Vascularization of peripheral neurilemomas: angiographic, computed tomographic, and histologic studies

Sonographic Features and Diagnosis of Peripheral Schwannomas

BACKGROUND

To determine the sonographic features of peripheral schwannomas.

METHODS

This retrospective study included 54 cases of schwannoma in 51 patients. Ultrasonography (US) and MRI were performed in all patients. The US features of each tumor were analyzed and compared with pathologic findings. The US target sign was compared with the MRI findings.

RESULTS

On US, 53 of the 54 schwannomas had a regular shape and clear margins, and one had an irregular shape. Thirty-seven of the 54 schwannomas were categorized as solid, 16 as cystic and solid, and one as entirely cystic; distal sound enhancement was associated with 47 schwannomas. The target sign was seen in 24, the rat tail sign in 28, the vessel accompanying sign in 22, and the split fat sign in 5. The entering and exiting nerves were situated centrally in 9 and eccentrically in 19 schwannomas. Vascularity on color Doppler imaging using a 0 to III scale was graded 0 in 4 schwannomas, I in 10, II in 26, and III in 14. Twenty-four target signs were detected in 54 schwannomas by US, and 28 were detected by MRI. There was good agreement between the target signs noted on US and those seen on MRI (κ = 0.631, p < 0.001).

CONCLUSIONS

The sonographic diagnosis of peripheral schwannomas is feasible and reliable. The target sign is a prominent US feature in peripheral schwannomas, comparable to that observed with MRI. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:127-133, 2017.

Spectrum of superficial nerve-related tumor and tumor-like lesions: MRI features

Superficial soft-tissue masses arising from skin appendages, metastasis, and inflammatory lesions have been widely reported. However, nerve-related superficial mass-like lesions other than peripheral nerve sheath tumors are less commonly described. High resolution magnetic resonance imaging (MRI) is an excellent non-invasive tool for the evaluation of such lesions. In this article, the authors discuss the entire spectrum of these lesions and also outline a systemic diagnostic approach.

Misdiagnosis of retroperitoneal schwannoma: A retrospective study of 20 cases

AIM: To investigate the clinical features, diagnosis, treatment, and prognosis of retroperitoneal schwannomas.

METHODS: A total of 113 patients with retroperitoneal neoplasms treated at the Department of General Surgery of the First Hospital of China Medical University in the past decade, of whom 20 were diagnosed with retroperitoneal schwannoma. The clinical data for the 20 patients were retrospectively reviewed.

RESULTS: All the patients underwent radiological examination and surgical excision, and were confirmed with retroperitoneal schwannoma by pathology. Except that two cases undergoing enucleation and partial excision were lost to follow-up, all others (18/20) were evaluable. Among the 18 cases, 17 were treated by complete surgical resection, had high quality lives, and showed no evidence of recurrence during a mean follow-up of 40.5 mo (range 11 to 83 mo), and 1 underwent enucleation and had the same favorable prognosis during the 28-month follow-up.

CONCLUSION: Retroperitoneal schwannomas are rare and preoperative diagnosis is difficult. Radiologic findings cannot make an accurate diagnosis. Complete surgical excision should be considered. Patients undergoing complete surgical resection tend to do well without evidence of recurrence.

Imaging findings of neurogenic tumours in the head and neck region

OBJECTIVE

The aim of this study was to describe the CT, MRI and ultrasonography findings of five cases of neurogenic tumours in the head and neck region.

METHODS

Five neurogenic tumours were analysed with respect to their CT value, the presence of cystic change, target sign, lobulation, connection to the nerve and vascularity.

RESULTS

The contrast-enhanced CT (ECT) of the schwannomas demonstrated either a mass with low enhancement (two out of three cases), which reflected the predominant Antoni B components, or a mass with cystic changes, which was an Antoni A-based schwannoma displaying cystic changes (one out of three cases). On MRI, all tumours showed homogeneous and isointense signals for muscle on T₁ weighted images (T₁ WIs). T₂ weighted images (T₂ WIs) and gadolinium (Gd)-enhanced T₁ WIs demonstrated target sign in both schwannomas. Ultrasound examination showed a well-defined, ovoid or round hypoechoic mass. The direct connection to the nerve was demonstrated in two of the five cases. Lobulation was observed in only one of the five cases and cystic changes were observed in one of the five cases. In all of the cases, no vascularity was seen in power Doppler images (PDIs) obtained percutaneously.

