CT,MRI,and 18 F-FDG PET/CT findings of malignant peripheral nerve sheath tumor of the head and neck

Abstract

Background

Malignant peripheral nerve sheath tumor (MPNST) is a highly malignant tumor and rarely occurs in the head and neck.

Purpose

To describe the imaging features of MPNST of the head and neck.

Material and Methods

We retrospectively analyzed computed tomography (CT; n = 14), magnetic resonance imaging (MRI; n = 16), and ¹⁸F-FDG PET/CT (n = 5) imaging features of 18 MPNSTs of the head and neck in 17 patients. Special attention was paid to determine the nerve of origin from which the tumor might have arisen.

Results

All lesions were well-defined (n = 3) or ill-defined (n = 15) masses (mean, 6.1 cm). Lesions were at various locations but most commonly the neck (n = 8), followed by the intracranial cavity (n = 3), paranasal sinus (n = 2), and orbit (n = 2). The nerve of origin was inferred for 11 lesions: seven in the neck, two in the orbit, one in the cerebellopontine angle, and one on the parietal scalp. Attenuation, signal intensity, and enhancement pattern of the lesions on CT and MRI were non-specific. Necrosis/hemorrhage/cystic change within the lesion was considered to be present on images in 13 and bone change in nine. On ¹⁸F-FDG PET/CT images, all five lesions demonstrated various hypermetabolic foci with maximum standard uptake value (SUV_max) from 3.2 to 14.6 (mean, 7.16 ± 4.57).

Conclusion

MPNSTs can arise from various locations in the head and neck. Though non-specific, a mass with an ill-defined margin along the presumed course of the cranial nerves may aid the diagnosis of MPSNT in the head and neck.

Keywords

Head/neck malignant peripheral nerve sheath tumor (MPSNT)computed tomography (CT)magnetic resonance imaging (MRI)positron emission tomography (PET)

Introduction

Malignant peripheral nerve sheath tumor (MPNST), defined as any malignant tumor arising from peripheral nerves or differentiating along the lines of nerve sheath elements such as Schwann cells, perineural cells, or fibroblasts (1,2), is a rare, highly malignant tumor that makes up approximately 5–10% of all soft tissue sarcomas (1,3). About 20–50% are associated with type 1 neurofibromatosis (NF-1) although the sporadic form is more common (2,4 –6). In addition, 10% occur in patients with a history of radiation exposure (7).

Fifteen percent of MPNSTs occur in the head and neck (3) and comprise 2–6% of head and neck sarcomas (8). Due to the anatomical and functional complexity, MPNSTs of the head and neck are reported to have worse prognosis with the reported 5-year survival rate of 46.5% (3). Except for a limited number of case reports (9,10), most previous reports on MPNSTs of the head and neck focused on clinicopathological features (3,11) and imaging features were not the major concern. The purpose of this study was to investigate computed tomography (CT), magnetic resonance imaging (MRI), and ¹⁸F-FDG positron emission tomography (PET)/CT findings in 17 patients with histologically proven MPNST of the head and neck.

Material and Methods

Patients

The institutional review board of our hospital approved this study and informed consent was waived in accordance with the requirements of a retrospective study. Between February 1999 and May 2014, 17 patients (11 boys/men, 6 girls/women; mean age, 33 years; age range, 6–69 years) with pathologically proven MPNST (n = 14) or malignant triton tumor (MTT; n = 3) in the head and neck were identified by searching the electronic medical records of our hospital. We included patients with MTT because it is defined as an MPNST with rhabdoid differentiation (9).

