From the archives of the AFIP. Imaging of musculoskeletal neurogenic tumors: radiologic-pathologic correlation

Intrathoracic malignant peripheral nerve sheath tumors: imaging features and implications for management

Background

The aim of the study was to analyze the clinical and imaging characteristics of primary intrathoracic malignant peripheral nerve sheath tumors (MPNSTs).

Patients and methods.

In this institutional review board (IRB)-approved retrospective study, clinical and imaging features of 15 patients (eight men; mean age 50 years [range 18–83)] with pathologically proven malignant peripheral nerve sheath tumors seen from January 1999 to December 2011 were analyzed. Imaging features (CT in 15, MRI in 5 and PET/CT in 4) of primary tumors were evaluated by three radiologists and correlated with clinical management.

Results

Of the 15 tumors, six were located in the mediastinum (two each in anterior, middle and posterior mediastinum), four in chest wall, two were paraspinal, and three in the lung. Four patients had neurofibromatosis-1 (NF1); four tumors had heterologous rhabdomyoblastic differentiation (malignant triton tumor). Masses typically were elongated along the direction of nerves, with mean size of 11 cm. The masses were hypo- or isodense to muscles on CT, isointense on T1-weighted images, hyperintense on T2-weighted images and intensely fluorodeoxyglucose (FDG) avid (mean standardized uptake value [SUV]_max of 10.5 [range 4.4–23.6]). Necrosis and calcification was seen in four tumors each. Finding of invasion of adjacent structures on imaging led to change in management in seven patients; patients with invasion received chemoradiation.

Conclusions

Intrathoracic MPNSTs appear as large elongated masses involving mediastinum, lung or chest wall. Radiological identification of invasion of adjacent structures is crucial and alters therapy, with patients with invasion receiving neoadjuvant or adjuvant chemoradiation.

The role of MRI in image-guided needle biopsy of focal bone and soft tissue neoplasms

Magnetic resonance imaging (MRI) plays a critical role in the management pathway of both soft tissue and bone neoplasms, from diagnosis through to post-treatment follow-up. There are a wide range of surgical, oncological, and combined treatment regimes but these rely on accurate histopathological diagnosis. This article reviews the role of MRI in the planning of image-guided needle biopsy for suspected soft tissue and bone tumors.

Benign soft tissue tumors in children

Soft tissue masses in children are common, yet can pose a diagnostic dilemma for the orthopedic surgeon who is asked to evaluate them. Although most lesions are dysplastic or benign, some soft tissue sarcomas are seen in the pediatric population. An understanding of the clinical presentation and imaging findings can guide the surgeon decide on the need for a biopsy and formulate an appropriate treatment plan.

Peroneal nerve: Normal anatomy and pathologic findings on routine MRI of the knee

Background

Peroneal nerve lesions are not common and are often exclusively assessed clinically and electromyographically.

Methods

On a routine MR examination without dedicated MR-neurography sequences the peroneal nerve can readily be assessed. Axial T1-weighted sequences are especially helpful as they allow a good differentiation between the nerve and the surrounding fat.

Results

The purpose of this article is to review the normal anatomy and pathologic conditions of the peroneal nerve around the knee.

Conclusion

In the first part the variable anatomy of the peroneal nerve around the knee will be emphasized, followed by a discussion of the clinical findings of peroneal neuropathy and general MR signs of denervation. Six anatomical features may predispose to peroneal neuropathy: paucity of epineural tissue, biceps femoris tunnel, bifurcation level, superficial course around the fibula, fibular tunnel and finally the additional nerve branches. In the second part we discuss the different pathologic conditions: accidental and surgical trauma, and intraneural and extraneural compressive lesions.

Teaching Points

• Six anatomical features contribute to the vulnerability of the peroneal nerve around the knee.

• MR signs of muscle denervation within the anterior compartment are important secondary signs for evaluation of the peroneal nerve.

