiation then right total maxillectomy + orbital exenteration
15	Male	NO	NA	No particular illness	Japan	NO	Chemotherapy and radiation effects were poor - 3 years after surgery patient had well condition
16	DiCerbo²³(1992)	13	LHP	NA	Tender	YES	HPY
16	Female	NA	1.5	asthma + smoking + drink alcohol	USA	NO	After 84 months - well condition
17	Gratz²⁴(1991)	79	LHP	PAS(-ve), S100(+ve), Vimentin(+ve), Desmin(-ve), factor VIII(-ve), keratin(-ve), alpha-l-antitrypsin(-ve), alpha-l-antichymotrypsin(-ve)	No pain, swelling, with ulceration	YES	PRM + FNA + RND
17	Male	NA	NA	NA	Switzerland	YES	After 48 months - pulmonary and liver metastasis been seen
18	Urade²⁵(1990)	47	Left maxilla	NA	bleeding, swelling	YES	CSE + Adj radiation and chemotherapy
18	Female	NA	NA	NA	Japan	YES	After 22 months malignant melanoma appeared - died after 31 months
19	Elleuch²⁶(2018)	23	Left maxilla	S100(+ve), Keratin(+ve), desmin AND MyoD1 AND myogenin (+ve in rhabdomyoblastic cells)	swelling, with pain, with ulceration, bleeding	YES	Chemotherapy + hemimaxillectomy + radiotherapy
19	Female	NO	NA	No particular illness	Tunisie	NA	2 months after chemotherapy and hemimaxillectomy noticed recurrence
20	Can²⁷(1999)	30	Right maxilla	S100(+ve), Desmin(+ve), Myoglobin(+ve)	extraction of tooth and postoperative swelling in the tumor region (chronic inflamatory process), ulcerated	NO	Total maxillectomy + radiotherapy
20	Female	NO	8	Von recklinghausen disease	Turkey	NO	After 24 months - well condition
21	Shotton²⁸(1988)	28	LHP	S100(+ve), Desmin(+ve)	ulcer, extraction of tooth in the tumor site cause of pain	YES	chemotherapy + radiotherapy + Surgery
21	Female	NA	6	NA	UK	YES	After 22 months of initial presentation - patient died
22	Karimi [this case] (2026)	86	HP	PanCK(-ve), HMB45(-ve), desmin(-ve), α-SMA(-ve in tumor cells/+ve stromal vessels), vimentin(+ve), S-100(+ve), CD34(+ve), Ki-67(∼70%)	Swelling	YES	surgical removal of the lesion
22	Female	NO	(CT scan): 30 × 13 mm	No particular illness	Iran	NO	After 3 years - well condition

RHP: Right hard palate, +ve: positive, -ve: negative, AntP: Anterior of the palate, LHP: Left hard palate, CSE: Complete surgical excision, ext: extended, PP: Posterior palate, HP: Hard Palate, HPY: hard palatectomy, PRM: Partial resection of the maxilla, FNA: Fine needle aspiration, RND: Radical neck dissection, SMA: Smooth Muscle Actin, ALK: Anaplastic lymphoma kinase.

Literature review

Two of the cases had neurofibromatosis type 1, and both showed cutaneous signs such as nodules. Follow-ups of these patients revealed that they died of the disease. The youngest and oldest reported patients were 13 and 79 years old, respectively.

The palate may also be the primary site of the tumor, or it may spread to the palatal region. The most common primary sites that may be involved were the palate and the cheeks. S100 was always one of the targets in IHC testing showing positive immunoreaction in all cases except one.

Based on the reviewed reports, dentists and oral hygienists were an important part of the healthcare system to recognize and refer these patients early.

Discussion

Malignant peripheral nerve sheath tumor can arise as a malignant transformation of a benign nerve sheath tumor or de novo from a peripheral nerve.²⁹ This lesion has an overall survival rate of 46-58% in 10 years.³⁰ MPNST is strongly associated with neurofibromatosis type 1 (NF1), and patients with internal plexiform neurofibroma have an approximately 20-fold increased risk of developing this malignancy.³¹ Etiologically, MPNSTs can be divided into these three types: 1- sporadic, 2- neurofibromatosis type 1 (NF1), and 3- due to radiotherapy,³² with the last type having the rarest rate and a poorer prognosis.³³

MPNSTs most commonly occur in the extremities (arms, legs, and most commonly sciatic nerve),³⁴ whereas involvement of the head and neck region (HN-MPNST) is uncommon. In HN-MPNST, the first tumor signs occur in the autonomic and peripheral nerves in 46% of all cases, in the connective/soft tissue regions in 31.5%, and in the nasal and paranasal areas in 9.6%. The mean age of HN-MPNST is higher than that of MPNSTs occurring in other parts of the body (49 YO – 46 YO, respectively), but there is no significant difference in the mean survival rate between these two groups. In terms of sex predilection, HN-MPNST is more likely to occur in males (60%) than MPNST in other sites (45%).³⁵ MPNST in the paranasal sinuses and hard palate is also reported very rare.⁸ In contrast to typical head and neck MPNST patterns, the present case involves an elderly female patient with tumor involvement of the hard palate, an exceedingly rare site for this entity.