Imaging techniques

CT scanning was performed in 14 patients and MRI in 15. Both CT and MRI were performed on 12 patients. CT scans were obtained in the axial plane using various models of a helical CT scanner (HiSpeed Advantage, LightSpeed QX/i, LightSpeed 16 or LightSpeed VCT; GE Healthcare, Milwaukee, WI, USA) with 1–3-mm section thickness. CT scans were obtained before (n = 10) and/or after (n = 12) intravenous administration of iodinated contrast material. Reformatted or direct coronal CT scans were available for review for most patients. MRI of the face and neck was performed using a 1.5T (Signa Advantage Horizon, GE Healthcare) or 3T (Intera Achieva, Philips Healthcare, Best, The Netherlands) to produce precontrast T1-weighted (T1W) spin-echo images (TR/TE/NEX, 400–560 ms/10–14 ms/2) and T2-weighted (T2W) fast spin-echo images with fat saturation (TR/TE/NEX, 2500–4500 ms/80–110 ms/1), followed by contrast-enhanced T1W spin-echo images with fat saturation after intravenous injection of 0.1 mmol/kg gadopentetate dimeglumine (Magnevist; Bayer Healthcare, Berlin, Germany), gadoterate meglumine (Dotarem; Guerbet, Aulnay-sous-Bois, France), or gadobutrol (Gadovist; Bayer Healthcare). In all sequences, images were obtained in the axial plane with 3–4-mm section thickness and 0.3–1-mm intersection gap. In addition, images in the sagittal and/or coronal planes were obtained for most patients. Diffusion-weighted imaging (DWI) was available for review in five patients. DWI was performed before contrast-enhanced MRI by using a single-shot echo-planar imaging sequence (TR/TE, 5100/137 ms; matrix size, 96 × 128; section thickness, 3–4 mm; slice gap, 0.3–0.4 mm; field of view, 200 × 200 mm). The b-values were 0 s/mm² and 1000 s/mm².

Five patients underwent ¹⁸F-FDG PET/CT using two different PET/CT scanners (Discovery LS or Discovery STe; GE Healthcare). Following whole-body CT scanning, performed 60 min after intravenous injection of ¹⁸F-FDG (5.5 MBq/kg) with 3.75–5-mm section thickness, emission scans were obtained from thigh to head at 2.5–4 min per frame in 2D or 3D mode. Attenuation-corrected PET images (voxel size 4.3 × 4.3 × 3.9 mm or 3.9 × 3.9 × 3.3 mm) were reconstructed using CT data using an ordered-subsets expectation maximization algorithm (20–28 subsets, 2 iterations). Commercial software (Advantage Workstation; GE Healthcare) was used to co-register separate CT and PET scan data.

Imaging analysis

All CT, MR, and ¹⁸F-FDG PET/CT images were retrospectively reviewed to consensus by a dedicated head and neck neuroradiologist and a general neuroradiologist who had been practicing in the field for 27 years and 1 year, respectively. We investigated CT and MRI characteristics focusing on size, margin, peritumoral edema, location and nerve of origin, internal architecture, and enhancement pattern of the lesion. Lesion size was measured at the greatest diameter. Lesion margins were classified as well-defined or ill-defined. Peritumoral edema was considered to be present when there was a hyperintense signal surrounding the lesion on T2W MR images or the attenuation of the adipose tissue adjacent to the lesion was increased on CT scans. By careful analysis of the lesion location and growth pattern, we determined the nerve from which the tumor might have originated. For internal architecture, we compared lesion attenuation on pre-contrast CT scans with adjacent muscle. Calcification within the lesion was determined on pre-contrast CT scans. Signal intensity of the lesion on T1W and T2W MR images was compared with the cerebral cortex. On post-contrast CT and MRI, enhancement patterns of the solid portions were categorized as homogeneous or heterogeneous. Degree of enhancement was graded as: mild, when enhancement was similar to the adjacent muscle; moderate, when enhancement was greater than the muscle but less than the sinonasal mucosa; or marked, when enhancement was similar to or greater than the sinonasal mucosa. The presence of necrosis/hemorrhage/cystic changes were determined and defined as the area of no enhancement. Bone change was also determined and classified as frank destruction for bone that was irregularly interrupted, shattered, or infiltrated; and pressure remodeling, when the bone appeared to be smoothly pushed away by the lesion with cortical thinning. For analyzing DWI, an apparent diffusion coefficient (ADC) map was generated from the b = 0 and 1000 s/mm² datasets. For each lesion, a circular region of interest (ROI) of 40–50 mm² was placed within the solid component to calculate mean and minimum ADCs.

