Intraneural perineurioma. A clonal neoplasm associated with abnormalities of chromosome 22

Case report: Intraneural perineurioma in dogs: a case series and brief literature review

Intraneural perineurioma is an exceptionally rare neoplasm in animals. This case study comprises a series of three cases and a brief literature review focusing on canine intraneural perineurioma. The pathological and immunohistochemical findings are documented, revealing that canine intraneural perineurioma frequently affects adult dogs aged between 3 and 10 years old, with a male predominance. Clinical signs associated with intraneural perineurioma in dogs include spinal pain, lameness, and paresis, resulting from the involvement of spinal nerve roots of the pelvic limbs, brachial plexus, or distal part of the median nerve. Most neoplasms had characteristic pseudo-onion bulb patterns on histopathology. Neoplastic perineurial cells, in most cases, expressed laminin and claudin-1, and NF200 consistently highlighted the central axon. While the immunohistochemical (IHC) profile of intraneural perineurioma in veterinary medicine remains incompletely characterized, the available IHC data from all reported cases suggest that a combination of laminin and claudin-1 immunomarkers, along with distinctive histological features, can assist in establishing a definitive diagnosis of intraneural perineurioma.

Peripheral nerve tumors

The chapter is focused on the neoplastic peripheral nerve lesions, which primarily involve "cranial and paraspinal nerves," as outlined in the CNS volume (WHO_Classification_of_Tumours_Editorial_Board, 2021). These include classic peripheral nerve sheath tumors such as schwannoma, neurofibroma, intraneural perineurioma, and malignant peripheral nerve sheath tumors, with their variants as well as new and more precisely defined entities, including hybrid nerve sheath tumors and malignant melanotic nerve sheath tumor (previously melanotic schwannoma).

What is new in intraneural perineurioma?

Since the initial description of intraneural (IN) perineurioma in 1964, advances in the understanding of the clinical presentation, diagnostic imaging, pathologic features, and genetic underpinnings have changed how this pathology is managed. IN perineuriomas are rare, benign peripheral nerve sheath tumors, most frequently coming to clinical attention when patients present with painless, progressive weakness or sensory loss in adolescence or young adulthood. The gold standard of diagnosis has traditionally been with targeted tissue biopsy demonstrating "pseudo-onion bulb" formation with positive epithelial membrane antigen (EMA) staining. However, modern magnetic resonance imaging is allowing some patients to forgo biopsy. Recent genetic studies of IN perineuriomas have demonstrated common TRAF7 point mutations and rare NF2 mutations, which may present targets for diagnosis or therapy in the future. Current advances have allowed for us to provide improved patient counseling with informed understanding for various clinical scenarios. With the workup and diagnosis now clearly defined, the next frontier is for improving the lives of patients with IN perineuriomas through the interaction between restoration of functional deficits and advances in our understanding of the genetics of this entity.

Hybrid tumors with perineurioma components: a systematic review of the literature and illustrative case

PURPOSE

Hybrid peripheral nerve sheath tumors (HPNST) are a newly recognized class of peripheral nerve sheath tumor, composed of at least two areas characteristic of perineurioma, schwannoma, or neurofibroma. The literature consists only of case reports and small series; therefore, we present an illustrative case and an analysis of all reported cases of HPNST with a perineurioma component in the literature.

METHODS

A systematic search of the literature was performed to identify all reported cases of hybrid perineurioma-schwannoma or perineurioma-neurofibroma in the world's literature. Individual cases were analyzed for demographics, clinical features, imaging, and outcomes.

RESULTS

A total of 159 cases were identified across 41 studies. Hybrid tumors tended to present in mid-adulthood (median 38.5 years), predominantly affected females (57%, 89/156), as a painless (63%, 63/100) mass, or swelling. Ten patients (10/74, 14%) had a history of neurofibromatosis 1, and 2 patients a history of neurofibromatosis 2 (2/74, 3%). The majority (78%, 122/157) of cases occurred superficially, most commonly in the lower extremity (25%, 39/157). Perineurioma-schwannoma was the most reported (86%, 137/159) pathologic diagnosis, with 3 cases presenting with malignant features. Two cases reocurred after resection.

CONCLUSION

HPNST tend to occur in mid-adulthood and present as slowly progressive, painless, superficial masses, with a heterogeneous appearance on imaging. These entities pose a unique diagnostic challenge and likely remain under-recognized in the literature and current clinical practice. They pose low risk of recurrence or malignant transformation, and future work regarding the association with neurofibromatosis and genetic profiles is needed.

Plexal intraneural perineurioma: an analysis of the clinicoradiologic presentation of this rare variant

PURPOSE

Intraneural (IN) perineurioma is a rare benign peripheral nerve sheath tumor, typically presenting as a painless, progressive mononeuropathy in adolescents. A rare plexal variant has been described, although there are little data describing its clinicoradiologic features. Herein, we present the largest case series of plexal IN perineuriomas reported in the literature.

METHODS

Electronic medical records (EMR) from 1990 to 2022 from a single academic institution were reviewed for a diagnosis of IN perineurioma involving the brachial or lumbosacral plexus. This identified 18 patients, of which 17 had available MR imaging. We reviewed the EMR for demographics, clinical presentation, imaging characteristics, and surgical outcomes.

RESULTS

Eighteen patients were identified. Most patients were male (11/18, 61%) and first developed symptoms at the age of 9.6 years (range 7 months to 55 years). Diagnosis occurred on average at the age of 22 years (4-57 years), which is significantly earlier than distal IN perineurioma (p = 0.0096). All patients (100%, 17/17) presented with motor polyneuropathy and muscular atrophy in multiple nerve distributions, with associated sensory loss (12/17, 71%). Most plexal lesions occurred in the brachial plexus (66%, 12/18). Five (29%, 5/17) patients presented with a hand/foot discrepancy, and 5 patients (29%) had a limb length discrepancy. Five patients underwent tendon transfer, of which two had failure of tendon transfer at most recent follow-up (50%, 2/4) due to progression of neurologic loss affecting the donors. Of patients managed nonoperatively, 87% of patients (6/7) with follow-up information demonstrated disease progression with worsening motor function or sensory loss, and 2 patients demonstrated progression on imaging at most recent follow-up.

