Major-nerve schwannomas versus intramuscular schwannomas

Giant schwannoma on the lower leg: A case report and review of the literature

INTRODUCTION AND IMPORTANCE

Peripheral nerve sheath tumors are common neoplasm with different biological features ranging from benign to malignant. The majority of these tumors are smaller than 5 cm, whereas those larger are termed giant schwannomas. When localized in the lower legs, the maximum length of the schwannoma is less than 10 cm. We report a case of giant schwannoma of the leg and its management.

CASE PRESENTATION

A 11-year-old boy presented with a 13 cm × 5 cm firm, smooth, well-defined margin mass in the posterior-medial aspect of right leg. The tumor was fusiform, well capsulated, multi-lobulated soft tissue with 13 cm × 4 cm × 3 cm in size at the biggest region. On MRI the tumor was low signal, isointense with adjacent tissue on T1S, hyper-intense on T2-FS sequences and surrounded by a thin fat-like intense rim. Biopsy findings were considered most consistent with Schwannoma (Antoni A). Tumor resection was performed. The mass appeared capsulated, white, and glistening with 132 mm × 45 mm × 34 mm in size. Postoperative course was uneventful without neurological deficit.

CLINICAL DISCUSSION AND CONCLUSION

Schwannomas are the most common peripheral nerve sheath tumors that derived almost entirely from Schwann cells. Schwannomas usually affect the head and neck region, localization in the lower extremity is rare. When located in lower extremity, the maximum diameter of 5 cm is described in most studies. Clinical presentation of schwannomas is unclear and unspecific. Diagnosis is based on ultrasound, MRI, and histology. The recommended treatment for schwannoma is surgical enucleation or resection without damaging the involved nerve.

Magnetic Resonance Imaging of Nerve Tumors

Nerve tumors are uncommon soft tissue neoplasms predominantly arising from peripheral nerve sheath and Schwann cells. We review the manifestations of benign peripheral nerve sheath tumors, concentrating on distinguishing imaging features of schwannomas versus neurofibromas with an emphasis on treatment implications. Nevertheless, there is often an overlap between the imaging presentation of these two conditions, making the accurate radiologic diagnosis challenging. Therefore, tissue sampling is often needed for a definitive histologic diagnosis. Treatment planning largely depends on symptoms, location of the lesion, and underlying risk factors. Three major syndromes, neurofibromatosis type 1, type 2, and schwannomatosis, predispose patients to peripheral nerve sheath tumors (PNSTs), with particular concern about the malignant subtype expression. In patients with suspected PNSTs, correlation of imaging findings with clinical findings and genetic tests is helpful for a more accurate diagnosis and disease management. Some imaging features on magnetic resonance imaging and fluorodeoxyglucose-positron emission tomography can be helpful to differentiate malignant from benign subtypes.

Schwannoma in the extremity: clinical features and microscopic intra-capsular enucleation

Objective: Schwannomas are the most common type of neoplasm of the peripheral nerves. Enucleation is a standard surgical procedure; however, it occasionally results in iatrogenic nerve injury, even with atraumatic procedures. Herein, we present the clinical characteristics of schwannoma arising in the extremities and discuss the clinical outcomes of extra- and intra-capsular enucleation.

Patients and Methods: We reviewed 122 schwannomas treated at our institute. Schwannomas arising from the minor nerve (n=30) or intramuscularly (n=15) were operated using the extra-capsular technique. Of the 77 major nerve schwannomas, 62 schwannomas were treated using the intra-capsular technique and 15 schwannomas using the extra-capsular technique.

Results: Neurological deficits following enucleation were significantly lower using the intra-capsular technique than with the extra-capsular technique. The patient age, duration of symptoms, maximum tumor diameter, and site of occurrence were not associated with subsequent neurological deficits. With both techniques, no tumor recurrence was observed at the final follow-up.

Conclusion: These results support the use of intra-capsular micro-enucleation as a safe and reliable treatment for every type of schwannoma. To minimize the risk of nerve injury, en bloc resection should not be used because the main purpose of schwannoma surgery is the relief of symptoms, not tumor resection.

