Cerebellopontine angle schwannomas arising from the intermediate nerve: a scoping review

Neurosurgical Review - Intermediate nerve schwannomas (INS) are extremely rare lesions in literature. They have been described mimicking facial nerve schwannomas, but not vestibular schwannomas...     

Two Cases of Subfrontal Schwannoma,Including a Rare Case Located between the Endosteal and Meningeal Layers of the Dura

Subfrontal schwannomas arising from the olfactory groove are rare and their origin remains uncertain because olfactory bulbs do not possess Schwann cells. We present two cases of subfrontal schwannomas treated with surgical resection. In one case, the tumor was located between the endosteal and meningeal layers of the dura mater. This rare case suggests that subfrontal schwannomas may originate from the fila olfactoria.     

Schwannoma of the obturator nerve with urologic manifestations: report of a case

Peripheral nerve tumors, which are called schwannomas because they arise from nerve sheath Schwann cells, are rare tumors than can develop at any site in the body but involve the limbs in over 50% of cases. Only 13% of schwannomas arise in the trunk; about 3% of schwannomas are retroperitoneal, and about 4% of retroperitoneal tumors are schwannomas. Pelvic schwannomas are equally uncommon and can develop in a broad range of structures. The most common presenting manifestation is a very large space-occupying lesion responsible for compression of neighboring organs. Excision of the tumor is often extremely difficult or impossible. Although obturator nerve schwannomas are exceedingly rare, their paravesical location is suggestive of he diagnosis. Computed tomography and magnetic resonance imaging are the most useful investigations, although they cannot determine the exact nature of the tumor. During surgery, every effort should be made to preserve the integrity of the nerve, although this is not always possible; obturator nerve injury does not seem associated with severe impairments.     

Malignant peripheral nerve sheath tumour of the trigeminal nerve: case report and literature review

Although all trigeminal nerve schwannomas are uncommon, malignant schwannomas are extraordinarily rare. We describe a patient who presented with clinical and radiological features of a trigeminal schwannoma; however, pathological analysis showed a malignant peripheral nerve sheath tumour (WHO Grade IV). We discuss these extremely rare tumours and their management.     

Malignant schwannoma of the trigeminal nerve

Malignant schwannomas are rare in the head and neck, even though benign schwannomas of this area are common. A case of a malignant schwannoma of the fifth cranial nerve with symptoms of otalgia and serous otitis media is described. About 20 such cases have been reported in the literature.     

Laparoscopic resection of schwannoma in the anomaly of obturator nerve

Most retroperitoneal schwannomas are benign tumors originating from schwann cells and are relatively rare, especially schwannomas arising in the obturator nerve. In this paper, we describe a 44-year-old woman with a retroperitoneal schwannoma in the anomaly of the obturator nerve, which was treated by laparoscopy without any complications.     

Facial Nerve Schwannoma of the Cerebellopontine Angle: A Diagnostic Challenge

Facial nerve schwannomas are rare lesions that may involve any segment of the facial nerve. Because of their rarity and the lack of a consistent clinical and radiological pattern, facial nerve schwannomas located at the cerebellopontine angle (CPA) and internal auditory canal (IAC) represent a diagnostic and therapeutic challenge for clinicians. In this report, a case of a CPA/IAC facial nerve schwannoma is presented. Contemporary diagnosis and management of this rare lesion are analyzed.     

Schwannomas of the falx

A case of multiple schwannomas arising from the falx in a 17-year-old girl, previously operated on for an intracerebral schwannoma, is presented. The appearance of multiple schwannomas has to be considered in the followup of the rare cases of intracranial schwannomas not related to cranial nerves.     

Intrathoracic multiple schwannomas of a single intercostal nerve

Intrathoracic schwannomas are solitary in general. We report a rare case of intrathoracic multiple schwannomas arising from a single intercostal nerve. A 27-year-old man was admitted with multiple tumors, along with the fourth intercostal nerve in the posterior chest wall. Thoracoscopic surgical exploration found a small tumor at 2 cm distal to the main tumors, which had not been detected preoperatively. All these tumors were completely resected en bloc and were diagnosed as schwannomas of the fourth intercostal nerve.     

Intramedullary melanotic schwannoma of the cervical spinal cord: report of a case

We present a case report of a patient with an intramedullary tumor of the midcervical cord. At surgery, the lesion was found to be highly pigmented, and pathological analysis revealed a melanotic schwannoma. Intramedullary schwannomas and melanotic schwannomas are exceedingly rare. This is the second reported case of an intramedullary melanotic schwannoma of the central nervous system.     

Glossopharyngeal schwannoma: review of five cases and the literature

Glossopharyngeal schwannomas are rare tumors in spite of the fact that acoustic schwannomas account for 8%-10% of intracranial tumors. There have been 23 reported cases in the literature. This report of five cases is the largest series of these tumors. The presentation, radiological workup, operation, and long-term postoperative results will be presented, along with a review of the literature.     