CONCLUSIONS

Plexal perineurioma represents an uncommon variant of IN perineurioma that presents as a progressive motor and sensory polyneuropathy in childhood or early adolescence. Surgical management remains controversial, and tendon transfer tends to result in poor long-term surgical outcomes.

Practical Approach to Histological Diagnosis of Peripheral Nerve Sheath Tumors: An Update

Peripheral nerve sheath tumors encompass a wide spectrum of lesions with different biological behavior, including both benign and malignant neoplasms as well as the recent diagnostic category, i.e., “atypical neurofibromatous neoplasm with uncertain biologic potential” to be used only for NF1 patients. Neurofibromas and schwannomas are benign Schwann-cell-derived peripheral nerve sheath tumors arising as isolated lesions or within the context of classical neurofibromatosis or schwannomatoses. Multiple tumors are a hallmark of neurofibromatosis type 1(NF1) and related forms, NF2-related-schwannomatosis (formerly NF2) or SMARCB1/LZTR1-related schwannomatoses. Perineuriomas are benign, mostly sporadic, peripheral nerve sheath tumors that show morphological, immunohistochemical, and ultrastructural features reminiscent of perineurial differentiation. Hybrid tumors exist, with the most common lesions represented by a variable mixture of neurofibromas, schwannomas, and perineuriomas. Conversely, malignant peripheral nerve sheath tumors are soft tissue sarcomas that may arise from a peripheral nerve or a pre-existing neurofibroma, and in about 50% of cases, these tumors are associated with NF1. The present review emphasizes the main clinicopathologic features of each pathological entity, focusing on the diagnostic clues and unusual morphological variants.

Nerve conduction assessment and magnetic resonance imaging for the diagnosis of localized hypertrophic neuropathy of the sciatic nerve and the lumbo-sacral plexus

Localized hypertrophic neuropathy (LHN) are slowly growing nerve lesions causing progressive nerve deficit and weakness. We present the case of a 32-year old woman with long history of motor and sensory deficit complains along the sciatic nerve territory. The muscles involved were featured by delay in F waves at nerve conduction assessment. Magnetic resonance imaging (MRI) showed specific patterns, low intense on T1 and abnormally hyper intense on short tau inversion recovery (STIR) and T2, with no obvious enhancement, features compatible with either LHN or intraneural perineurioma (IP) of the sciatic nerve and/or the lumbosacral plexus. Focal thickening and hypertrophy of the sciatic nerve with preserved fascicular configuration and progressive enlargement of the right lumbosacral plexus could be noted. A nerve conduction assessment followed by an MRI eventually allowed to diagnose LHN, without performing a nerve biopsy. Although similar, LHN and IP are two distinct lesions which should be diagnosed and differentiated as soon as possible, to avoid potential complications due to delayed diagnosis and/or misdiagnosis.

Clinical Features, Natural History, and Outcomes of Intraneural Perineuriomas: A Systematic Review of the Literature

BACKGROUND

Intraneural perineurioma is a rare peripheral nerve sheath tumor characterized by localized proliferation of perineurial cells. The literature consists predominantly of case reports and institutional series, with inconsistent and confusing nomenclature. We present a pooled analysis of all reported cases of intraneural perineurioma in the literature.

METHODS

A systematic search of PubMed, MEDLINE, Embase, and Scopus was performed according to PRISMA guidelines to identify all reported cases of intraneural perineurioma in the literature. Individual cases were pooled and analyzed for demographics, clinical features, and outcomes.

RESULTS

A total of 172 cases were identified across 72 studies, of which 149 were found in major peripheral nerves and their branches. Median age of patients at diagnosis and onset of symptoms was 18 years (interquartile range [IQR], 12-34 years) years and 13.5 years (IQR, 8-26 years), respectively, with 54.4% (81/149) being female. The most common sites were the sciatic nerve or its branches (41.9%), median nerve (13.5%), radial nerve (12.2%), and brachial plexus (12.2%). Most patients were managed conservatively (52.9%; 72/136). Among those managed conservatively with available follow-up (n = 31), median follow-up was 11 months, and most (67.7%, n = 21) reported no change in neurologic status, although worsening was noted in 29.0% (9/31). Among surgically managed cases (n = 64), the most common intervention was resection with or without repair (62.5%; 40/64), neurolysis (25%; 16/64), or tendon transfers without resection (12.5%; 8/64). No lesion recurred after surgical resection.

CONCLUSIONS

Intraneural perineurioma represents a benign focal lesion presenting with weakness and atrophy affecting adolescents and young adults. Most cases are managed nonoperatively and surgical treatment strategies are varied.

Recurrent Fusion of the GRB2 Associated Binding Protein 1 (GAB1) Gene With ABL Proto-oncogene 1 (ABL1) in Benign Pediatric Soft Tissue Tumors

BACKGROUND/AIM

Fusions of the ABL proto-oncogene 1 gene (ABL1 in 9q34) are common in leukemias but rare in solid tumors. The most notable is the t(9;22)(q34;q11)/BCR-ABL1 coding for a chimeric tyrosine kinase. We herein report an ABL1-fusion in a pediatric tumor.

MATERIALS AND METHODS

G-banding, fluorescence in situ hybridization, reverse transcription polymerase chain reaction and Sanger sequencing were performed on a soft tissue perineurioma found in the left musculus erector spinae of a child.