On ¹⁸F-FDG PET/CT scans, FDG uptake patterns were categorized visually as homogenous or heterogeneous. Maximum standard uptake value (SUV_max) was measured by placing a circular ROI of 10 mm² within the lesion.

Results

Clinical features

Of 17 patients, MPNST occurred sporadically in 13 (mean age, 36 years) and were associated with NF-1 in four (mean age, 24 years). A palpable mass or swelling was the most common presenting symptom in nine patients, followed by visual loss in two and hoarseness, hemiparesis, headache, diplopia, nasal obstruction, and hearing loss in one each. At diagnosis, two patients had lung metastasis. Fourteen patients were treated by surgery with (n = 10) and without (n = 4) adjuvant chemoradiation and two patients received palliative chemoradiation. The remaining one patient refused treatment and was lost to follow-up. During a follow-up of 1–208 months (mean, 37 months), six of the 16 treated patients died of the disease with a mean survival of 14 months (range, 2–31 months), five were alive with disease, and five were alive with no evidence of disease. In the five patients alive with disease, tumor recurred at the primary site in two and as spinal cord metastasis in one.

Imaging features

Of the 18 analyzed tumors, 16 were in patients with a single lesion and two in a patient with NF-1. Table 1 summarizes the general features of these 18 tumors. All lesions were well-defined (n = 3) or ill-defined (n = 15) soft-tissue masses, in the size range of 1.9–18.4 cm (mean, 6.1 cm). Peritumoral edema was seen in six, the margin of which were ill-defined in five and well-defined in one. Lesion locations were neck (n = 8; Figs. 1 and 2), intracranial cavity (n = 3; Figs. 3 and 4), orbit (n = 2; Fig. 5), and paranasal sinus (n = 2; Fig. 6). The tongue, temporal bone, and scalp were each the site of single lesion. Of the three intracranial lesions, two were intra-axial (Fig. 3) and one extra-axial at the cerebellopontine angle/Meckel's cave (Fig. 4). The nerve of origin could be inferred from imaging features for 11 (61%) of 18 lesions: six lesions seemed to originate from the trigeminal nerve and its branches (Figs. 2, 4, and 5), two from the vagus nerve and its branches, two from the brachial plexus, and one from the sympathetic nerve (Fig. 1). In seven lesions, determination of the nerve of origin failed.

Table 1.

Summary of general imaging features of 18 MPNSTs of the head and neck.

Imaging features	Lesions (n)
Margin
Well-defined	3
Ill-defined	15
Size (cm) Mean, 6.1 (range, 1.9–18.4)
≤4	7
>4	11
Peritumoral edema
Yes	6
No	12
Location
Neck	8
Intracranial cavity	3
Orbit	2
Paranasal sinus	2
Tongue	1
Temporal bone	1
Scalp	1
Nerve of origin
Trigeminal nerve (n = 6)
Main trunk/ganglionic segment*	1
Frontal nerve of ophthalmic nerve^†	2
Supraorbital branch of frontal nerve of ophthalmic nerve^‡	1
Middle or posterior alveolar nerve of maxillary nerve^§	1
Muscular branch of mandibular nerve^§	1
Vagus nerve (n = 2)
Main trunk^§	1
Recurrent laryngeal nerve^§	1
Brachial plexus^§	2
Sympathetic nerve^§	1
Undetermined	7

Tumor arising from the nerve in the cerebellopontine angle.

^†Tumors arising from the nerve in the orbit.

^‡Tumor arising from the nerve on the scalp.