Morphology of the entering and exiting nerve as a differentiating feature of benign from malignant peripheral nerve sheath tumours of the brachial plexus

OBJECTIVE

To identify if morphology of the entering and exiting nerve involved by a nerve sheath tumour in the brachial plexus can help differentiate between benign (B) and malignant (M) peripheral nerve sheath tumours (PNSTs).

MATERIALS AND METHODS

Retrospective review of 85 patients with histologically confirmed primary PNSTs of the brachial plexus over a 12.5-year period. Clinical data and all available MRI studies were independently evaluated by 2 consultant musculoskeletal radiologists blinded to the final histopathological diagnosis assessing for maximal lesion dimension, visibility and morphology of the entering and exiting nerve, and other well-documented features of PNSTs.

RESULTS

The study included 47 males and 38 females with mean age 46.7 years (range, 8-81 years). There were 73 BPNSTs and 12 MPNSTs. The entering nerve was not identified in 5 (7%), was normal in 17 (23%), was tapered in 38 (52%) and showed lobular enlargement in 13 (18%) BPNSTs compared with 0 (0%), 0 (0%), 2 (17%) and 10 (83%) MPNSTs respectively. The exiting nerve was not identified in 5 (7%), was normal in 20 (27%), was tapered in 42 (58%) and showed lobular enlargement in 6 (8%) BPNSTs compared with 4 (33%), 0 (0%), 2 (17%) and 6 (50%) MPNSTs respectively. Increasing tumour size, entering and exiting nerve morphology and suspected MRI diagnosis were statistically significant differentiators between BPNST and MPNST (p < 0.001). IOC for nerve status was poor to fair but improved to good if normal/tapered appearance were considered together with improved specificity of 81-91% for BPNST and sensitivity of 75-83%.

CONCLUSIONS

Morphology of the adjacent nerve is a useful additional MRI feature for distinguishing BPNST from MPNST of the brachial plexus.

Intramuscular ancient schwannoma of the axillary nerve

We present the case of an adolescent with an intramuscular ancient schwannoma of the axillary nerve which, to the best of our knowledge, has not been reported before. Due to its deep location, intramuscular schwannoma has less clinical signs and hence, is difficult to diagnose. Ancient schwannoma, characterised by degeneration due to long course, is rare and can be mistaken for malignancy due to heterogeneous intensity and degeneration evident on MRI and nuclear atypia on histopathology. It is important to differentiate it from malignancy based on a clinically benign swelling with a long history, well-encapsulated mass on MRI with the split fat sign and absence of significant mitotic activity despite nuclear atypia. The aim of surgery should be enucleation of the tumour while preserving the function of the parent nerve.

The safety of primary surgical excision of small deep indeterminate musculoskeletal soft tissue masses

OBJECTIVE

To determine the suitability of primary excision of small indeterminate deep soft tissue masses presenting to a tertiary musculoskeletal oncology service.

METHODS AND MATERIALS

Review of all patients referred to a specialist musculoskeletal oncology service over a 20-month period with a deep indeterminate soft tissue mass by non-contrast MRI criteria that was recommended for primary surgical excision due to relatively small size (<30 mm). Data collected included age, gender, site and maximal size of the lesion, and final histological diagnosis for excised lesions.

RESULTS

85 patients were included, mean lesion size being 12 mm (range 5-29 mm). Primary surgical resection had been undertaken in 69 cases (81.2%) by the conclusion of data collection, 36 males and 33 females with mean age of 45.6 years (range 11-80 years). Of these, 11 cases (15.9%) were non-neoplastic, 53 (76.8%) were benign, 1 (1.4%) was intermediate grade, while 4 (5.8%) were malignant including 3 synovial sarcomas. Two of these were treated with re-excision of the tumour bed showing no residual disease, with no evidence of local recurrence at a mean of 10.7 months post-excision.

CONCLUSION

Primary surgical excision of small deep soft tissue masses that are indeterminate by non-contrast MRI criteria is considered a safe procedure when undertaken in a specialist musculoskeletal oncology service, with only 4 of 69 cases (5.8%) being malignant.

ADVANCES IN KNOWLEDGE

Small indeterminate deep soft tissue masses can safely be treated with primary excision in the setting of a specialist musculoskeletal oncology service.