RESULTS

A der(4)t(4;9)(q31;q34) and a fusion of the GRB2 associated binding protein 1 (GAB1 in 4q31) gene with ABL1 were found. A literature search revealed 3 more cases with similar genetic and clinicopathological characteristics: a soft tissue perineurioma with t(2;9;4)(p23;q34;q31) and ABL1 rearrangement, a soft tissue angiofibroma with a GAB1-ABL1 chimeric gene, and a solitary fibrous tumor carrying a der(4)t(4;9)(q31.1;q34).

CONCLUSION

GAB1-ABL1 is a recurrent fusion gene in benign pediatric tumors.

Intraneural perineurioma of the median nerve at the elbow: A clinical case

A 31-year-old female patient presented with swelling on the anteromedial aspect of her right elbow with a sensory deficit in the median nerve territory. Biopsies led to the diagnosis of intraneural perineurioma (INP). Surgical excision was performed and followed by an intercalary graft. INP is a rare benign tumor of the peripheral nerves characterized by a multiplication of perineural cells invading the endoneurium. This lesion is often unknown, under-diagnosed, and its treatment is poorly defined. Few cases have been described in the literature; the majority involve the median nerve at the wrist and no references have been found about its localization to the median nerve at the elbow.

[Informative value of ultrasound in the diagnosis of intraneural perineurioma]

OBJECTIVE

To describe clinical and sonographic features of confirmed intraneural perineurioma in 5 patients.

MATERIAL AND METHODS

We report clinical and sonographic features and retrospective follow-up data in 5 patients with intraneural perineurioma verified by biopsy.

RESULTS

In all cases, symptoms were represented by a slowly progressive painless mononeuropathy with muscle atrophy and impaired tendon reflexes. Ultrasound examination revealed locally enlarged cross-sectional area of the nerve that was confirmed by intraoperative visualization.

CONCLUSION

Intraneural perineurioma should be obligatory suspected in case of fusiform thickening of the nerve with locally changed echogenicity. Pooled multiple-center studies with large samples are needed to determine sensitivity and specificity of the main ultrasound parameters including changes in cross-sectional area and echogenicity of the nerve.

Association of intraneural perineurioma with neurofibromatosis type 2

BACKGROUND

Neurofibromatosis type 2 (NF2) is a genetic disorder characterized by mutations of the NF2 tumor suppressor gene that predisposes patients to develop multiple tumors in the peripheral and central nervous system. The most common neoplasms associated with the disease are schwannomas and meningiomas. Both have been shown to contain abnormalities in chromosome 22 and the NF2 gene, suggesting a genetic component to their pathogenesis. Perineuriomas are rare benign tumors arising from the perineural cells. They are commonly classified as intraneural and soft tissue perineuriomas. Several studies have reported mutations in genes on chromosome 22 in both types of perineuriomas, and there are reports of soft tissue perineuriomas associated with NF2 gene mutations. Despite this, perineuriomas are not considered as part of the NF2 constellation of tumors.

METHOD

The electronic medical records were searched for patients with a radiologic or pathologic diagnosis of intraneural perineurioma. Patients with clinical signs and genetic testing consistent with a diagnosis of NF2 were further evaluated.

RESULTS

Of 112 patients meeting inclusion criteria, there were two cases of intraneural perineurioma in patients with NF2 treated at our institution (1.8%). We include a third patient treated at another facility for whom we performed a virtual consultation.

CONCLUSIONS

The rarity of both NF2 and perineuriomas could explain the rarity of perineuriomas in the setting of NF2. Furthermore, there is divergent intraneural and soft tissue perineurioma somatic mutation pathogenesis, and there may be cytogenetic overlap between perineuriomas and multiple tumor syndromes. Our observed occurrence of intraneural perineurioma in the setting of NF2 in several patients provides further evidence of a potential link between the NF2 gene and the development of intraneural perineurioma.

Clinical and Radiological Follow-up of Intraneural Perineuriomas

BACKGROUND

Management of intraneural perineuriomas remains controversial, largely due to the lack of knowledge regarding the natural history of these lesions.

OBJECTIVE

To describe the typical radiological growth pattern of intraneural perineuriomas and to determine how the pattern of growth relates to clinical progression.

METHODS

We performed a retrospective review of the magnetic resonance imaging (MRI) studies and serial clinical examinations of a cohort of patients with biopsy-proven intraneural perineuriomas who had 2 MRI studies at least 2 yr apart. The outcome of interest was radiological growth in length or width of the intraneural perineurioma. Radiological growth was tested for association with clinical progression.

RESULTS

Twenty patients were included in the study. By width, the lesions were on average larger on repeat imaging (P = .009). By absolute length, the lesions were on average longer on repeat imaging (P = .02). By lesion:landmark ratio, there was no difference in length of the lesions between sequential images (P = .09), with 10 (50%) lesions being shorter and 7 (35%) showing no change. No lesions grew to involve a new nerve or division of a nerve on sequential imaging. None of the variables tested were associated with clinical progression.

CONCLUSION

We found that intraneural perineuriomas only rarely grow in length, do not grow to involve new nerves or nerve divisions, and growth does not correlate with clinical progression. These findings have significant ramifications for management of these tumors.

Modern treatment of perineuriomas: a case-series and systematic review

Background

Perineuriomas are rare benign peripheral nerve sheath tumours of perineurial cell origin and can be classified into intraneural and extraneural perineuriomas. They most commonly present a mononeuropathy of gradual onset and slow progression, resulting in progressive neurological deficits like hypoesthesia or motor weakness. Therapy is still variable. Aim of the study was to compare our surgical treatment and our follow-up regime including high-resolution nerve sonography with the current literature to evaluate best treatment of perineuriomas.