^§Tumors arising from the nerve in the neck.

Fig. 1.

MPNST in the poststyloid parapharyngeal space of the neck in a 13-year-old boy with NF-1. (a) Axial T2W MR image with fat suppression shows a large, ill-defined soft tissue mass (M) with heterogeneous signal intensity in the poststyloid parapharyngeal space of the right neck. Mass contains a large area of cystic or necrotic change and displaces the internal carotid artery (open arrow) and internal jugular vein (solid arrow) laterally, suggesting origin from the sympathetic nerve. Smaller mass (V) posterolateral to the main lesion was coexistent vagus nerve neurofibroma. Note multiple neurofibromas with high signal intensity in other neck parts. Arrowhead indicates external carotid artery. (b) On coronal contrast-enhanced CT scan, mass (M) is ill-defined and grows longitudinally, laterally displacing the internal jugular vein (arrows). As on MRI, CT demonstrates a large area of cystic or necrotic change within the mass. Solid component in the periphery of the mass shows mild to moderate heterogeneous enhancement.

Fig. 2.

MPNST in the buccal space of the neck in an 8-year-old girl. (a, b) Coronal and axial T2W images with fat suppression show a large, lobulated soft tissue mass (M) with homogeneous high signal intensity, predominantly in the left buccal space. Mass grows along the posterolateral border of maxilla with a small tail toward the pterygopalatine fossa (arrow in b), suggesting origin from the maxillary division of trigeminal nerve, probably posterior or middle superior alveolar nerve. Mass causes pressure remodeling of the posterolateral wall of the adjacent maxillary sinus (open arrow in b).

Fig. 3.

MPNST in the brain in a 59-year-old man. (a) Axial T2W and (b) contrast-enhanced T1W images with fat suppression show a large, well-defined mass with significant peritumoral edema in the right frontal lobe. Mass contains large irregular area of necrosis (asterisks). Solid portion is heterogeneously hyperintense to the cerebral cortex on T2W image (a) with moderate to marked heterogeneous enhancement on contrast-enhanced image (b). MRI features are similar to high-grade glioma. Meningeal enhancement along the frontoparietal convexity (arrows) represents dural thickening after craniotomy for traumatic head injury.

Fig. 4.

Malignant triton tumor in the cerebellopontine angle in a 6-year-old boy. (a) Axial T2W and (b) contrast-enhanced fat-suppressed T1W images show a large, well-defined, dumbbell-shaped mass in the left cerebellopontine angle and Meckel's cave along the main trunk and ganglionic segment of trigeminal nerve, indenting the adjacent brain stem and cerebellum without significant edema. Mass contains large area of hemorrhage (asterisks). Solid portion is heterogeneously hyperintense to the cerebral cortex on T2W image (a) with moderate to marked heterogeneous enhancement on contrast-enhanced image (b). Mass caused pressure remodeling of the adjacent temporal bone (not shown).

Fig. 5.

MPNST in the orbit in a 51-year-old woman. (a) Contrast-enhanced axial CT scan shows an ill-defined soft tissue mass (M) with heterogeneous mild to moderate enhancement in the superomedial aspect of the right orbit. Mass causes pressure remodeling of the adjacent medial wall of the bony orbit (arrowhead). (b) Coronal T2W and (c) contrast-enhanced T1W images with fat suppression demonstrate eyeball that is partly indented and displaced inferolaterally by the mass (M). Medial (arrows) and superior (open arrows) rectus muscles are invaded by the mass. Mass has mixed isointensity and hyperintensity on the T2W image (b) and heterogeneous mild to moderate enhancement on the contrast-enhanced image (c). Frontal nerve, a branch of the ophthalmic division of trigeminal nerve, is presumed nerve of origin because the mass is in the superior orbit between the orbital roof and the superior rectus muscle. (d) Axial FDG PET/CT image shows marked homogeneous FDG uptake within the mass (M; SUV_max, 8.0).

