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Malignant peripheral nerve sheath tumor of the infratemporal fossa with intracranial extension.


Malignant peripheral nerve sheath tumor (MPNST) is an uncommon neoplasm that rarely involves the head and neck region. We report the case of a 66-year-old man who presented with symptoms compatible with uncinate seizures. Imaging studies detected a left infratemporal fossa tumor with bone tissue destruction and extension into the intracranial compartment, which exerted a mass effect on the temporal lobe. Histologic studies identified the tumor as an MPNST. Complete removal of the lesion was not possible, so the patient was treated with adjuvant radiotherapy. He died 6 months later. This rare case of MPNST with intracranial involvement illustrates the dismal prognosis for patients with such a lesion. Survival is limited because of the difficulty of performing radical surgery with free margins in such a location.


Malignant peripheral nerve sheath tumor (MPNST) was previouslyknown as malignant schwannoma, neurogenic sarcoma, malignant neurilemmoma, and neurofibrosarcoma. MPNST is a rare neoplasm that originates in nerve sheath cells, including Schwann cells and neural and perineural fibroblasts. (1) It accounts for about 5 to 10% of all soft-tissue sarcomas, and its prevalence among the general population is around 1 per 100,000. (2, 3) The presence of an MPNST in the head and neck and involvement of the central nervous system are very uncommon. (2, 4-10) We report a case of an infratemporal fossa MPNST with extension into the intracranial compartment.

Case report

Our patient was a 66-year-old man who arrived at our emergency department with symptoms compatible with uncinate seizures along with headache and memory loss. Computed tomography (CT) and magnetic resonance imaging (MRI) (figure 1) detected a lesion in the left infratemporal fossa with extension into the intracranial compartment and destruction of bone tissue in the lateral orbit wall, the sphenoid sinus, and the anterior part of the petrous bone. The tumor also produced a mass effect over the pole of the temporal lobe. With intravenous contrast administration, the lesion enhanced brightly. Thoracoabdominal CT did not demonstrate any other lesions.

The patient underwent surgery, which involved a left temporal craniotomy with zygomatic arch osteotomy and an almost complete tumor removal (figure 2). A small amount of residual tumor had to be left because the consistency of the tumor made it very hard to dissect it from delicate structures such as the cavernous sinus (figure 3).

On gross inspection, the mass had a very fibrous and hard consistency. Histologic study identified a malignant proliferation of spindle-shaped cells arranged in short, parallel bundles with alveolar pattern areas and occasional mitoses. The Ki-67 index was approximately 10%, and immunohistochemical studies showed focal positivity for S-100 protein, an absence of epithelial membrane antigen (EMA), and an absence of expression of markers for striated muscle.

The patient tolerated the surgery well, and immediately experienced clinical improvement, with the disappearance of both the uncinate seizures and the headache in addition to subjective improvement in memory. Adjuvant treatment with 60 Gy of linear accelerator radiotherapy was planned, but after the patient had received a total of 36 Gy, he began to progressively deteriorate and experience cognitive impairment and lethargy.

Repeat CT detected signs that the intracranial tumor had progressed and that it was exerting a mass effect on the brainstem. Treatment was stopped, and the patient died 6 months postoperatively. Chemotherapy was not considered because of the rapid worsening of the patient's condition and the absence of systemic disease.



The histologic findings and behavior of the lesion in our patient were consistent with those of previously described cases of MPNST in the literature. The location of an MPNST in the infratemporal fossa and its extension into the middle cranial fossa is very uncommon, as fewer than 50 cases of a maxillomandibular site have been reported in the literature. (7) The most common locations for this type of tumor are the extremities and the trunk; head and neck involvement is seen in about 10% of cases. (2, 3, 8, 10, 11)


These lesions are usually diagnosed in patients aged 20 to 50 years; cases in children and the elderly have also been reported. (2) There is a known association between MPNST and neurofibromatosis type 1 (NF- 1). MPNSTs have been reported to develop in 2 to 29% of NF-1 patients, typically in younger patients. (2, 10, 12) The lifetime risk of MPNST is approximately 4,600 times greater in NF-1 patients than in those without. (2, 10, 12) In patients without NF-1, MPNSTs usually develop de novo; in NF- 1 patients, they develop more often as a malignant progression of preexisting plexiform neurofibroma.