Methods

Retrospective analysis of our dataset “peripheral nerve lesion” to identify patients suffering from perineuriomas between 01.01.2012 until 31.12.2018. Surgical treatment and the follow-up examination of three patients were described. Additionally, a systematic review including PubMed, the Cochrane Collaboration Library, Scopus and Google Scholar was performed for literature published between January 1, 1990 and October 31, 2019 independently by 2 authors.

Results

In the first case, the left ulnar nerve was affected. In the second case, the left peroneal nerve and in the third case the right median nerve was affected. High-resolution nerve sonography was performed in each case. All patients underwent interfascicular neurolysis combined with a targeted fascicular biopsy under electrophysiological monitoring. Neurological deficits improved subsidized by rehabilitation. Surgical therapy and the neurological outcome were compared with literature. Systematic review revealed 22 articles, which met the inclusion criteria. Therefore, demographics, surgical treatment and neurological outcome of 77 patients were analysed.

Conclusions

Perineuriomas are rare benign nerve sheath tumours with a slow progression, sometimes difficult to diagnose. Decompression and neurolysis may improve neurological deficits. High resolution nerve sonography might serve as a helpful additional diagnostic tool in this process.

Intraneural perineurioma: a retrospective study of 19 patients

Intraneural perineurioma is a benign neoplasm of peripheral nerve sheath with perineurial cell origin that typically affects teenagers and young adults and tends to result in a motor-predominant neuropathy. The aim of our study is to present the epidemiology, clinical presentation, way of diagnosis and management plan in a consecutive patient series. Ninteen patients diagnosed as having intraneural perineurioma were retrospectively chart reviewed. Diagnosis was done by MRI and/or biopsy with morphological, immunohistochemical staining study confirmation. Patients assessments included gender, age, symptoms, tumor localization, radiological aspect, management and pathological confirmation.Sex ratio was 10 males to 9 females with mean age of 31.2 (15-64). All the patients presented with motor deficit, ten with sensory deficit. Upper limb was involved in 11 cases (among them 4 lesions of brachial plexus), the lower limb in 8 cases. On magnetic resonance imaging, 16 patients showed a nerve enlargement whereas 5 presented with atypical fusiform tumor. Eighteen patients were operated for excision biopsy and/or palliative treatment for their motor deficit. Anatomopathological analysis confirmed the diagnosis in seventeen cases with a morphological pseudo-onion bulb shape and/or specific immunohistochemical assay. One patient had only palliative treatment without excision biopsy. Our data confirmed the equal penetration of intraneural perineurioma to both sex and affected limb. Because of the benignity of the tumor, the surgical treatment focused on optimizing the functional outcome. A prospective study with long term follow-up is required for this under-diagnosed tumor.

Trigeminal hypertrophic interstitial neuropathy presenting as unilateral proptosis, ptosis, tearing, and facial neuralgia

Purpose

To show the utility of MRI and histology in diagnosing rare cases of trigeminal hypertrophic interstitial neuropathy (HIN).

Observations

A 57-year-old African-American woman presented with a 4-year history of right eye proptosis with tearing, headaches, and worsening right-sided trigeminal neuralgia symptoms and jaw pain. HIV and diabetes tests were negative and thyroid function was normal. MRI identified abnormal thickening of all trigeminal nerve divisions and proptosis secondary to right trigeminal nerve V1 division enlargement. The excised tissue contained S-100 positive Schwann cells in an onion-bulb pattern. Headaches resolved, but proptosis and mild trigeminal neuralgia remained 1 year post-surgery.

Conclusions and importance

Trigeminal HIN is very rare, but presents as chronic progressive ocular symptoms with trigeminal neuralgia. Trigeminal nerve hypertrophy is identified by MRI and confirmed histopathologically by detection of Schwann cells in an onion bulb formation.

Clinicoradiological features of intraneural perineuriomas obviate the need for tissue diagnosis

OBJECTIVE

This study aimed to define a set of clinicoradiological parameters with a high specificity for the diagnosis of intraneural perineurioma, obviating the need for operative tissue diagnosis.

METHODS

The authors retrospectively reviewed MR images obtained in a large cohort of patients who underwent targeted fascicular biopsy and included only those patients for whom the biopsy yielded a diagnosis. Clinical and radiological findings were then tested for their ability to predict a tissue diagnosis of intraneural perineurioma. The authors propose a new set of diagnostic criteria, referred to as the Perineurioma Diagnostic Criteria. The sensitivity, specificity, positive predictive value, and negative predictive value of several clinicoradiological methods of diagnosis were compared.

RESULTS

A total of 195 patients who underwent targeted fascicular biopsy were included in the cohort, of whom 51 had a tissue diagnosis of intraneural perineurioma. When the clinicoradiological methods used in this study were compared, the highest sensitivity (0.86), negative predictive value (0.95), and F1 score (0.88) were observed for the decision trees generated in C5.0 and rPart, whereas the highest specificity (1.0) and positive predictive value (1.0) were observed for the Perineurioma Diagnostic Criteria.

CONCLUSIONS

This study identified clinical and radiological features that are associated with a diagnosis of perineurioma. The Perineurioma Diagnostic Criteria were determined to be the following: 1) no cancer history, 2) unifocal disease, 3) moderate to severe hyperintensity on T2-weighted MR images, 4) moderate to severe contrast enhancement, 5) homogeneous contrast enhancement, 6) fusiform shape, 7) enlargement of the involved nerves, and 8) age ≤ 40 years. Use of the Perineurioma Diagnostic Criteria obviates the need for tissue diagnosis when all of the criteria are satisfied.

Intraosseous intraneural perineurioma derived from the inferior alveolar nerve with an abnormality of chromosome 22 and expression of the BCR-ABL fusion gene: report of a case and review of recent literature

BACKGROUND

Perineurioma (PN) is a peripheral nerve disease that primarily develops in the limbs and trunk and very rarely occurs in the oral cavity. PN is classified into two types: intraneural perineurioma (INPN) and soft tissue perineurioma (extraneural perineurioma, ENPN). In this article, we report a patient with mandibular body INPN derived from the perineurium of the inferior alveolar nerve.