• The most common lesions of the peroneal nerve are traumatic or compressive.

• Intraneural ganglia originate from the proximal tibiofibular joint.

• Axial T1-weighted images are the best sequence to visualise the peroneal nerve on routine MRI.

Paravertebral high cervical chordoma. A case report

Spinal chordomas are more often located on the midline and are associated with marked destruction of the vertebral bodies. We report a rare case of large cervical (C2-C3) right lateral paravertebral chordoma extending into the spinal canal through a very enlarged intervertebral foramen. The tumor was initially diagnosed as a mucous adenocarcinoma on a percutaneous needle biopsy. However, the neuroradiological features, including the well-defined tumor margins, the regular and sclerosing lytic bone changes with regular enlargement of the intervertebral C2-C3 foramen, were in favor of a more slowly growing lesion, such as schwannoma or neurofibroma. At surgery a well-demarcated capsulated tumor involving the nerve root was partially resected. Histology was in favor of a low-grade chordoma (Ki-67/MIB-1<1%). Postoperative proton beam therapy was also performed. The differential neuroradiological diagnosis is discussed.

Imaging-pathologic correlation of diseases in the axilla

OBJECTIVE

This article reviews the imaging and histopathologic findings of various axillary diseases and suggests management guidelines for radiologists based on imaging findings with clinical correlation.

CONCLUSION

Although axillary diseases may reveal nonspecific imaging findings, a knowledge of the characteristic radiologic manifestations of specific diseases according to anatomic origin (nodal, accessory breast, adipocytic, fibrous, nerve, vascular, stromal, and dermal) and postsurgical lesions aids in establishing an appropriate differential diagnosis and determining whether intervention is necessary.

Plexiform neurofibroma of the wrist: imaging features and when to suspect malignancy

Plexiform neurofibromas are essentially pathognomonic for neurofibromatosis type 1 (NF1), occurring when there is diffuse involvement along a nerve segment and its branches. Transformation into a malignant peripheral nerve sheath tumour (MPNST) is a major cause of mortality in NF1 patients. These tumours are highly aggressive and particularly difficult to diagnose in NF1 patients due to the clinical overlap between benign and malignant lesions. We present a case of a plexiform neurofibroma and discuss the typical imaging characteristics on ultrasound, CT, and MRI, including the target sign and continuity with the parent nerve. Certain imaging features should raise suspicion for malignancy however, these modalities may not always reliably differentiate between benign and malignant lesions. Recent studies show a very high negative predictive value for FDG-PET making it quite useful in excluding malignancy. In positive scans, PET/CT aids in guiding biopsy to the most metabolically active area of the tumour.

Detection of peripheral nerve pathology: comparison of ultrasound and MRI

OBJECTIVE

To compare accuracy of ultrasound and MRI for detecting focal peripheral nerve pathology, excluding idiopathic carpal or cubital tunnel syndromes.

METHODS

We performed a retrospective review of patients referred for neuromuscular ultrasound to identify patients who had ultrasound and MRI of the same limb for suspected brachial plexopathy or mononeuropathies, excluding carpal/cubital tunnel syndromes. Ultrasound and MRI results were compared to diagnoses determined by surgical or, if not performed, clinical/electrodiagnostic evaluation.

RESULTS

We identified 53 patients who had both ultrasound and MRI of whom 46 (87%) had nerve pathology diagnosed by surgical (n = 39) or clinical/electrodiagnostic (n = 14) evaluation. Ultrasound detected the diagnosed nerve pathology (true positive) more often than MRI (43/46 vs 31/46, p < 0.001). Nerve pathology was correctly excluded (true negative) with equal frequency by MRI and ultrasound (both 6/7). In 25% (13/53), ultrasound was accurate (true positive or true negative) when MRI was not. These pathologies were typically (10/13) long (>2 cm) and only occasionally (2/13) outside the MRI field of view. MRI missed multifocal pathology identified with ultrasound in 6 of 7 patients, often (5/7) because pathology was outside the MRI field of view.