As with any peripheral nerve tumor (PNT), a complete history and clinical examination are the most important sources of information for diagnosis. Physical features may include soft tissue mass, pain, and loss of sensation. Unlike benign peripheral nerve tumors, MPNSTs have a progressive neurological deficit and a rapid growth rate.³⁶ Zhou et al. noted the loss of sensation, pain, a soft tissue mass, and laxity at the tumor site (in the reported case, the hand) are symptoms, but none of these features can determine the type of nerve tumor. Typically, PNTs move vertically to the nerve axis, but they are fixed on the axis of the nerve.³⁷

In radiographic evaluation it is common to see some features including edema around the lesion, cystic necrosis, and disorganized margins. Lesion size cannot differentiate benign from malignant types alone. Radiologic findings are usually supportive rather than diagnostic.³⁸ A previously reported case showed a well-defined, lobulated lesion with relative T1 hyperintensity and T2 hypointensity on MRI.³⁹ Our reported case was assessed by CT, demonstrating a homogeneous palatal mass with mild bony remodeling.

Histologically, MPNST is characterized by hypercellular spindle cell proliferation with numerous atypical mitotic figures and prominent cellular atypia, pleomorphism, and increased N/C ratio.⁴⁰ In some variants, it may show heterogeneous elements, including skeletal muscle differentiation, cartilage, bone, or glandular structures; marbling may also be seen.²⁹ Rhabdomyoblastic differentiation may also be associated with a poor prognosis, but NF1 status does not affect.⁴¹ IHC markers are mainly S100 and SOX10, but even they are limited in their ability to show MPNST.⁴² Some studies suggest that these two markers can be seen in 50% of MPNSTs²⁹; other markers are p16, p75NTR, p53, neurofibromin, and EGFR.⁴² In 2019, Senthilkumar et al. reported a case of MPNST using S100 and Ki67. Both markers were strongly positive (S100 in 95% of tumor cells and Ki67 in 10-15% of tumor cells).⁴³ S100 and SOX10 lack specificity for neural origin and may be expressed in other spindle cell sarcomas; therefore, a broad immunohistochemical panel is essential to exclude alternative malignancies, such as malignant melanoma or rhabdomyosarcoma. In the present case histopathological reported features of MPNST, including spindle cell morphology and S-100 positivity were observed. However, despite a markedly high Ki-67 labeling index (approximately 70%), the clinical outcome was favorable, contrasting with the poor prognosis commonly described in the literature.

MPNSTs that occur in the trunk have a worse prognosis than hands and feet.^44,45 However, it is said that NF1 does not influence the prognosis and is not associated with poor prognosis in some articles.⁴¹ On the other hand, in some other studies it plays a significant role in a poor prognosis, do its size, location, metastasis and grading.⁴⁶ Usually, surgery is the primary treatment, but the type of surgery may vary from case to case; patients may need aggressive or conservative surgery, and adjuvant radiotherapy with a dose of ≥ 60 Gy can control the tumor locally.^47,48 Chemotherapy is usually accepted for metastatic cases.⁴⁹ Kaplan reported a case of MPNST in 2013 in which vemurafenib was presented as a beneficial systemic treatment for this lesion.⁵⁰ In our case, after consultation with the oncologist, adjuvant chemotherapy was not required for the patient because of free margins. A limitation of this case report is the absence of serial surveillance imaging during follow-up, due to the patient’s migrant status and difficulty visiting the surgeon and undergoing clinical examination. Therefore, long-term follow-up and the patient assessment were primarily based on calling and self-assessment.

Conclusion

MPNST is a rare soft tissue tumor that can occur in all parts of the body, but it is less common in the head and neck region. Malignant peripheral nerve sheath tumors have a difficult diagnosis and require clinical, histologic, and radiologic evaluations. Surgery and adjuvant radiotherapy are commonly used for local situation control. In this report, we present a patient suffering from MPNST in the hard palate. The tumor was diagnosed based on accurate physical examinations, radiographic patterns, histopathological features, and immunohistochemical findings. The patient underwent surgery, and fortunately after 3 years of follow-up, there is no evidence of recurrence.

Footnotes

ORCID iD

Seyed Mohammadmoein Hosseini

Ethical considerations

This study was approved by the Ethics Committee of BY Research Ethic committees of school of dentistry – Tehran University of Medical Sciences (IR.TUMS.DENTISTRY.REC.1404.095).

Consent to participate

Written informed consent obtained from the patient.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data Availability Statement

The data underlying this article cannot be shared publicly to protect patient privacy. Data are available from the corresponding author upon reasonable request.*

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