CASE PRESENTATION

The patient was a 43-year-old male. He consulted our department for a detailed examination of the right mandibular body. A biopsy was performed at another hospital and he was diagnosed with a schwannoma. At his first visit, hypesthesia extending from the right lower lip to the mental region was recognized and enlargement of the right mandibular canal was confirmed with X-ray CT and MRI. Considering the possibility of future tumor growth, we extirpated the tumor under general anesthesia. Cystic tumor was seen continuously in the inferior alveolar nerve. Immunohistologically, the tumor cells were positive for Glut-1, weakly positive for EMA, and weakly positive for Claudin-1, and the histopathological diagnosis was INPN. In addition, absence of the BCR region of chromosome 22 and expression of the BCR-ABL fusion gene were observed by fluorescent in situ hybridization (FISH), and a chromosome 22 abnormality was confirmed. These findings indicated that the disease was a neoplastic lesion.

CONCLUSION

Expression of the BCR-ABL fusion gene in INPN that develops in the oral cavity is thought to be very rare, and to the best of our knowledge, ours is the first case to be reported in the literature. About three postoperative years have passed, but findings suggestive of recurrence have not been observed.

Neural and neurogenic tumours of the gastroenteropancreaticobiliary tract

Neural lesions occur uncommonly in the gastroenteropancreaticobiliary tract. However, due to the growing number of screening colonoscopy procedures, polypoid neural lesions of the colon are being recognised increasingly and range from benign tumours to high-grade malignant neoplasms. Morphological variability of neural tumours can be wide, although some entities share pathological features, and, as such, these lesions can be diagnostically challenging. We review the spectrum of pathology of neural tumours in the gastroenteropancreaticobiliary tract, with the goal of providing a practical approach for practising surgical pathologists.

Intraneural perineuriomas: diagnostic value of magnetic resonance neurography

Intraneural perineurioma (IP) is an under-recognized hypertrophic peripheral nerve tumor. It affects young patients involving frequently the sciatic nerve and its branches and presents with a progressive, painless and predominantly motor deficit. Magnetic resonance neurography (MRN) is a useful tool to localize the lesion, evaluate its extension, and discriminate between different etiologies. We reviewed the clinical records of 11 patients with pathologically confirm IP. Eight patients were males with mean age 19 years. Initial complains were unilateral steppage (seven patients), bilateral steppage (one patient), unilateral gastrocnemius wasting (one patient), unilateral thigh atrophy (one patient), and unilateral hand weakness (one patient). Nine patients had mild painless sensory loss. Examinations revealed involvement of sciatic nerve extending into the peroneal nerve (eight patients), posterior tibial nerve (one patient), radial nerve (one patient), and femoral nerve (one patient). MRN revealed enlargement of the affected nerve isointense on T1-weighted, hyperintense on T2 fat-saturated images, and with avid enhancement on post-contrast imaging. In all patients, a nerve biopsy confirmed the diagnosis. MRN allows early and non-invasive identification of this tumor and is a key tool providing localization and differential diagnosis in patients with slowly progressive focal neuropathies.

Anesthesia for a parturient with intraneural perineurioma: A case report

RATIONALE

Intraneural perineurioma is an extremely rare form of peripheral nerve sheath tumor; and the anesthetic management of a parturient with intraneural perineurioma, especially affecting spinal roots and nerves of extremities, is very rare.

PATIENT CONCERNS

A 28-year-old woman was referred to the hospital at 37+5 weeks' gestation, presenting with a 10-year history of paroxysmal acroanesthesia and aching with distal limbs.

DIAGNOSES

Based on the biopsy results, including immunohistochemical and electron microscopic findings, and molecular studies, her condition was diagnosed as intraneural perineurioma.

INTERVENTIONS

The size of pelvic nervous masses gradually increased with pregnancy. A scheduled elective cesarean section under general anesthesia was concluded for the patient under preoperative multidisciplinary consultation with anesthesiologist, neonatologist, and neurologist.

OUTCOMES

The patient and the neonate were discharged smoothly on the fourth postoperative day. During a 6-month follow-up period, no new neurologic complication was observed.

LESSONS

To our knowledge, this is the first case report that documented the anesthetic management for a parturient with intraneural perineuroma. Careful preconception care and multidisciplinary assessment are essential to achieve optimal reproductive outcomes.

Synovial Sarcoma of Peripheral Nerves: Analysis of 15 Cases

Synovial sarcoma of peripheral nerve (SSPN) is rare with only 26 cases reported in English. SSPN is often mistaken for a benign or malignant peripheral nerve sheath tumor (PNST) by clinicians and pathologists. Fifteen cases of SSPN were retrieved from the pathology files of 3 institutions. All tumors arose in a nerve based on imaging and/or operative findings and the diagnoses were histologically confirmed. Neuropathic symptoms predominated in 11 women and 4 men, 19- to 62-year-old (median, 39 years) with tumors involving the ulnar (5), median (3), peroneal (3) or sciatic (2) nerve, or the L4 or T1 nerve root (2). Tumor sizes ranged from 2 to 13 cm (median, 3.8 cm). The leading clinical diagnosis was PNST (9). Treatment was surgical (14) supplemented with radiation therapy (8) and chemotherapy (6). Fourteen tumors were monophasic and 1 was biphasic; 4 had poorly differentiated (PD) foci (1 rhabdoid). Diagnoses in 12 cases were verified by fluorescence in situ hybridization, reverse transcription polymerase chain reaction or both methods. Follow-up in 14 patients (median, 32 mo) revealed that 2/4 patients with PD tumors died with pulmonary metastases; another was alive with no current evidence of disease (NED) following 2 local recurrences, while the fourth had NED. In contrast, 9/10 patients without PD tumors were alive (7 NED) and 1 died at 12 months with pulmonary infiltrates. SSPN is under-recognized clinically and histologically as it mimics benign and malignant PNST. Molecular analysis is recommended to confirm the diagnosis. PD foci, including rhabdoid areas, may portend a worse outcome, similar to non-neural-based tumors.