CONCLUSIONS

Imaging frequently detects peripheral nerve pathology and contributes to the differential diagnosis in patients with mononeuropathies and brachial plexopathies. Ultrasound is more sensitive than MRI (93% vs 67%), has equivalent specificity (86%), and better identifies multifocal lesions than MRI. In sonographically accessible regions ultrasound is the preferred initial imaging modality for anatomic evaluation of suspected peripheral nervous system lesions.

Benign Schwannoma Mimicking Metastatic Lesion on F-18 FDG PET/CT in Differentiated Thyroid Cancer

We report a case of benign schwannoma mimicking metastatic carcinoma. A 55-year-old female with papillary thyroid carcinoma underwent total thyroidectomy. F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) demonstrated a focal hypermetabolic lesion with maximum standardized uptake value (SUVmax) 5.3 at the right chest wall. Conventional chest CT demonstrated a 5.4 cm ovoid mass lesion between the intercostal muscles and liver. Pathology revealed a schwannoma by tumor excision. This case demonstrates that benign schwannoma may demonstrate FDG uptake mimicking metastatic carcinoma.

Tumours and pseudotumours of the soft tissue in adults: perspectives and current role of sonography

Soft tissue tumours of the musculoskeletal system are reported relatively frequently. The quality of the information gained from different imaging modalities (Doppler sonography, multislice CT, MRI spectroscopy, and diffusion MRI) means that in a growing number of situations, we can envisage determining with great accuracy not only the usual information of tumour size and topography, but often the exact nature of the tissue, almost always identifying whether a lesion is aggressive or not. Of all these techniques, Doppler sonography has become the most widely used due to the striking improvements in its sensors, especially for superficial applications. Some other recent developments are: panoramic imaging, elastography (although its current contribution is still to be determined but it seems to offer promising potential), and, most importantly, specific contrast agents. These techniques have considerably refined the quality of the information obtained, and have particularly enhanced the degree of sensitivity with which lesion progression can be assessed. Ultrasonography is the very first investigation in our protocol. It is also very often used to close investigations, as it accurately guides core needle biopsy from these generally accessible lesions. The purpose of this article is to bring together updated information on the various collections of sonographic features seen in soft tissue tumours and pseudotumours and to emphasise the considerable contributions of these new technological developments, in particular contrast-enhanced sonography. The discussion will follow the World Health Organisation's anatomical pathology classifications of soft tissue tumours. We will close with a synthesis that summarises the main steps in our diagnostic process.

Bladder schwannoma -- a case presentation

Bladder schwannomas are exceedingly rare, benign or malignant, nerve sheath tumors that are most often discovered in patients with a known diagnosis of Neurofibromatosis type 1 (NF1). A few sporadic case reports of bladder schwannoma have been published in urologic, obstetric/gynecologic, and pathologic journals. However, this is the first case report in the radiologic literature where computed tomography imaging and radiology-specific descriptions are discussed. Furthermore, the patient presented in this case is only the fifth published patient without NF1 to be diagnosed with a bladder schwannoma, to the best of our knowledge.

Ultrasound of soft tissue masses of the hand

Most soft tissue mass lesions of the hand are benign. Ganglia are the commonest lesions encountered, followed by giant cell tumors of the tendon sheath. Malignant tumors are rare. Often a specific diagnosis can be achieved on imaging by considering the location and anatomical relations of the lesion within the hand or wrist, and assessing its morphology. Magnetic resonance imaging is an excellent modality for evaluating soft tissue tumors with its multiplanar capability and ability to characterize tissue. Ultrasound plays a complementary role to MRI. It is often the initial modality used for assessing masses as it is cheap and available, and allows reliable differentiation of cystic from solid lesions, along with a real time assessment of vascularity. This review describes the US appearances of the most frequently encountered soft tissue masses of the wrist and hand, correlating the findings with MRI where appropriate.