Fig. 6.

MPNST in the paranasal sinus in a 65-year-old man. (a) Coronal non-contrast CT scan shows an ill-defined mass in the left frontoethmoidal sinus. Multiple irregular calcifications in various sizes are within the mass (arrows). Bones outlining the mass are partly destroyed and eroded (open arrows). (b) Coronal contrast-enhanced T1W image with fat suppression demonstrates heterogeneous moderate to marked enhancement of the mass (M). Hypointense signal (arrow) represents intratumoral calcifications. There is fluid retention in the frontal sinus (asterisk) secondary to sinus obstruction.

Table 2 summarizes the detailed CT, MRI, and 18F-FDG PET/CT imaging characteristics. The lesions showed various density, signal intensity, and enhancement patterns at CT and MRI. One lesion showed calcifications on pre-contrast CT scans (Fig. 6). The mean and minimum ADC values of five lesions were 1.07 ± 0.60 × 10⁻³ mm²/s (range, 0.42–1.90) and 0.85 ±0.52 × 10⁻³ mm²/s (range, 0.20–1.48), respectively. Although two lesions showed mean and minimum ADC values less than 0.6 × 10⁻³ mm²/s, the remaining three disclosed values greater than 1.0 × 10⁻³ mm²/s. On CT and MRI, intratumoral necrosis/hemorrhage/cystic change was considered to be present in 13 lesions. Bone change was seen in nine lesions as either frank destruction (n = 4; Fig. 6) or pressure remodeling (n = 5; Figs. 2 and 5).

Table 2.

Summary of CT, MRI, and ¹⁸F-FDG PET/CT features of 18 MPNSTs.

Imaging features	Lesions (n)
CT
Density on pre-contrast CT (n = 10)
Isoattenuated	8
Hyperattenuated	2
Calcification on pre-contrast CT
Yes	1
No	9
Enhancement pattern on post-contrast CT (n = 12)
Heterogeneous mild to moderate	11
Heterogeneous moderate to marked	1
MRI (n = 16)
T1W imaging
Homogeneous	11
Isointense	9
Hypointense	1
Hyperintense	1
Heterogeneous	5
T2W imaging
Homogeneous	5
Isointense	1
Hyperintense	4
Heterogeneous	11
Enhancement pattern on postcontrast MRI
Homogeneous marked	2
Heterogeneous mild to moderate	1
Heterogeneous moderate to marked	13
ADC (10⁻³ mm²/s, n = 5)
Mean, 1.07 ± 0.60 (range, 0.42–1.90)
Minimum, 0.85 ± 0.52 (range, 0.20–1.48)
≤0.6	2
>1.0	3
Intratumoral hemorrhage/necrosis/cystic change
Yes	13
No	5
Bone change
Yes	9
Frank destruction	4
Pressure remodeling	5
No	9
¹⁸F-FDG PET/CT (n = 5)
Pattern
Homogeneous	3
Heterogeneous	2
Mean SUV_max, 7.16 ± 4.57 (range, 3.2–14.6)
< 4	2
> 6	3

ADC, apparent diffusion coefficient; SUV_max, maximum standard uptake value.

¹⁸F-FDG PET/CT images obtained for five patients demonstrated homogeneous (n = 3) or heterogeneous (n = 2) hypermetabolic foci with a mean SUV_max of 7.16 ± 4.57 (range, 3.2–14.6). The SUV_max correlated well with the histologic grade of the tumors: two with SUV_max of 3.2 and 3.9 were histologically classified as low-grade; one with SUV_max of 6.1 as intermediate-grade (Fig. 5); and two with SUV_max of 8.0 and 14.6 as high-grade.

Discussion

In this study, we tried to investigate the imaging features of MPNST of the head and neck. The tumors were most commonly located in the neck. Although the general morphologic characteristics of the lesions on CT and MRI were non-specific, the nerve of origin could be frequently inferred from images.