Whorling cellular perineurioma: A previously undescribed variant closely mimicking monophasic fibrous synovial sarcoma

The authors present a distinctive perineurioma (PN) variant which morphologically strongly resembles monophasic fibrous synovial sarcoma (MSS). The patients were 3 males and 1 female. The age ranged from 15 to 61years (mean: 44years). Locations included the sole, lower jaw, palm and foot. The tumor size ranged from 1.3cm to 2.5cm in the largest dimension (mean 1.8cm). Morphologically, all tumors had an identical, monotonous appearance. The perineurial cells were closely packed and created a confluent cellular whorls and/or sheets in a scarce stroma, with only focally discernible long, slender cytoplasmic processes typical for perineurial differentiation. The nuclei were rounded or slightly elongated to tapered, without nuclear atypia. Mitoses were rare to completely absent. Atypical mitoses, hemorrhage, necrosis or calcifications were not present. The proliferative index (Ki-67) was 1-3%. All analyzed tumors were positive for EMA, Claudin-1, GLUT-1 and negative with S100 protein, CD34, OSCAR, CK7 and TLE-1. Two cases were tested by fluorescence in situ hybridization and neither showed alterations of the SYT gene. One case studied by electron microscopy showed characteristic features of perineurial differentiation. Follow-up was available for two patients both of which showed no evidence of disease at 8years and 6months, respectively. Based on their bland morphology, perineurial features and presumably benign clinical outcome we propose the term "whorling cellular perineurioma" for these tumors, which may represent an extremely cellular variant of sclerosing PN. Awareness of this PN subtype and its distinction from MSS is of utmost clinical significance.

Genomic analysis reveals frequent TRAF7 mutations in intraneural perineuriomas

Intraneural perineuriomas are benign peripheral nerve sheath tumors that cause progressive debilitating focal extremity weakness. The etiology of perineuriomas is largely unknown. We utilized whole exome sequencing, copy number algorithm evaluation, and high-resolution whole genome microarray to investigate for a genetic causal link to intraneural perineuriomas. Ten of 16 (60%) tumor cases had mutations in the WD40 domain of TRAF7, the same location for causal mutations of meningiomas. Two additional perineurioma cases had large chromosomal abnormalities in multiple chromosomes, including chromosome 22q. This study identifies a common cause for intraneural perineuriomas and an unexpected shared pathogenesis with intracranial meningiomas. Ann Neurol 2017;81:316-321.

Can Intraneural Perineuriomas Occur Intradurally? An Anatomic Perspective

BACKGROUND: Intraneural perineuriomas are rare, benign lesions produced by the neoplastic proliferation of perineurial cells. They typically present in adolescents and affect nerves of the limbs. In our experience, we have not encountered a single case of classic intraneural perineurioma at an intradural location.

OBJECTIVE: To determine whether intraneural perineuriomas could occur intradurally, given the prevalence of intradural nerve sheath tumors, and explain our findings with an anatomic perspective.

METHODS: We retrospectively reviewed the high-resolution magnetic resonance images of 56 patients from an institutional registry of patients with intraneural perineurioma. All cases were analyzed for signs of proximal extension toward spinal nerves, roots, and spinal cord. A literature review was performed. The clinical, radiological, and histopathological features of potential intradural lesions were critically appraised against strict criteria for a diagnosis of classic intraneural perineurioma.

RESULTS: Fifteen of 56 (27%) patients with intraneural perineurioma had a proximal localization in the lumbosacral or brachial plexus. Not a single case occurred proximal to the dorsal root ganglia (DRG). One case of trigeminal intraneural perineurioma occurred distal to the gasserian ganglion. A literature review did not reveal any convincing cases of classic intraneural perineuriomas occurring in an intraspinal intradural location and revealed only 1 possible case in an intracranial intradural location.

CONCLUSION: Based on our study, the occurrence of classic intraneural perineuriomas intradurally is exceedingly rare, if at all present. This may be related to the paucity of perineurial cells at the nerve root level and reciprocal interactions between neuroglial cells at the central-to-peripheral transition zones.

Pseudolipoblastic perineurioma: an unusual morphological variant of perineurioma that may simulate liposarcoma

Perineuriomas are rare peripheral nerve sheath tumors arising from or differentiating along the lines of normal perineurial cells. They can be divided into intraneural and soft tissue types, with the latter category including a significant number of morphological variants. Herein, we further expand their morphological spectrum to include "pseudolipoblastic" perineuriomas. These lesions occurred in the tongue of a 30-year-old man and in the triceps of a 67-year-old woman and were characterized by bland, epithelioid cells with striking intracytoplasmic vacuolization. The architecture varied, with some areas showing a striking "net-like" or "microreticular" pattern and smaller areas having a more typical spindled and whorled appearance. Clinical follow-up (5months and 52months, respectively) showed no evidence of local recurrence or metastasis. Multiple perineurial markers, including epithelial membrane antigen, claudin-1, GLUT-1, and collagen IV, were diffusely positive. Both cases were submitted in consultation out of concern that they represented high-grade liposarcomas. To the best of our knowledge, this unusual morphological variant of perineurioma has not been reported. These tumors appear to be entirely benign and should be cured with simple excision. Pseudolipoblastic perineuriomas should be distinguished from round cell and epithelioid pleomorphic liposarcomas, as well as from other tumors that may show prominent intracytoplasmic vacuolization.