A-Z of malignant peripheral nerve sheath tumors

This article reviews the typical and atypical locations, imaging findings, local recurrence, and metastatic pattern of malignant peripheral nerve sheath tumors (MPNSTs). MPNSTs are rare soft tissue sarcomas, commonly occur in extremities, and are often associated with neurofibromatosis. Distinction between benign and malignant tumors can be challenging on imaging. MPNSTs have a poor prognosis; however, rhabdomyoblastic differentiation (malignant triton tumor), which has imaging features similar to MPNSTs, is associated with even more aggressive behavior.

Entrapment neuropathies in the upper and lower limbs: anatomy and MRI features

Peripheral nerve entrapment occurs at specific anatomic locations. Familiarity with the anatomy and the magnetic resonance imaging (MRI) features of nerve entrapment syndromes is important for accurate diagnosis and early treatment of entrapment neuropathies. The purpose of this paper is to illustrate the normal anatomy of peripheral nerves in the upper and lower limbs and to review the MRI features of common disorders affecting the peripheral nerves, both compressive/entrapment and noncompressive, involving the suprascapular nerve, the axillary nerve, the radial nerve, the ulnar nerve, and the median verve in the upper limb and the sciatic nerve, the common peroneal nerve, the tibial nerve, and the interdigital nerves in the lower limb.

Neurofibromatosis type 1 presenting with plexiform neurofibromas in two patients: MRI features

Neurofibromatosis type 1 (NF1), also known as peripheral neurofibromatosis or von Recklinghausen's disease, is one of the most common genetic disorders. It is inherited in an autosomal dominant pattern. Multiple cutaneous neurofibromas are hallmark lesions of NF1. Localized and plexiform neurofibromas of the paraspinal and sacral region are the most common abdominal neoplasms in NF1. Herein, we report two patients with a known history of NF1 presenting with multiple, extensive localized and plexiform neurofibromas. We describe the important distinguishing features of these tumors as seen on magnetic resonance imaging (MRI), including very bright signal intensity and target sign on T2 weighted images.

Uncommon primary pelvic retroperitoneal masses in adults: a pattern-based imaging approach

There is a broad spectrum of primary pelvic retroperitoneal masses in adults that demonstrate characteristic epidemiologic and histopathologic features and natural histories. These masses may be classified into five distinct subgroups using a pattern-based approach that takes anatomic distribution and certain imaging characteristics into account, allowing greater accuracy in their detection and characterization and helping to optimize patient management. The five groups are cystic (serous and mucinous epithelial neoplasms, pelvic lymphangioma, tailgut cyst, ancient schwannoma), vascular or hypervascular (solitary fibrous tumor, paraganglioma, pelvic arteriovenous malformation, Klippel-Trénaunay-Weber syndrome, extraintestinal GIST [gastrointestinal stromal tumor]), fat-containing (lipoma, liposarcoma, myelolipoma, presacral teratoma), calcified (calcified lymphocele, calcified rejected transplant kidney, rare sarcomas), and myxoid (schwannoma, plexiform neurofibroma, myxoma).Cross-sectional imaging modalities help differentiate the more common gynecologic neoplasms from more unusual masses. In particular, the tissue-specific multiplanar capability of high-resolution magnetic resonance imaging permits better tumor localization and internal characterization, thereby serving as a road map for surgery.

MRI in hypertrophic mono- and polyneuropathies

Different conditions that may lead to enlarged nerves or nerve roots include hereditary motor and sensory neuropathy (HMSN), neurofibromatosis (NF) type 1, chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and intraneural perineurioma. Differential diagnosis of hypertrophic mono- and polyradiculopathies remains challenging but is important because of different treatments and prognosis. Magnetic resonance imaging (MRI) can identify the hypertrophic nerve segments and guide a fascicular biopsy. A fascicular biopsy will often be necessary for precise diagnosis.