Schwannomas of Uncommon Peripheral Locations: Analysis of Imaging Findings of 21 Cases

BACKGROUND

Schwannomas are benign slow-growing tumors most often associated with the cranial nerves. Schwannomas often originate from the eighth cranial nerve. They may also originate from the peripheral nervous system of the neck and extremities. However extracranial peripheral schwannomas are considered a rare entity.

OBJECTIVES

The knowledge of rare localizations and typical imaging findings will lead to a successfulradiological diagnosis. Therefore, in this study, we present the clinical findings and MRI characteristics of schwannomas with a rare localization involving the peripheral, lower and upper extremity and intramuscular regions.

MATERIALS AND METHODS

The hospital database was screened for patients with an extracranial soft tissue mass. Twenty-one cases of schwannomas were found in rare localization. We analyzed the MR images of these patients retrospectively. The MR images were evaluated in terms of tumor location, signal intensity, and enhancement pattern. The histological examination of all the patients confirmed the diagnosis of schwannoma.

RESULTS

In 21 patients, the schwannomas were peripheral, localized to upper (n = 6) and lower extremities (n = 11). The remaining four patients had intramuscular schwannomas. The patients diagnosed with intramuscular schwannomas had schwannomas in sternocleidomastoid, gastrocnemius, triceps muscle and lateral wall of the abdomen. The average long-axis diameter of the tumor was 27.7 mm and the average short-axis diameter was 16.4 mm. The contrast pattern was diffused in eight tumors and peripheral in 13.

CONCLUSION

In this study, we present clinical findings and MRI characteristics of schwannomas with a rare localization involving the peripheral, lower and upper extremity and intramuscular regions.

Intramuscular peripheral nerve sheath tumors: schwannoma, ancient schwannoma, and neurofibroma

PURPOSE

To analyze the prevalence of classic magnetic resonance imaging (MRI) findings of intramuscular peripheral nerve sheath tumors (PNSTs), including schwannoma, ancient schwannoma, and neurofibroma.

METHOD

Thirty pathologically confirmed benign intramuscular PNSTs (24 schwannomas, 3 ancient schwannomas, and 3 neurofibromas) were retrospectively reviewed. Classic MRI findings of PNSTs including split fat sign, fascicular sign, target sign, entering and exiting nerve, and thin hyperintense rim were assessed for each intramuscular PNST. Denervation change of the affected muscle was also assessed. In ancient schwannoma and neurofibroma, the signal intensity (SI) and enhancement pattern were analyzed.

RESULTS

All intramuscular schwannomas revealed two more classic MRI findings. Eight of the 24 intramuscular schwannomas revealed affected muscle denervation change. All intramuscular ancient schwannomas showed only split fat sign. All intramuscular ancient schwannomas showed denervation change of the associated muscle. All intramuscular neurofibroma showed split fat sign and one case with target sign was detected. Ancient schwannomas were isointense SI on T1-weighted image (T1WI) and one case had hyperintense foci. They showed heterogeneously hyperintense SI on T2-weighted image (T2WI) with heterogeneous enhancement. Neurofibromas were isointense SI (2/3) and slight hyperintense SI (1/3) on T1WI and heterogeneously hyperintense SI on T2WI with heterogeneous enhancement. One ancient schwannoma showed conglomerated calcifications.

CONCLUSIONS

Intramuscular schwannomas were easily diagnosed based on MRI. In the case of intramuscular ancient schwannoma and neurofibroma with only split fat sign among the classic MRI findings, they might be distinguished from other intramuscular soft tissue tumors based on muscle denervation change or typical crescent split fat sign.

Characterization of small, deeply located soft-tissue tumors: Conventional magnetic resonance imaging features and apparent diffusion coefficient for differentiation between non-malignancy and malignancy

OBJECTIVES

To compare magnetic resonance imaging (MRI) parameters of small, deeply located non-malignant and malignant soft-tissue tumors (STTs).