Diagnosis and outcome of childhood perineurioma

INTRODUCTION

Intraneural perineurioma is a rare peripheral nerve tumor of childhood and early adulthood. Patients demonstrate progressive muscle weakness and atrophy largely without sensory complaints.

CASE

We report two children with perineurioma affecting the radial and femoral nerves. Electromyography (EMG), ultrasound, and 3-T MR imaging were important tools for localizing perineurioma and permitting its differentiation from other nerve lesions. The first patient underwent surgical excision of the perineurioma and a traditional nerve graft. At 10 months post-operative follow-up, she demonstrated no meaningful recovery of muscle strength compared to her pre-operative assessment. EMG did confirm axonal continuity indicating that reinnervation had occurred via the nerve graft. The second patient underwent a two-staged surgical procedure that included an end-to-side nerve transfer. At 18 months post-operative follow-up, she demonstrated mild improvement in muscle strength and EMG evidence of ongoing reinnervation.

CONCLUSION

The surgical management of perineurioma remains controversial, and reports of clinical recovery after nerve grafts and nerve transfers vary. Nerve transfers have been reported to provide superior results to traditional nerve grafting in adults with post-traumatic plexus injuries. The modest gain in strength of our patient who underwent a nerve transfer raises the question if this may also apply to patients with perineurioma. Additional studies will be required, which must also take into consideration that features of long-standing neuropathy (i.e., limb length discrepancy) have the potential to reduce the likelihood of reinnervation and clinical recovery.

‘Sclerosing’ Perineurioma: A Tumor Variant?

We describe two examples of soft tissue perineurioma, a hard tumor, 1.7 cm in diameter, involving the dermis and superficial subcutaneous tissue of the left thumb, and the other a massive, lobulated lesion of the pelvis. Both occurred in 49-year-old men. Both were mobile and well demarcated but unencapsulated. Their cut surfaces were white and collagenous. Microscopically, each consisted of spindle-shaped or epithelioid tumor cells in a dense stroma of haphazardly oriented collagen bundles. Spindle-shaped cells were individually distributed, whereas epithelioid cells were often arranged in cords or clusters. Cytologic atypia was conspicuous in the massive tumor, but no mitotic activity was observed. Immunostains showed diffuse reactivity for vimentin, membrane pattern staining for epithelial membrane antigen and type IV collagen, as well as patchy CD34 reactivity. Stains for S-100 protein, Leu-7, smooth muscle actin, desmin, and cytokeratin were negative. Ultrastructural studies showed perineurial cell characteristics, including slender cytoplasmic processes, numerous pinocytotic vesicles, occasional tight junctions, and discontinuous surface basement membrane. Perineuriomas featuring marked stromal sclerosis often occur in the hands of young adults, as has recently been reported; the authors considered it a clinicopathologic variant. Herein we report two sclerotic perineuriomas, one a small tumor of the thumb and the other a centrally situated, massive pelvic tumor with sclerosis and degenerative cytologic atypia. We believe that exaggerated collagen deposition in perineuriomas, occasionally associated with degenerative nuclear changes, is not a manifestation of a unique, clinically relevant tumor variant but rather a manifestation of chronicity akin to that seen in “ancient schwannoma” and ‘atypical neurofibroma.’

Case report: Intraneural perineurioma of the sciatic nerve in an adolescent - strategies for revealing the diagnosis

Diagnosis of intraneural conditions can be revealed by a combination of clinical examination, electrophysiology, magnetic resonance imaging (MRI), and targeted fascicular biopsy with subsequent microscopic analyses.

Multiple Perineuriomas in Chicken (Gallus gallus domesticus)

Intraneural perineurioma is an extremely rare condition characterized by perineurial cell proliferation within peripheral nerve (PN) sheaths. In the veterinary field, this entity has been reported only in a dog. We examined multiple enlargements of PNs in 11 chickens ( Gallus gallus domesticus) (9 Japanese bantams and 2 specific pathogen-free White Leghorn), which were inoculated with an avian leukosis virus (ALV) causing so-called fowl glioma. All chickens clinically exhibited progressive leg paralysis. Lumbosacral plexus, brachial plexus, and/or spinal ganglion were commonly affected, and these nerves contained a diffuse proliferation of spindle cells arranged concentrically in characteristic onion bulb-like structures surrounded by residual axons and myelin sheaths. The spindle cells were immunohistochemically negative for S-100α/β protein. Electron microscopy revealed that these cells were characterized by short bipolar cytoplasmic processes, occasional cytoplasmic pinocytotic vesicles, and discontinuous basal laminae. These features are consistent with those of intraneural perineurioma. Furthermore, the specific sequence of the ALV was detected in the PN lesions of 8/11 (73%) birds by polymerase chain reaction. These results indicate that the multiple intraneural perineuriomas of chicken may be associated with the ALV-A causing fowl glioma.

Canine Intraneural Perineurioma

A 6-year-old castrated German Shepherd Dog was presented with a 6-month history of progressive, nonpainful, left pelvic limb paresis. Magnetic resonance imaging revealed atrophy of left-sided epaxial and hypaxial muscles from L5–L7 and an enlarged L5 spinal nerve. Exploratory hemi-laminectomy revealed focally and cylindrically thickened L5 and L6 nerve roots. Histologic evaluation of a surgical biopsy specimen from the L6 dorsal nerve root, and the L5 nerve roots after later amputation revealed distended hypercellular fascicles. This distension was due to widely separated axons surrounded by concentric lamellations formed by neoplastic perineurial cells and their processes. These pseudo-onion bulbs were separated from each other by a basophilic myxoid stroma. The perineurioma cell processes were immunonegative for S-100 (a and b chains) and collagen IV, but were immunoreactive for laminin. The central axons were also immunoreactive for NF-200 and S-100. The proliferative index of the perineurioma cells, as determined by MIB-1 immunoreactivity, was about 3%. Ultrastructurally, the widely separated, interdigitating perineurioma cell processes were connected by desmosomal-like junctional complexes to form continuous circles. Their processes were covered by a discontinuous basal lamina. Each centrally placed axon was normally, thinly, or completely unmyelinated and was surrounded by a normal Schwann cell. These morphologic and immunologic features distinguish this lesion from hypertrophic neuropathy and were consistent with intraneural perineurioma.