Musculoskeletal manifestations of neurofibromatosis type 1

OBJECTIVE

We will describe and illustrate various musculoskeletal manifestations of neurofibromatosis type 1 (NF1) encountered on imaging studies.

CONCLUSION

Because NF1 is one of the most common genetic disorders, radiologists should be familiar with its imaging manifestations.

Peripheral nerve sheath tumors. Benign or malignant? The role of MRI and ultrasonography in a case report

A 31-year-old male patient admitted to another hospital for investigation of a localized painful hump in the medial surface of his left leg. The clinical examination revealed a painful palpable lump in the medial surface of left thigh that was initially thought to be a hematoma due to a history of recent trauma. However, an ultrasound was requested to exclude deep venous thrombosis (DVT). The US examination revealed a heterogeneous, fusiform lesion with elongated proximal and distal projections in close proximity to superficial femoral artery and vein and could not definitely exclude the DVT hypothesis. In a second ultrasound examination performed in our department, a neurogenic origin of the lesion was proposed. A consequent MRI examination confirmed the presence of a fusiform tumor in the anatomic path of the saphenous nerve. This was further confirmed intraoperatively, and pathologically was diagnosed as a malignant peripheral nerve sheath tumor (MPNST). In this present study the role of ultrasonography, the correlation between MRI and ultrasonographic findings are discussed and a review of the literature is presented.

Characteristic ultrasound feature of traumatic neuromas after neck dissection: direct continuity with the cervical plexus

BACKGROUND

Traumatic neuroma may be easily confused with recurrent lymphadenopathy in the neck, causing patient anxiety, need for fine-needle aspiration (FNA), and even surgery. The purpose of this study was to evaluate the ultrasound (US) features that differentiate traumatic neuroma from recurrent lymphadenopathy after lateral neck dissection (LND), focusing on direct continuity with the involved nerve.

METHODS

This study compared US features of 56 traumatic neuromas in 36 consecutive patients, with 56 recurrent lymphadenopathies in 34 consecutive patients who had a previous history of total thyroidectomy and LND for thyroid cancer. Direct continuity of a nerve with a nodule and other US factors of a nodule (the short axis diameter, short-to-long axis ratio, location, shape, margin, echogenicity, vascular flow, hilar line, cystic portion, and echogenic dots) were evaluated in the two groups.

RESULTS

Traumatic neuromas after LND had a prevalence of 17.8% (36/202) on US. Direct continuity with the involved nerve was visible in 98.2% (55/56) of the traumatic neuromas. The involved nerves in these traumatic neuromas were either terminal type (4/55, 7.3%) or spindle type (51/55, 92.7%). The short axis diameters, short-to-long axis ratio, location, shape, margin, and echogenicity were significantly different (p<0.001) in these two groups. None of the traumatic neuromas had a hilar line, vascular flow, or cystic portion.

CONCLUSIONS

Direct continuity with the cervical plexus may be a characteristic US feature of traumatic neuroma after LND. This feature, along with ancillary findings, may prevent unnecessary surgery as well as painful FNA.

Traumatic neuroma in a patient with breast cancer after mastectomy: a case report and review of the literature

The incidence of traumatic neuroma is extremely low, especially in those patients with breast cancer after mastectomy. There are only 10 cases reported in the literature. We report a patient who developed a palpable nodular mass near the mastectomy scar. The result of excisional biopsy was traumatic neuroma. Review of the literature reveal 10 cases with breast cancer of traumatic neuromas after mastectomy. Traumatic neuroma is a benign lesion and a reparative response of the nerve to injury, either direct/indirect trauma or chronic inflammation. Benign lesions as traumatic neuromas are more rarely seen after mastectomy. However, in order to manage patients' treatment, the most critical problem is to distinguish it from recurrent breast carcinoma. Although assistant examination methods such as ultrasound and computed tomography are valuable to a certain extent, the final diagnosis can only be confirmed on pathologic examination.