Epithelioid malignant peripheral nerve sheath tumor arising in a schwannoma, in a patient with "neuroblastoma-like" schwannomatosis and a novel germline SMARCB1 mutation

Epithelioid malignant peripheral nerve sheath tumors arising in preexisting schwannomas are extremely rare. We report an unusual example occurring in a patient with multiple schwannomas (schwannomatosis), all but 1 of which showed "neuroblastoma-like" histology. By immunohistochemistry, both the epithelioid malignant peripheral nerve sheath tumor and the schwannomas showed a complete loss of the Smarcb1 protein. Subsequent genetic evaluation revealed the presence of a novel germline mutation in the SMARCB1/INI1 gene in the patient and in 3 of her children, 2 of whom were diagnosed with atypical teratoid/rhabdoid tumors of the brain.     

Intrasellar schwannomas: report of two cases

OBJECTIVE AND IMPORTANCE: The complex regional anatomic features surrounding the sella turcica make the differential diagnosis of intrasellar and parasellar lesions complicated. Sellar and parasellar schwannomas are rare. With the exclusion of parasellar schwannomas arising from cranial nerves within the cavernous sinus and extending into the sella, there have been only two reported cases of true intrasellar schwannomas. CLINICAL PRESENTATION: We describe the clinical, radiological, and pathological features of two cases in which the histopathological diagnosis of schwannoma was confirmed with immunohistochemical analyses and/or electron microscopy. INTERVENTION: The two cases were grossly resected via a transsphenoidal approach. Follow-up monitoring revealed no evidence of recurrence. CONCLUSION: Schwannomas may atypically occur in the sellar region, in which they demonstrate the typical light microscopic, immunohistochemical, and ultrastructural features observed in the peripheral nervous system. New and existing hypotheses regarding the histopathogenesis of intrasellar and parasellar schwannomas are presented.     

A Case of Benign Schwannoma of the Ascending Colon Treated With Laparoscopic-Assisted Wedge Resection

Isolated colonic schwannomas are rare gastrointestinal mesenchymal tumors. Only a small number of cases have been reported. Occurrence of these tumors is more common in the stomach than in the large intestine. These spindle cell lesions are distinct from leiomyoma, leiomyosarcoma, and gastrointestinal stromal tumors because the tumor cells have a distinct immunophenotype, with strong diffuse positivity for S-100 and vimentin, as well as corroborative negative staining of CD117 and smooth muscle markers. We present a case of colonic schwannoma in a 70-year-old woman who had no specific symptoms. The patient was diagnosed with a submucosal tumor in the ascending colon on colonoscopy and abdominal computed tomography. Laparoscopic-assisted wedge resection of colon was performed. The very rare pathologic diagnosis of ascending schwannoma was made postoperatively. This case is interesting because schwannomas of the colon and rectum are extremely rare and are treated by laparoscopic-assisted wedge resection.     

Paraspinal plexiform schwannoma of unknown nerve origin: A case report

Introduction and importanceSchwannomas are benign, slow-growing nerve sheath tumors of neoplastic Schwann cells. They are the most common peripheral nerve tumors in adults and are typically discovered incidentally due to their asymptomatic presentation. Despite the fact that most schwannomas are unassociated with a syndrome, their etiology is thought to be related to alterations or loss of the neurofibromatosis type two tumor suppressor gene.Case presentationWe present the case of a fifteen-year-old female who presented with a recurrent lower back/upper buttocks 9 cm mass with imaging suspicious for schwannoma. Needle biopsy revealed an S100 positive cellular schwannoma with patchy Ki-67. During surgical dissection down to the sacrum, no nerve of origin was identified.Clinical discussionSchwannomas have no pathognomonic findings on MRI and may occur at any location that Schwann cells are present; therefore, confirming a diagnosis relies on histopathology. Plexiform schwannomas are defined by a “network-like” intraneural growth pattern and are exceedingly rare in paediatric populations. A location distinct from the spinal canal is also very rare as schwannomas typically originate from the head and neck region.ConclusionPaediatric plexiform schwannomas have been rarely reported. Surgical planning relies on multiple factors such as tumor size, tumor location, pathologic features and symptomatic burden. The distinctive features of this case including an unknown nerve origin and a location outside the spinal canal provide a unique opportunity to discuss the diagnosis and management of paraspinal schwannomas and the impact on operative planning when a nerve of origin is not identified.     