METHODS

Between May 2011 and December 2017, 95 MRIs in 95 patients with pathologically proven STTs of small size (<5 cm) and deep location (66 non-malignant and 29 malignant) were identified. For qualitative parameters, consensus reading was performed by three radiologists for presence of necrosis, infiltration, lobulation, and the tail sign. Apparent diffusion coefficient (ADC) was analyzed by two other radiologists independently. Univariable and multivariable analyses were performed to determine the diagnostic performances of MRI parameters in differentiating non-malignancy and malignancy, and for non-myxoid, non-hemosiderin STTs and myxoid STTs as subgroups. Interobserver agreement for ADC measurement was calculated with the intraclass correlation coefficient.

RESULTS

Interobserver agreement on ADC measurement was almost perfect. On univariable analysis, the malignant group showed a significantly larger size, lower ADC, and higher incidence of all qualitative MRI parameters for all STTs. Size (p = 0.012, odds ratio [OR] 2.57), ADC (p = 0.041, OR 3.85), and the tail sign (p = 0.009, OR 6.47) were independently significant on multivariable analysis. For non-myxoid, non-hemosiderin STTs, age, size, ADC, frequency of infiltration, lobulation, and the tail sign showed significant differences between non-malignancy and malignancy on univariable analysis. Only ADC (p = 0.032, OR 142.86) retained its independence on multivariable analysis. For myxoid STTs, only size and tail sign were significant on univariable analysis without independent significance.

CONCLUSIONS

Size, ADC, and incidence of qualitative MRI parameters were significantly different between small, deeply located non-malignant and malignant STTs. Only ADC was independently significant for both overall analysis and the non-myxoid, non-hemosiderin subgroup.

Benign peripheral nerve sheath tumor of digit versus major-nerve: Comparison of MRI findings

Objective

To compare the symptoms and magnetic resonance imaging (MRI) findings between digital peripheral nerve sheath tumor (PNST) and major-nerve PNST.

Methods

A total 36 cases with benign PNSTs (16 digital, 20 major-nerve) were enrolled. Chief complaint and Tinel sign were reviewed. Five classic MRI features of PNST, the signal intensity (SI), the enhancement, and the shape of tumor were evaluated on MRI.

Results

Half of each group showed tenderness. Tinel sign was less frequent in digital PNST (12.5%) than major-nerve PNST (95.0%, P < 0.001). Split fat sign, entering and exiting nerve, target sign, and thin hyperintense rim were only observed in major-nerve PNST (P = <0.001, <0.001, 0.492, and 0.002, respectively). Fascicular sign was found in digital PNSTs (31.3%), but more frequent in major-nerve PNST (P < 0.001). In digital PNSTs, mild hyperintense SIs (56.2%) on T1-weighted images (T1-WI) was noted, but none in major-nerve PNST (P < 0.001). Both groups showed hyperintense SIs on T2-WI (P = 0.371). Homogeneity on T2-WI was noted in 43.8% of digital PNSTs, but none in major-nerve PNSTs (P = 0.004). Both groups showed heterogeneous enhancement (P = 0.066), but four (25%) digital PNSTs showed homogeneous enhancement. Lobulated shape was noted in 50% of digital PNSTs but none of major-nerve PNSTs (P = 0.001). Digital nerve was involved at 81.3% of digital PNSTs. Three foot cases showed unusual manifestations: bone destruction, skin thickening, and subungual location.

Conclusion

In digital PNSTs, Tinel sign is not commonly found and classic MRI findings is insufficient. In addition, some digital PNSTs show different SI and enhancement from major-nerve PNSTs. However, digital soft tissue tumor involving digital neurovascular bundle and especially representing a fascicular sign should be considered the possibility of a digital PNST.

Differential Diagnosis of Intramuscular Schwannoma of the Craniocervical Region

Schwannomas in the head and neck are a relatively common condition. However, intramuscular schwannomas in the craniocervical region are extremely rare. The preoperative consideration of schwannomas is very important to preserve adjacent circulation and nerve function during the surgery in this area. Moreover, the treatment and preoperative evaluation of this condition is not firmly established in the past literatures. The authors successfully managed the intramuscular schwannoma in the craniocervical region, and provide the differential diagnoses with appropriate treatments.

Fatty rind of intramuscular soft-tissue tumors of the extremity: is it different from the split fat sign?

OBJECTIVE

To analyze intramuscular soft-tissue tumors with fatty rind, and to evaluate the difference between fatty rind and split fat sign on magnetic resonance imaging (MRI).