Neoplasms associated with germline and somatic NF1 gene mutations

INTRODUCTION

Neurofibromatosis 1 is a tumor predisposition genetic syndrome with autosomal dominant inheritance and virtually 100% penetrance by the age of 5 years. NF1 results from a loss-of-function mutation in the NF1 gene, resulting in decreased levels of neurofibromin in the cell. Neurofibromin is a negative regulator of various intracellular signaling pathways involved in the cellular proliferation. Although the loss of heterozygosity in the NF1 gene may predispose NF1 patients to certain malignancies, additional genetic alterations are a prerequisite for their development. The precise nature of these additional genetic alterations is not well defined, and genetic testing of all malignancies in NF1 patients becomes an essential component of future research in this subset of patients. In addition to germline NF1 mutations, alteration of the somatic NF1 gene is associated with sporadic malignancies such as adenocarcinoma of the colon, myelodysplastic syndrome, and anaplastic astrocytoma.

MATERIALS AND METHODS

A comprehensive English and non-English language search for all articles pertinent to malignancies associated with NF1 was conducted using PubMed, a search engine provided by the U.S. National Library of Medicine and the National Institutes of Health. Key words searched included the following: "malignancies associated with NF1", "tumors associated with NF1", and "NF1 and malignancies". A comprehensive analysis in terms age and mode of presentation, investigation and therapeutic modalities, and outcome of the published data was performed and compared with similar information on the sporadic cases.

RESULTS

Malignancies in NF1 patients typically occur at an earlier age and, with an exception of optic pathway gliomas, certain types of malignancies carry a poor prognosis compared with their sporadic counterparts. Malignancies are the leading cause of death in NF1 patients, resulting in a 10- to 15-year decreased life expectancy compared with the general population.

CONCLUSIONS

The lack of well-defined screening tests for early detection and the nonspecific clinical presentation contributes to a poorer outcome in malignancies associated with NF1. Small study group size, mixed patient population, and a lack of uniformity in reporting research results make comparison of treatment outcome for this group difficult. An International Consensus Meeting to address and recommend best practices for screening, diagnosis, management, and follow-up of malignancies associated with NF1 is needed.

Solitary fibrous tumor: an update on the spectrum of extrapleural manifestations

Solitary fibrous tumor (SFT) is a rare tumor initially believed to be a benign localized pleural tumor of mesothelial origin. Over the past few years, the literature on this tumor has grown tremendously. The tumor is now reported in diverse bodily locations, and recognized to have a wider range of clinical and radiological features. The most common extrapleural sites of the tumor are the orbits and the extremities. Tumors are often well-circumscribed masses, and vary in size from 1 cm to over 30 cm. The admixture of histological components in the tumor, namely, fibrous tissue, cellular components, and highly vascularized areas consisting of numerous closely packed small to medium-sized blood vessels, influence the imaging appearances of the tumor. On magnetic resonance imaging (MRI), the diagnosis of solitary fibrous tumor is suggested by a well-circumscribed mass that has smooth margins, and focal or diffuse hypointense signal on T2-weighted imaging due to fibrous content in the tumor. SFTs demonstrate strong focal or diffuse contrast enhancement due to the highly vascularized areas in the tumor.

MRI findings of mediastinal neurogenic tumors

OBJECTIVE

The objective of this article is to review the clinical, pathologic, and MRI findings of mediastinal neurogenic tumors according to the three tumor origins: the peripheral nerves, sympathetic ganglia, and paraganglia.

CONCLUSION

MRI findings reflect pathologic features of mediastinal neurogenic tumors. Integrating consideration of age and clinical findings of the patient, lesion location, and imaging findings is important in the diagnosis of mediastinal neurogenic tumors.