The controversial nosology of benign nerve sheath tumors: neurofilament protein staining demonstrates intratumoral axons in many sporadic schwannomas

Schwannomas are benign peripheral nerve sheath tumors believed to be composed purely of cells with ultrastructural features of Schwann cells; these tumors are believed to develop eccentrically from the surface of nerves and not to contain axons, other than immediately beneath the capsule. This concept has recently been disputed in cases associated with neurofibromatosis type 2. The usual presence of intratumoral axons in neurofibromas is said to allow easy distinction from schwannomas. Eighty sporadic schwannomas (20 conventional, 20 cellular, 20 ancient, 10 gastric, and 10 plexiform) were retrieved from the authors' files. Hematoxylin-and-eosin stained slides were reviewed, diagnoses were confirmed and all tumors were stained for S-100 protein and neurofilament protein (NFP). The amount (rare, focal, multifocal, and diffuse) and distribution (central and/or peripheral) of axons within the tumors were analyzed. All tumors were strongly and diffusely positive for S-100 protein (nuclear and cytoplasmic staining). NFP-positive axons were identified in 11 of 20 (55%) conventional schwannomas (2 rare, 4 focal, 3 multifocal, and 2 diffuse; 5 central, 4 peripheral, and 2 central and peripheral) and in 15 of 20 (75%) cellular schwannomas (3 rare, 6 focal, and 6 multifocal; 12 central, 1 peripheral, and 2 central and peripheral). Of the 20 ancient schwannomas, 7 cases (35%) showed intratumoral axons, highlighted by NFP immunostaining (1 rare, 4 focal, 1 multifocal, and 1 diffuse; 4 peripheral, 2 central, and 1 central and peripheral). Most cases of gastric schwannoma showed no evidence of intratumoral axons; 9 cases (90%) were negative for NFP and only 1 case (10%) was positive (focal and central). Seven of 10 cases (70%) of plexiform schwannomas were negative for NFP, whereas only 3 cases (30%) showed positive axons (2 multifocal and 1 focal; 3 central). The unexpected but quite frequent presence of intratumoral axons in schwannomas argues against conventional views of these lesions' pathogenesis as an eccentric encapsulated lesion and raises the possibility that a more diverse cell population, perhaps more closely resembling neurofibromas, may constitute these neoplasms. Although NFP-positive axons were most often present in the conventional and cellular variants of schwannoma, their presence was also observed in a minority of ancient, gastric and plexiform schwannomas. Differentiation between neurofibroma and schwannoma in cases with overlapping cytoarchitectural features should not be based solely on the presence or absence of NFP-positive axons within a given tumor.     

Supratentorial convexity leptomeningeal schwannoma: case report

OBJECTIVE AND IMPORTANCE: Leptomeningeal schwannomas are very rare; to our knowledge, only one case has been previously reported. The possible histogenesis and differential diagnosis of intracranial schwannomas not related to cranial nerves are discussed. CLINICAL PRESENTATION: A 53-year-old man presented with a sudden onset of seizures. Computed tomographic scans revealed a small hypodense mass in the peripheral aspect of the left frontal lobe. The mass was hypointense on T1-weighted and hyperintense on T2-weighted magnetic resonance imaging scans, with ring enhancement after contrast medium administration. INTERVENTION: A craniotomy was performed for total removal of the tumor, revealing a well-demarcated, firm, spherical tumor beneath the dura. The tumor was easily separated from the brain. Histologically, the tumor was observed to be within the subarachnoid space, intimately attached to the pia mater. The adjacent brain tissue and dura mater were free of tumor cells. The histological diagnosis was schwannoma. CONCLUSION: Computed tomographic and magnetic resonance imaging findings in our case were consistent with those for a schwannoma, although the subarachnoid space is an extremely rare location for schwannomas. We emphasize that schwannomas may arise in the subarachnoid space.     

Atypical invasion of the temporal bone in vestibular schwannoma

Vestibular schwannomas typically present with erosion of the temporal bone that is limited to the boundaries of the internal auditory canal. Four patients with extensive erosion, excavations, and pseudosatellite defects in the petrous apex are presented. These bony changes extended anteriorly up to the level of the carotid canal. The patients did not have stigmata of neurofibromatosis type 2 and they did not have systemic bony disorders. The tumors did not show any unusual histopathologic changes. Such invasive tumors present an unusual surgical challenge compared to vestibular schwannomas with a more typical pattern of bony erosion. Radiological features and surgical considerations relevant to vestibular schwannomas with this rare presentation are discussed.     

Atypical Invasion of the Temporal Bone in Vestibular Schwannoma

Vestibular schwannomas typically present with erosion of the temporal bone that is limited to the boundaries of the internal auditory canal. Four patients with extensive erosion, excavations, and pseudosatellite defects in the petrous apex are presented. These bony changes extended anteriorly up to the level of the carotid canal. The patients did not have stigmata of neurofibromatosis type 2 and they did not have systemic bony disorders. The tumors did not show any unusual histopathologic changes. Such invasive tumors present an unusual surgical challenge compared to vestibular schwannomas with a more typical pattern of bony erosion. Radiological features and surgical considerations relevant to vestibular schwannomas with this rare presentation are discussed.     

Intramedullary melanotic schwannoma of the cervicomedullary junction

We report a case of a patient with an intramedullary tumor of the cervicomedullary junction. At operation, the tumor was noted to be highly pigmented, and pathological study demonstrated that the tumor was a melanotic schwannoma. Both intramedullary schwannomas and melanotic schwannomas in any location in the body are exceedingly rare. This is the first reported case of an intramedullary melanotic schwannoma of the central nervous system. The possible origin of this tumor is discussed.