MATERIALS AND METHODS

We retrospectively analyzed 50 pathologically confirmed intramuscular masses on MRI. We evaluated the distribution and shape of fatty rind and muscle atrophy.

RESULTS

Fatty rind was found more frequently in benign lesions (80% [36 out of 45]) compared with malignant lesions (25% [1 out of 5]; P = 0.013). Thirty-six benign lesions were peripheral nerve sheath tumors (PNSTs; n = 19), hemangiomas (n = 11), myxomas (n = 2), ganglion cysts (n = 2), giant cell tumor (n = 1), and leiomyoma (n = 1). One malignant lesion was a low-grade fibromyxoid sarcoma. In all masses with fatty rind, fat was confined to the proximal and the distal ends. In 12 cases, complete or partial circumferential fatty rind was also noted. Fatty rinds at both ends showed crescent, triangular, or combined shape. The prevalence of crescent-shaped fatty rind was significantly higher in benign PNST (17 out of 38) compared with the other tumors (1 out of 32; P < 0.001). Complete circumferential fat was noted only in hemangioma (n = 5). Triangular fatty rind was related to peripheral location of the mass or muscle atrophy.

CONCLUSION

Most intramuscular tumors with fatty rinds were benign, and PNST was the most common tumor type. Fatty rind could be caused by displaced neurovascular bundle fat, fatty atrophy of the muscle involved, or intermuscular or perimysial fat. Crescent-shaped fatty rind was noted more frequently in benign PNSTs.

Intramuscular schwannoma: clinical and magnetic resonance imaging features

INTRODUCTION

Schwannomas that arise within the muscle plane are called intramuscular schwannomas. The low incidence of these tumours and the lack of specific clinical features make preoperative diagnosis difficult. Herein, we report our experience with intramuscular schwannomas. We present details of the clinical presentation, radiological diagnosis and management of these tumours.

METHODS

Between January 2011 and December 2013, 29 patients were diagnosed and treated for histologically proven schwannoma at the National University Hospital, Singapore. Among these 29 patients, eight (five male, three female) had intramuscular schwannomas.

RESULTS

The mean age of the eight patients was 40 (range 27-57) years. The most common presenting feature was a palpable mass. The mean interval between surgical treatment and the onset of clinical symptoms was 17.1 (range 4-72) months. Six of the eight tumours (75.0%) were located in the lower limb, while 2 (25.0%) were located in the upper limb. None of the patients had any preoperative neurological deficits. Tinel's sign was present in one patient. Magnetic resonance (MR) imaging showed that the findings of split-fat sign, low signal margin and fascicular sign were present in all patients. The entry and exit sign was observed in 4 (50.0%) patients, a hyperintense rim was observed in 7 (87.5%) patients and the target sign was observed in 5 (62.5%) patients. All patients underwent microsurgical excision of the tumour and none developed any postoperative neurological deficits.

CONCLUSION

Intramuscular schwannomas demonstrate the findings of split-fat sign, low signal margin and fascicular sign on MR imaging. These findings are useful for the radiological diagnosis of intramuscular schwannoma.

Points to notice during the diagnosis of soft tissue tumors according to the "Clinical Practice Guideline on the Diagnosis and Treatment of Soft Tissue Tumors"

To adequately treat soft tissue tumors, an accurate initial diagnosis is essential. In this article, we describe the notable points during initial diagnoses as outlined by the "Clinical Practice Guideline on the Diagnosis and Treatment of Soft Tissue Tumors". Clinical findings including pain and tumor size, growth speed, and depth, may be important in the diagnosis. In general, malignant soft tissue tumors tend to be larger than 5 cm in size, to occur in deep layers, and grow quickly. However, there are many exceptions. Magnetic resonance images can show characteristics of soft tissue tumors, but most of these are non-specific. The most reliable diagnostic procedure is histological examination. Therefore, a biopsy is mandatory. A core needle biopsy can be performed under local anesthesia at an outpatient clinic without the need for imaging guidance. In cases with deep-seated tumors, an image-guided biopsy is recommended. Incisional biopsies are also widely used procedures. In an incisional biopsy, the skin incision should be parallel to the long axis of the extremities. A meticulous hemostasis must be carried out to prevent post-biopsy hemorrhaging. If adequate hemostasis cannot be achieved, a drain is placed within the incision or at the closest possible site along the incision. Indications for an excisional biopsy are limited to superficial soft tissue tumors, less than 3 cm in size, located at a suitable distance from the nearest vital structure. Furthermore, an excisional biopsy should only be carried out after imaging studies are complete.