The pearls and pitfalls of magnetic resonance imaging of the lower extremity

This article is intended for the clinician charged with either diagnosing or treating patients with lower extremity symptoms thought to be of musculoskeletal etiology. It gives a brief overview of the imaging techniques that can be utilized, common pathology, and certain pearls and pitfalls that may be encountered in both ordering and interpreting lower extremity magnetic resonance imaging. While we cannot present a comprehensive discussion of all of the known disorders in the lower extremity, we will choose common disorders to illustrate the diagnostic benefits and limitations of magnetic resonance imaging and provide reasons for choosing certain magnetic resonance imaging techniques.

Adipose lesions of nerve: the need for a modified classification

OBJECT

Adipose lesions of nerve are rare and poorly understood. Their current classification, although not universally accepted, generally includes lipomatosis of nerve with or without localized macrodactyly, and intra- as well as extraneural lipoma. The authors believe that the spectrum of these lesions and their interrelationships are not currently appreciated. They propose an adaptation to the existing framework to illustrate the expanding spectrum of adipose lesions of nerve by considering lipomatosis and lipoma singly or in combination.

METHODS

Fourteen representative cases are presented to demonstrate not only the intraneural and extraneural examples of lipomatosis and lipoma, but also their anatomical combinations.

RESULTS

Based on the cases presented and a careful literature review, a conceptual approach to the classification of adipose lesions of nerve is generated. This approach incorporates the 2 essential lesions, lipomatosis of nerve and lipoma, in both their intra- and extraneural forms. This permits expansion to encompass combinations.

CONCLUSIONS

To press the concept that adipose tumors of nerve are a broad but interrelated spectrum of lesions, the authors propose modification of the present classification system. This approach provides an orderly platform for progress, reflects understanding of these interrelated lesions, and facilitates optimal treatment by distinguishing resectable from nonresectable components.

Extrarenal rhabdoid tumor mimicking a sacral peripheral nerve sheath tumor

Extrarenal rhabdoid tumor is a rare, highly aggressive tumor of childhood with a poor prognosis. It represents <1% of pediatric soft tissue malignancies, typically involving infants . Frequently involved extrarenal sites include deep locations of the neck, abdomen, and paraspinal regions. The presence of "rhabdoid" cells is the characteristic histologic feature. Recent discovery of a specific genetic mutation enables a more accurate diagnosis. We present a case in an adolescent of extrarenal rhabdoid tumor arising within the sacral canal. This appears to be the first reported case of an extrarenal rhabdoid tumor arising within the sacral canal and mimicking a peripheral nerve sheath tumor. While rare, this tumor can be included in the radiologic differential diagnosis of peripheral nerve sheath tumors in children.

CT and MRI evaluation of nerve sheath tumors of the cervical vagus nerve

OBJECTIVE

Nerve sheath tumors arising from the cervical vagus are rare. The purpose of this study was to evaluate the role of CT and MRI in the diagnosis of these uncommon neoplasms.

MATERIALS AND METHODS

The CT and MR studies and clinical data of 11 patients with surgicopathologic evidence of a nerve sheath tumor of the cervical vagus (nine schwannomas [including two ancient schwannomas] and two neurofibromas) who had been referred to our institute from January 1999 through 2009 were retrospectively reviewed. The tumors were evaluated with respect to their location, number, morphology, attenuation and/or signal intensity, enhancement characteristics, and patterns of mass effect.

RESULTS

The tumors were solitary and well circumscribed. On CT, eight tumors were hypodense with poor enhancement, two were predominantly isodense, and a single lesion had multiple cystic areas with enhancing solid components. On MRI, they were heterogeneously bright on T2-weighted images with intense, inhomogeneous postgadolinium enhancement. The "split fat" sign, "entering and exiting nerve" sign, "fascicular" sign, and "hyperintense rim" sign were seen in some patients. The internal or common carotid artery was displaced anteriorly in eight patients, maintained a neutral position in two patients, and was displaced posterolaterally in another patient. In all patients except two, the tumor separated the carotid artery from the internal jugular vein. Vagal schwannomas splayed the carotid bifurcation in three patients.