Intraoral Pseudo-Onion Bulb Intraneural Proliferations in a Patient with Hemimandibular Hyperplasia: A Case Report and Review of the Literature

This report and review of the literature describes a case of benign intraoral lesions of perineurial origin in a patient with symptomatic hemimandibular hyperplasia causing partial denture soreness. Perineuriomas are a benign peripheral nerve sheath tumor composed of perineurial cells. Intraoral perineuriomas are an extremely rare entity. Two main types of perineuriomas have been described: intraneural and extraneural perineuriomas. A third, similar entity, called an intraneural pseudoperineuriomatous proliferation, has recently been proposed in the literature as a separate and distinctive diagnosis. This report describes the histologic and clinical presentation of intraneural pseudoperineuriomatous proliferations in a patient with hemimandibular hyperplasia.

MRI of intraneural perineurioma of the brachial plexus

Intraneural perineurioma is an uncommon benign tumor of the perineurium of peripheral nerve sheaths occurring primarily in adolescents or young adults. MRI is a valuable tool in suggesting this diagnosis and in surgical planning. We report an 18-year old female with progressive right-hand weakness, numbness, and severe atrophic changes of the hand secondary to an intraneural perineurioma involving the right brachial plexus, in whom the initial diagnosis was suggested by MRI.

[Nerve sheath tumours]

Peripheral nerve sheath tumors are common neoplasms in daily practice. Diagnosis and classification of most conventional peripheral nerve sheath tumors are relatively straightforward for the experienced observer; but on occasion, they are diagnostically challenging (especially with locally aggressive and malignant tumors). This article aims to provide an update of the data (clinical, histological, immunohistochemistry and genomic) of benign, intermediate and malignant peripheral nerve sheath tumors, thanks to the latest WHO "Classification of Tumors of Soft Tissue and Bone", published in 2013, which includes a new chapter on "Nerve Sheath Tumors". Advances in molecular biology have provided new insights into the nature of the various peripheral nerve sheath tumors, and have begun to suggest novel targeted therapeutic approaches.

Soft tissue perineurioma of the foot with 10q24 rearrangements: unique MRI features with histopathologic correlation

Perineurioma is an uncommon benign peripheral nerve sheath tumor with advanced perineurial differentiation. Two distinct subtypes are recognized: intraneural and soft tissue. We herein present a unique case of soft tissue perineurioma in the right foot of a 43-year-old man. Radiographs showed a non-specific soft tissue mass. On computed tomography scan, the mass was iso- to slightly hypodense relative to muscle. On T1- and T2-weighted images, the mass exhibited iso- to slightly low signal intensity relative to muscle with foci of high signal intensity. Slight contrast enhancement was noted on enhanced T1-weighted images with fat suppression. A marginal excision of the tumor was performed and histopathologic examination confirmed the diagnosis of soft tissue perineurioma. The clinicopathologic, radiologic, and cytogenetic findings are described, and the relevant literature is reviewed.

Myxoid perineurioma in a transplanted kidney

Perineuriomas are rare, benign peripheral nerve sheath tumors, most commonly found in the extremities and trunks. A handful of cases have been reported to arise from the retroperitoneum and in kidneys. To our knowledge, this is the first reported case of a myxoid perineurioma arising from a transplanted kidney. The patient is a 40-year-old Chinese male with end-stage kidney disease secondary to chronic sclerosing glomerulonephritis. He has a nonfunctioning renal graft in his right iliac fossa and a functioning graft in the left. Routine imaging found a mass in the nonfunctioning graft which was increasing in size. He underwent graft nephrectomy and histology revealed a myxoid perineurioma with no atypical features or malignancy.

Soft tissue perineurioma of the tongue: report of a case and review of the literature

Perineurioma is a rare benign tumor of the peripheral nervous system distinct from schwannomas and neurofibromas. It may be intraneural or extraneural (in the soft tissue). Extraneural soft tissue perineuriomas are uncommon; rare cases have been reported in the oral cavity. We present a case of soft tissue perineurioma in the tip of the tongue. The tumor was characterized by slender spindle cells, arranged in short fascicles or whorls, and focal areas showing a distinct storiform pattern. Tumor cells showed the immunohistochemical profile of perineurial cells, including epithelial membrane antigen. Smooth muscle actin, S-100, and CD34 were not expressed by the tumor cells. The tumor was surgically excised and in 2 years there has been no recurrence. Knowledge of the tumor in the oral cavity is important to reach a correct diagnosis and to avoid unnecessary aggressive local excision.

Intraneural perineurioma of unilateral radial and median nerves manifesting with long-standing focal amyotrophy in a 14-year-old-boy

Intraneural perineuriomas are rare tumors of the peripheral nerves with unique immunohistochemical findings. In this report, we highlight the clinical and imaging findings of an adolescent male with histologically proven intraneural perineurioma involving multiple nerves. The salient features included a clinically progressive course, imaging evidence of involvement of long segments of multiple nerves, enlargement of individual fascicles within the affected nerves, and intense contrast enhancement of the enlarged fascicles. The identification of enlarged fascicles with intense contrast enhancement within the affected and distended nerve segments may aid in distinguishing intraneural perineurioma from other tumors affecting the peripheral nerves.