CONCLUSIONS

Low-enhanced areas on ECTs can be specific for schwannomas, which suggests the predominance of Antoni B components. The target sign on T₂ WIs and Gd-enhanced T₁ WIs can be specific, which can be used to differentiate the two different components (Antoni A and Antoni B). The direct connection to the nerve can be a specific finding for neurogenic tumours; however, at present the sensitivity is 40%.

Pictorial essay: imaging of peripheral nerve sheath tumours

Peripheral nerve sheath tumours (PNST) may be benign or malignant. Benign PNSTs include neurofibroma and schwannoma. Neurogenic tumours share certain characteristic imaging features, suggested by a fusiform-shaped mass with tapered ends, the "split-fat" sign, atrophy of the muscles supplied by the involved nerve, the "fascicular sign," and the "target sign"; these imaging features are best demonstrated on magnetic resonance imaging. This pictorial essay emphasizes the characteristic signs and distinguishing features of PNSTs on imaging.

Gastric schwannomas: radiological features with endoscopic and pathological correlation

AIM

To describe the radiological, endoscopic, and pathological findings of gastric schwannomas in 16 patients.

MATERIALS AND METHODS

The radiological, endoscopic, and pathological findings of 16 surgically proven cases of gastric schwannoma were retrospectively reviewed. All patients underwent computed tomography (CT) and four patients were evaluated with upper gastrointestinal series. Two radiologists reviewed the CT and upper gastrointestinal series images by consensus with regard to tumour size, contour, margin, and growth pattern, the presence or absence of ulcer, cystic change, and the CT enhancement pattern. Endoscopy was performed in eight of these 16 patients. Six patients underwent endoscopic ultrasonography. Pathological specimens were obtained from and reviewed in all 16 patients. Immunohistochemistry was performed for c-kit, CD34, smooth muscle actin, and S-100 protein.

RESULTS

On radiographic examination, gastric schwannomas appeared as submucosal tumours with the CT features of well-demarcated, homogeneous, and uncommonly ulcerated masses. Endoscopy with endoscopic ultrasonography demonstrated homogeneous, submucosal masses contiguous with the muscularis propria in all six examined cases. On pathological examination, gastric schwannomas appeared as well-circumscribed and homogeneous tumours in the muscularis propria and consisted microscopically of interlacing bundles of spindle cells. Strong positivity for S-100 protein was demonstrated in all 16 cases on immunohistochemistry.

CONCLUSION

Gastric schwannomas appear as submucosal tumours of the stomach and have well-demarcated and homogeneous features on CT, endoscopic ultrasonography, and gross pathology. Immunohistochemistry consistently reveals positivity for S-100 protein in the tumours.

Retroperitoneal neurilemoma diagnosed by endosonographically guided fine needle aspiration

Retroperitoneal neurilemoma is an often asymptomatic benign tumor that is usually discovered incidentally. We report a case of retroperitoneal neurilemoma diagnosed via endosonographically guided fine needle aspiration and emphasize the importance of obtaining a definite diagnosis before surgical treatment.

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

Numerous neurogenic tumors can affect the musculoskeletal system, including traumatic neuroma, Morton neuroma, neural fibrolipoma, nerve sheath ganglion, neurilemoma, neurofibroma, and malignant peripheral nerve sheath tumors (PNSTs). The diagnosis of neurogenic tumors can be suggested from their imaging appearances, including lesion shape and intrinsic imaging characteristics. It is also important to establish lesion location along a typical nerve distribution (eg, plantar digital nerve in Morton neuroma, median nerve in neural fibrolipoma, large nerve trunk in benign and malignant PNSTs). Traumatic and Morton neuromas are commonly related to an amputation stump or are located in the intermetatarsal space, respectively. Neural fibrolipomas show fat interspersed between nerve fascicles and are often associated with macrodactyly. Nerve sheath ganglion has a cystic appearance and commonly occurs about the knee. Radiologic characteristics of neurilemoma, neurofibroma, and malignant PNST at computed tomography (CT), ultrasonography, and magnetic resonance imaging include fusiform shape, identification of entering and exiting nerve, low attenuation at CT, target sign, fascicular sign, split-fat sign, and associated muscle atrophy. Although differentiation of neurilemoma from neurofibroma and of benign from malignant PNST is problematic, recognition of the radiologic appearances of neurogenic tumors often allows prospective diagnosis and improves clinical management of patients.