Various head and neck locations of MPNST have been reported. According to Ma et al. (3), of the 43 head and neck MPNSTs, tumors most commonly involved the maxilla (n = 12; 27.9%), mandible (n = 5; 11.6%), neck (n = 5; 11.6%), and parotid gland (n = 4; 9.3%). In the study of Loree et al. (8), the neck was most commonly involved (11/17, 65%), similar to our study (8/18, 44%).

Because most MPNSTs are believed to arise from peripheral nerves, the nerve of origin may be inferred from images based on lesion location and growth pattern, as seen in 11 lesions (61%) in this study. Any segments along the nerve can be affected by the tumor. Although recognizing the nerve of origin may not influence the treatment strategies, it might allow for better correlation with clinical signs and provide a clue to the possibility of neurogenic tumor. Several imaging features are useful for lesion localization. In the poststyloid parapharyngeal (or carotid) space, the displacement pattern of the internal carotid artery and internal jugular vein provides clues for differentiating tumors of sympathetic nerve from those of the vagus nerve: the former usually displace both structures laterally (Fig. 1), while the latter displace them anteriorly (12,13). A tail sign is a reliable sign of nerve sheath tumor and refers to the entering and exiting nerve root at the proximal and distal ends of the tumor, mostly well seen on T2W images (12). MPNSTs arising from cranial nerves in the intracranial cavity, as seen in one case at the cerebellopontine angle/Meckel's cave in this study (Fig. 4), are exceptional and often very aggressive. According to Ziadi et al. (14), who reviewed 32 MPNSTs of the intracranial cranial nerve, the vestibulocochlear nerve (15/32) was most commonly involved, followed by trigeminal (10/32) and facial (5/32) nerves.

MPNSTs that arise from brain parenchyma, so-called malignant intracerebral nerve sheath tumors (MINSTs), as seen in two lesions in this study (Fig. 3), are extremely rare, with only 15 cases reported in the literature (10). Schwann cells of the perivascular nerves and pluripotent mesenchymal cells are suggested as the possible tumor source (10,15). Any sites of the brain can be affected and conventional imaging findings of MINSTs are similar to those of high-grade gliomas. MR spectroscopy may provide clues for differentiating glial from non-glial tumors (10).

Although the imaging features of MPNST have been considered non-specific (16), several studies reported imaging features that were useful for distinguishing MPNST from other tumors. Table 3 summarizes MRI features of MPNST previously reported in the literature. According to Demehri et al. (17), MRI findings favoring the diagnosis of MPNST over benign peripheral nerve sheath tumor (BPNST) include large size, ill-defined margins, and peritumoral edema. Wasa et al. (5) also reported large size, peripheral enhancement, perilesional edema, and intratumoral cystic lesion as MRI features favoring the diagnosis of MPNST. Compared with non-neurogenic malignant soft-tissue tumors, Van Herendael et al. (7) reported intermuscular distribution, location on the course of a large nerve, nodular morphology, and overall non-homogeneity as the MRI findings in favor of MPNST. In our study, the features of MPNST are concordant with the mentioned references. Most lesions were ill-defined (15/18, 83%), large (mean, 6.1 cm), and frequently associated with intratumoral necrosis/hemorrhage/cystic changes (13/18, 72%). Bones were frequently affected by the lesion (9/18, 50%), either by frank destruction or pressure remodeling. The incidence of bone involvement in this study was much higher than the reported 20% incidence in the literature (3), which might be related to tumor location frequently in the vicinity of bones of the head and neck. In this study, calcifications, reported to be more common in malignant tumors (6,18), was found in only one lesion. The internal architecture and enhancement pattern of lesions seen on CT and MR images were non-specific and did not provide sufficient information about the histologic nature of the lesion.

Table 3.

Summary of MRI features of MPNST reported in the literature.