CONCLUSION

In conclusion, we present the patterns of mass effect and a spectrum of CT and MRI characteristics of nerve sheath tumor of the cervical vagus including observations that are sparingly described in the published literature.

Indeterminate soft-tissue tumors of the hand and wrist: a review based on a clinical series of 39 cases

Soft-tissue masses located at the hand and wrist are a frequent clinical presentation. The majority of these are ganglia, which have characteristic imaging features. Other common masses in which a diagnosis is suggested by imaging include hemangiomas, lipomas, and focal synovitis. The remainder are rare although a diagnosis may be attempted by considering the patients' age and the location. We reviewed 39 soft-tissue masses at the hand and wrist referred to our institution between September 1998 and January 2006 that had indeterminate imaging features. The majority were benign neoplastic lesions with the most common being a giant cell tumor of the tendon sheath, followed by angioleiomyoma, peripheral nerve sheath tumor, fibromatosis, fibroma of tendon sheath, and solitary fibrous tumor. These lesions tend to occur in young adults at the metacarpal level. However, there are no imaging features that can reliably differentiate between benign and malignant tumors.

Peripheral tumor and tumor-like neurogenic lesions

Neoplasms of neurogenic origin account for about 12% of all benign and 8% of all malignant soft tissue neoplasms. Traumatic neuroma, Morton neuroma, lipomatosis of a nerve, nerve sheath ganglion, perineurioma, benign and malignant peripheral nerve sheath tumors (PNST) are included in this group of pathologies. Clinical and radiologic evaluation of patients with neurogenic tumors and pseudotumors often reveals distinctive features. In this context, advanced imaging techniques, especially ultrasound (US) and magnetic resonance (MR) play an important role in the characterization of these lesions. Imaging findings such as location of a soft tissue mass in the region of a major nerve, nerve entering or exiting the mass, fusiform shape, abnormalities of the muscle supplied by the nerve, split-fat sign, target sign and fascicular appearance should always evoke a peripheric nerve sheath neoplasm. Although no single imaging finding or combination of findings allows definitive differentiation between benign from malign peripheric neurogenic tumors, both US and MR imaging may show useful features that can lead us to a correct diagnosis and improve patient treatment. Traumatic neuromas and Morton neuromas are commonly associated to an amputation stump or are located in the intermetatarsal space. Lipomatosis of a nerve usually appears as a nerve enlargement, with thickened nerve fascicles, embedded in evenly distributed fat. Nerve sheath ganglion has a cystic appearance and commonly occurs at the level of the knee. Intraneural perineuroma usually affects young people and manifests as a focal and fusiform nerve enlargement. In this article, we review clinical characteristics and radiologic appearances of these neurogenic lesions, observing pathologic correlation, when possible.

A small intraneural epithelioid malignant peripheral nerve sheath tumour of the median nerve simulating a benign lesion: description of a case and review of the literature

The epithelioid variant of malignant peripheral nerve sheath tumours (MPNSTs) is a very rare malignancy. We describe the case of a 30-year-old man complaining of acute pain in his right elbow, mild distal paraesthesias, and some motor deficiencies. He was discovered as having a small fusiform swelling of the median nerve. In view of its very small size, shape, and nonspecific MRI signal, it had initially suggested a benign lesion. The diagnosis of epithelioid MPNST was made only at the histopathological examination. This malignant neoplasm recurred locally fourteen months after surgery. In addition to describe the above very rare case, we have reviewed the literature on epithelioid MPNSTs clearly involving deep major nerve trunks. This case serves as a warning that, even in major nerve trunks, tiny lesions may in reality be early intraneural MPNSTs which, due to their deep location, must be treated adequately with wide margin surgery since the resection margin status represents one of the major parameters influencing the local control of disease and its clinical outcome.