MPNSTs are very aggressive neoplasms, with 5- and 10-year survival rates ranging from 30 to 50% and 20 to 30%, respectively. The most important prognostic factors are the extent of resection, tumor size, and tumor location. Some studies have suggested that the prognosis is worse in patients with NF- 1, as they have a tendency toward larger lesions, poorer differentiation, multifocality, and higher rates of metastasis. (2, 10, 13) These findings, however, were not confirmed in other series. (5, 14)


Most of the deaths attributable to MPNST are caused by local progression, local recurrence, or systemic dissemination. Relapse occurs in more than 50% of patients after treatment (local recurrence in 45 to 60%, and metastasis in 16 to 40%); this rate is among the highest recurrence rates of all the sarcomas. (4, 5, 7) MPNSTs spread hematogenously, and lung metastases are common. Extension along the nerve sheath to considerable distances has also been described. Cases of lymphatic spread are very rare. (15, 16)

The diagnosis of MPNST is difficult. It is based on a combination of gross, histopathologic, and immunohistochemical findings. The histologic findings are quite variable. The typical tumor consists of spindle cells arranged in a fascicular or herring-bone pattern, similar to a fibrosarcoma, with some hypocellular myxoid zones and various degrees of mitosis, necrosis, and tumor calcification. Foci of divergent differentiation are not uncommon, with rhabdomyosarcomatous, osteosarcomatous, chondrosarcomatous, and angiosarcomatous elements appearing in some cases. These characteristics make it difficult to distinguish MPNSTs from other spindle cell sarcomas such as fibrosarcoma, leiomyosarcoma, monophasic synovial sarcoma, etc. Sometimes an associated benign neurofibroma or Schwann cells are seen. (1, 2, 4, 10) It has been reported that the nerve of origin could not be detected surgically in as many as 60% of patients, although this is not necessary in order to make the diagnosis; in such cases, the lesion is presumed to originate in small, insignificant nerves such as those from perivascular plexuses. (2, 10, 12) Because the histology is not very specific, immunohistochemistry plays a major role in the diagnosis. The most important immunohistochemical finding is the presence of focal positivity for S-100 protein, which is seen in as many as 75% of cases.17 S-100 positivity is not seen in other spindle cell sarcomas. Also, some cases of MPNST stain positive for neuron-specific enolase. Staining for cytokeratins and EMA reactivity is usually negative. Electron microscopy can be very useful in differentiating MPNST from other lesions; findings such as interdigitating processes, focal basal lamina, and scanty intercellular junctions direct us to a Schwann cell origin. (4, 15)

The most widely known grading systems used to classify MPNSTs are the soft-tissue sarcomas systems developed by the U.S. National Cancer Institute and the French Federation Nationale des Centres de Lutte Contre le Cancer. (18-20) In these systems, tumors are classified into one of three grades based on tumor differentiation, necrosis, and mitotic activity. Their prognostic value has not been demonstrated for MPNSTs. Some studies did not find any correlation between tumor grade and survival, (2, 10, 14) while others did demonstrate statistically significant relationships in all patients with MPNST (5) and in non-NF1 patients only. (21)

Treatment of these aggressive neoplasms is not standardized. The most widely accepted treatment is radical excision with free margins when possible. (2, 10, 22) This is sometimes not feasible because of the size or location of the tumor, especially in head and neck cases, which may explain the poor prognosis among these patients. The role of adjuvant therapy is not clear. Neither radiotherapy nor chemotherapy has consistently been shown to increase survival rates, although postoperative radiotherapy is widely used to control local recurrences. Chemotherapy is usually reserved for patients who experience a systemic relapse, and multiple regimens have been used. (2, 10, 22-25) Chemotherapeutic regimens that include ifosfamide seem to produce better results, even allowing for delayed surgery (i.e., postchemotherapy) for some patients whose lesions had been previously considered unresectable. (23)

Our report describes a rare case of infratemporal fossa MPNST with intracranial extension. We believe the tumor in our patient originated in the third branch of the trigeminal nerve, with extension into the middle fossa through the foramen ovale. Trigeminal nerve MPNSTs are not usually related to neurofibromatosis; instead, they appear as de novo lesions, with the most common symptom being facial numbness. (15) The uncinate seizures that our patient experienced are believed to have been caused by the tumor's mass effect on the temporal lobe; the patient presented with no symptoms secondary to nerve dysfunction, a fact that delayed the diagnosis. Radical surgery with total excision was not possible, and this probably explains the patient's short postoperative survival. This case illustrates the importance of early diagnosis of MPNSTs, especially those in the head and neck region, because radical excision with free margins seems to be the best therapeutic option.


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Martin Tamarit, MD; Rosario Navarro, MD; Lucia Alcazar, MD

From the Department of Neurosurgery, Hospital Universitario de Getafe, Madrid, Spain.

Corresponding author: Martin Tamarit, MD, Calle Amparo, 90 4 B, 28012 Madrid, Spain. E-mail:
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Author:Tamarit, Martin; Navarro, Rosario; Alcazar, Lucia
Publication:Ear, Nose and Throat Journal
Article Type:Case study
Geographic Code:4EUSP
Date:Dec 1, 2010
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