	Wasa et al. (5)	Demehri et al. (19)	Van Herendael et al. (7)	Present study
Case number	41	9	35	18
Imaging modality	MRI	MRI	MRI	CT (n = 12) + MRI (n = 16)
Mean size (cm)	10	6.3	9.5	6.1
Location
Head and neck	–	NA	2	18
Others	41		33	–
Margin
Well-defined	31	2	31	3
Ill-defined	10	7	4	15
Peritumoral edema	12	6	9	6
Calcification	NA	NA	NA	1
Necrosis/hemorrhage/cystic change	16	NA	17	13
Bone change	NA	NA	6	9
T1W imaging
Homogeneous	20	0	17	11
Heterogeneous	21	9	18	5
T2W imaging
Homogeneous	9	5	0	5
Heterogeneous	32	4	16	11
Enhancement pattern on postcontrast MRI
Homogeneous	11	NA	17	2
Heterogeneous	14		2	14

NA, not applicable.

The value of DWI has recently been reported. In their study with nine MPNSTs and 22 BPNSTs, Demehri et al. (17) reported that the minimum ADC values were significantly lower in MPNSTs than in BPNSTs, while mean ADC values were not significantly different. According to them, with threshold values for minimum ADC ≤ 1.0 × 10⁻³ mm²/s and an average diameter of ≥4.2 cm, malignancy could be diagnosed with 100% sensitivity (17). Our results are contradictory to theirs. In our study, although two of five MPNSTs had both mean and minimum ADC values less than 0.6 × 10⁻³ mm²/s, the remaining three had even minimum ADC values greater than 1.0 × 10⁻³ mm²/s. Both studies were based on a small series of MPNST and further investigation is warranted to validate the usefulness of DWI. The usefulness of other functional MRI techniques, such as dynamic contrast-enhanced imaging and MR spectroscopy, has also been reported for differentiation between MPNST and BPNST (17,19).

The use of ¹⁸F-FDG PET/CT for management of MPNST is increasing. It is reported to be valuable for staging, restaging, and treatment planning of MPNSTs (20), and also for detection of malignant transformation of benign tumors in patients with NF-1 (21). According to Benz et al. (22), SUV_max is significantly higher in MPNSTs, compared to BPNSTs. At a cutoff of 6.1 SUV_max, the sensitivity and specificity for differentiation between MPNSTs and BPNSTs were 94% and 91%, respectively (22). In the present study, SUV_max correlated well with the histologic tumor grade: the greater the SUV_max, the higher the tumor grade. This relationship should be further elucidated in larger population. ¹⁸F-FDG PET can also assist in guiding targeted needle core biopsies by revealing the most appropriate target tissue (22).

The limitations of this study include a small number of cases for review and its retrospective nature which precluded the uniform use of advanced techniques such as DWI and ¹⁸F-FDG PET/CT. Because the analysis for those modalities was based on a very small number of cases, one needs to be careful about interpreting our results.

In conclusion, MPNST of the head and neck is a rare but aggressive tumor that can arise in various locations, most commonly the neck. Although the imaging findings are non-specific, a mass with an ill-defined margin along the presumed course of the cranial nerves may aid the diagnosis of MPSNT in the head and neck.

Footnotes

Declaration of Conflicting Interests

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

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

References

Wong

Hirose

Scheithauer

et al.

Malignant peripheral nerve sheath tumor: analysis of treatment outcome. Int J Radiat Oncol Biol Phys 1998; 42: 351–360.

Weiss

Goldblum

. Enzinger and Weiss's Soft Tissue Tumors, 5th ed. St. Louis, MO: Mosby, 2008, pp. 903–944.

Shan

et al.

Malignant peripheral nerve sheath tumours in the head and neck region: retrospective analysis of clinicopathological features and treatment outcomes. Int J Oral Maxillofac Surg 2014; 43: 924–932.

Evans

Baser

McGaughran

et al.