Spectrum of neurogenic tumors in the thorax: CT and pathologic findings

Neurilemomas and neurofibromas appear as round soft tissue masses at CT. Variable enhancement with either homogeneity or heterogeneity is seen in neurilemomas. Attenuation of the tumors on enhanced CT depends on histology: the extent of Antoni A or B tissue and the amount of myxoid or cystic degeneration or hemorrhage. Neurofibromas are usually homogeneous low attenuation lesions on unenhanced CT. They show homogeneous enhancement or early central blush on enhanced scan. The extent of enhancement depends on the proportions of tumor components: nerve sheath cells, collagen bundles, and areas of myxoid degeneration. Malignant nerve sheath tumors show variable attenuation. Bony destruction, pleural effusion, and metastatic pulmonary nodules may also occur. Ganglioneuromas appear as oblong homogeneous low attenuation lesions on both enhanced and unenhanced CT. This low attenuation is due to their pathologic components, with an abundant amount of myxoid matrices and a relatively small amount of ganglion cells. Neuroblastomas appear as aggressive soft tissue lesions with calcification. Ganglioneuroblastomas may appear with features in between those of ganglioneuromas and neuroblastomas. The typical location of the posterior mediastinum or the aortopulmonary window and high enhancement with administration of contrast medium at CT suggest the diagnosis of paragangliomas.

Retroperitoneal ancient schwannoma: review of clinico-radiological features

A case is reported here of an ancient schwannoma in the retroperitoneum. The findings of abdominal ultrasound and CT in a patient with a retroperitoneal ancient schwannoma are presented, and the clinical and radiological features of this unusual tumour are reviewed. The presence of a large, well-delineated complex cystic mass in the deep soft tissues should raise the possibility of an ancient schwannoma. It is important to recognize these tumours as benign with excellent prognosis so as to avoid unnecessary radical surgery.

Pictorial review: imaging of peripheral nerve tumours

The ultrasound, computed tomography and magnetic resonance features of extracranial nerve tumours are reviewed. Characteristic locations and appearances help to define nerve tumours although the imaging findings of nerve and other soft tissue tumours overlap.

Case report 872. "Ancient" schwannoma (degenerated neurilemoma)

A case of an ancient schwannoma was presented. The rare occurrence of this tumor has resulted in only a few reported cases with descriptions of its features on imaging. Our patient's tumor, like one previously reported case, demonstrated calcification on the plain film - a finding not associated with other histologic types of schwannomas. Angiography revealed the tumor to be hypervascular. Evaluation by MRI demonstrated a lobulated, encapsulated soft tissue mass containing several cystic areas that corresponded histologically to areas of necrosis. Hypertrophied blood vessels were seen in the periphery of the tumoral mass. Too few ancient schwannomas have been reported to conclude whether or not radiographic evidence of soft tissue calcification is characteristic of this histologically distinctive subtype of schwannoma. However, since calcification is seen histologically as part of the degenerating process, its presence on plain films could be a feature of this tumor. Furthermore, the presence of cystic areas on MRI is not surprising given the pathological changes that occur in this tumor. We suggest that a diagnosis of ancient schwannoma be considered when a patient presents with a hypervascular soft tissue mass containing amorphous calcification on plain films and cystic areas on MRI. Despite the nonspecificity of these imaging findings, this point is relevant because each of these features suggests the presence of a malignant mass. Awareness of the possibility of a benign ancient schwannoma could obviate unnecessary radical surgery.

Benign retroperitoneal schwannoma

A rare case of benign retroperitoneal schwannoma in a 76-year-old man is reported. Ultrasound and computerized tomography disclosed two cystic retroperitoneal tumors sized 12 cm and 7 cm. The larger tumor was located anterior to psoas muscle and the smaller one was within the muscle. The larger tumor was excised via laparotomy. After 3.5 years follow-up the intramuscular tumor has remained unchanged and the patient has no symptoms.

A very large neurilemmoma of the anterior interosseous nerve

A very large neurilemmoma of more than 15 years duration, arising from the anterior interosseous nerve, is reported. To our knowledge, this is the largest ever described. While the symptoms and all other diagnostic findings suggested that the neurilemmoma originated from the median nerve, it needed angiography to provide the final diagnosis.

Preoperative diagnosis of soft tissue tumours

Over a period of 3 years in Southern Sweden 35 patients were seen with deep-seated limb sarcomas without metastases, 30 of whom were referred before any operation had been carried out. Thirty seven patients with deep-seated benign lesions were referred during the same period because of suspected malignancy. A preoperative diagnosis considered sufficient for a definitive operation was made from the clinical findings, aspiration cytology and radiographic examination, but without open biopsy, in 59 of these 67 cases. The differentiation between a benign and a malignant tumour was correct in all but one. The extent of excision necessary to achieve adequate margins for a soft-tissue sarcoma can often be reduced if open biopsy is avoided, with preservation of function. We conclude that treatment without open biopsy is possible in the great majority of patients with soft-tissue sarcoma.