Erector Spinal Muscular Schwannoma of the Dorsal Ramus Nerve: A Case Report

We present a rare case of intramuscular schwannoma originating from the dorsal ramus nerve in a 62-year-old woman. The mass grew slowly, with pain developing upon touch five years prior. No neurological deficit was detected. The mass was observed in the erector spinae muscles in magnetic resonance imaging (MRI), and surgical excision was performed. The mass was well encapsulated with clear margin. The lesion appeared to originate from the cranial side. We completely removed the mass including the origin. Histopathology confirmed a schwannoma diagnosis. This is the first report, to our knowledge, of a dorsal ramus-nerve schwannoma within the erector spinae muscles.

Therapeutic effect and risk factors for complications of excision in 76 patients with schwannoma

BACKGROUND

Benign schwannoma is the most common tumor of peripheral nerves. However, the clinical course of excision and risk factors associated with postoperative neurological deficits are not well known. We evaluated the incidence of preoperative symptoms, the incidence of postoperative neurological deficits, and the risk factors of neurological deficits.

METHODS

We retrospectively reviewed data of 76 patients with schwannomas treated at our institution. We reviewed the clinical characteristics, and postoperative results, and determined the possible risk factors influencing the development of complications.

RESULTS

Excision of schwannoma improved the Tinel-like signs in 47 of 51 patients and spontaneous pain in 14 of 15. Eleven of 17 patients with sensory deficits showed complete recovery, but six continued to show deficits with or without improvement. Motor deficits that were observed in four patients persisted in one. New neurological deficits developed in 21 patients and persisted until final follow-up in 8. Tinel-like signs was the risk factor of surgery-related neurological deficits (p = 0.009).

CONCLUSIONS

New deficits developed predominantly in patients with preoperative Tinel-like signs. Attention should be given to patients with the factor.

Imaging findings of benign peripheral nerve sheath tumor in jaw

OBJECTIVE

The aim of this study was to investigate the imaging characteristics of peripheral nerve sheath tumors (PNSTs) in the jaw.

STUDY DESIGN

Imaging studies of 6 patients were retrospectively reviewed. Conventional radiography, computed tomography, and magnetic resonance imaging were performed in all patients.

RESULTS

A fusiform lesion continuous with the nerve was observed in 2 cases, with the tumor arising within the inferior alveolar canal. In the other 4 cases, with the tumor arising outside the canal, the tumor had protruded and eroded into the bone. Protrusion was also present in 1 of the 2 cases, with the tumor arising within the canal. A target or fascicular sign was observed each in 1 case.

CONCLUSIONS

A fusiform lesion continuous with the nerve and a target or fascicular sign was only present in a few cases. The PNSTs, however, showed a tendency to protrude into the bone.

Intramuscular schwannoma of the musculocutaneous nerve: An uncommon clinical presentation

A schwannoma is a benign peripheral nerve sheath tumor composed exclusively of Schwann cells. A major-nerve schwannoma with an intramuscular location is an extremely rare condition. We present a rare case of intramuscular schwannoma originating from the musculocutaneous nerve in a 71-year-old female. The patient presented with a 7-month history of a slowly growing, painless mass in the medial aspect of the proximal upper arm. Magnetic resonance imaging revealed an oval-shaped intramuscular soft tissue mass with iso-signal intensity relative to skeletal muscle on T1-weighted images and high signal intensity on T2-weighted images. A rim of fat surrounding the mass, suggesting the split-fat sign, was also observed. The tumor was completely enucleated using an intracapsular technique. Histological examination confirmed the diagnosis of schwannoma consisting of Antoni A and B areas. There was no immediate neurological deficit following surgery. The patient had no evidence of local recurrence and no neurological deficit at final follow-up. To the best of our knowledge, this is the first report of musculocutaneous nerve schwannoma within the coracobrachialis muscle.