Malignant peripheral nerve sheath tumours in neurofibromatosis 1. J Med Genet 2002; 39: 311–314.

Wasa

Nishida

Tsukushi

et al.

MRI features in the differentiation of malignant peripheral nerve sheath tumors and neurofibromas. Am J Roentgenol 2010; 194: 1568–1574.

Lin

Martel

. Cross-sectional imaging of peripheral nerve sheath tumors: characteristic signs on CT, MR imaging, and sonography. Am J Roentgenol 2001; 176: 75–82.

Van Herendael

Heyman

Vanhoenacker

et al.

The value of magnetic resonance imaging in the differentiation between malignant peripheral nerve-sheath tumors and non-neurogenic malignant soft-tissue tumors. Skeletal Radiol 2006; 35: 745–753.

Loree

North

Jr. Werness

et al.

Malignant peripheral nerve sheath tumors of the head and neck: analysis of prognostic factors. Otolaryngol Head Neck Surg 2000; 122: 667–672.

Ahsan

Lee

Ah-See

et al.

Malignant peripheral nerve sheath tumor of the paranasal sinuses. Ear Nose Throat J 2004; 83: 699–701.

10.

Ramalingam

Nair

Mandal

. Malignant peripheral nerve sheath tumor of the oral cavity. J Oral Maxillofac Surg 2012; 70: e581–585.

11.

Minovi

Basten

Hunter

et al.

Malignant peripheral nerve sheath tumors of the head and neck: management of 10 cases and literature review. Head Neck 2007; 29: 439–445.

12.

Anil

Tan

T-Y

. CT and MRI evaluation of nerve sheath tumors of the cervical vagus nerve. Am J Roentgenol 2001; 176: 75–82.

13.

Anil

Tan

. Imaging characteristics of schwannoma of the cervical sympathetic chain: a review of 12 cases. Am J Neuroradiol 2010; 31: 1408–1412.

14.

Ziadi

Saliba

. Malignant peripheral nerve sheath tumor of intracranial nerve: a case series review. Auris Nasus Larynx 2010; 37: 539–545.

15.

Beauchesne

Mosnier

Schmitt

et al.

Malignant nerve sheath tumor of the right cerebral peduncle: case report. Neurosurgery 2004; 54: 500–503. discussion 503–504.

16.

Levine

Huntrakoon

Wetzel

. Malignant nerve-sheath neoplasms in neurofibromatosis: distinction from benign tumors by using imaging techniques. Am J Roentgenol 1987; 149: 1059–1064.

17.

Demehri

Belzberg

Blakeley

et al.

Conventional and functional MR imaging of peripheral nerve sheath tumors: initial experience. Am J Neuroradiol 2014; 35: 1615–1620.

18.

Yang

W-L

Tiu

C-M

Chou

Y-H

Chang

C-Y

. Imaging presentatin of malignant peripheral nerve sheath tumor at sacral region. J Med Ultrasound 2011; 19: 52–56.

19.

Fayad

Wang

Blakeley

et al.

Characterization of peripheral nerve sheath tumors with 3T proton MR spectroscopy. Am J Neuroradiol 2014; 35: 1035–1041.

20.

Khiewvan

Macapinlac

Lev

et al.

The value of ¹⁸F-FDG PET/CT in the management of malignant peripheral nerve sheath tumors. Eur J Nucl Med Mol Imaging 2014; 41: 1756–1766.

21.

Chirindel

Chaudhry

Blakeley

et al.

¹⁸F-FDG PET/CT qualitative and quantitative evaluation in neurofibromatosis type 1 patients for detection of malignant transformation: comparison of early to delayed imaging with and without liver activity normalization. J Nucl Med 2015; 56: 379–385.

22.

Benz

Czernin

Dry

et al.

Quantitative F18-fluorodeoxyglucose positron emission tomography accurately characterizes peripheral nerve sheath tumors as malignant or benign. Cancer 2010; 116: 451–458.