Schwann cell-onion bulb tumor of the trigeminal nerve: hyperplasia, dysplasia or neoplasia?

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.

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.

Solitary localised hypertrophic neuropathy of the cauda equina

Localised hypertrophic neuropathy (LHN) is an uncommon non-neoplastic lesion, which is rare in the central nervous system. We report a patient with LHN of the cauda equina. Pre-operatively these lesions cannot be differentiated from schwannoma or other benign tumours or expansions of the nerve roots. Treatment is generally surgical, largely to confirm the diagnosis, and examination of the surgical specimen reveals an expansion of the nerve by "onion bulb" whorls of Schwann cells (S-100 positive). Multiple lesions may be associated with the generalised diffuse hypertrophic neuropathies or chronic inflammatory demyelinating polyneuropathies. It should be differentiated from intraneural perineuroma, which has a similar appearance but comprises perineural cells (epithelial membrane antigen positive). Adjuvant therapy is not required.

Intraneural perineurioma: a systematic review with illustrative cases

CONTEXT

Intraneural perineurioma may be confused with other "onion bulb" Schwann cell entities (localized hypertrophic neuropathy, reactive/demyelinating processes, or inherited polyneuropathies of Charcot-Marie-Tooth/Dejerine Sottas) due to similar clinical, radiologic, and histologic features. Perineurial and Schwann cells can only be differentiated by ultrastructure and immunohistochemsitry.

OBJECTIVE

To identify and summarize the clinicopathologic features of true cases of intraneural perineurioma from the English language literature.

DATA SOURCES

A systematic review was performed on definitive intraneural perineuriomas identified through Medline. Baylor College of Medicine-affiliated hospitals' anatomic pathology databases yielded 2 illustrative intraneural perineurioma cases.

STUDY SELECTION

Intraneural perineurioma inclusion criteria consisted of characteristic histology and confirmation of perineurial cell lineage by either immunohistochemistry (epithelial membrane antigen positive, S100 protein negative) and/or ultrastructural analysis (thin cytoplasmic processes with an incomplete basal lamina, poorly formed tight junctions, and pinocytotic vesicles).

DATA EXTRACTION

Clinicopathologic data were extracted from all identified articles, with subsequent statistical analysis of the following parameters: age, sex, race, tumor location, tumor size, duration of symptoms prior to diagnosis, treatment modalities and outcomes measures, follow-up assessment for tumor recurrence and metastasis, clinical features (history of trauma, motor/sensory abnormalities, clinical/family history), and diagnostic workup (routine histology, immunohistochemistry, ultrastructural analysis, and molecular/cytogenetic characteristics).

CONCLUSIONS

Intraneural perineurioma is a neoplastic proliferation of perineurial cells with unique immunohistochemistry and ultrastructural features, and it is distinct from other onion bulb Schwann cell-derived entities. Despite harboring molecular abnormalities of the long arm of chromosome 22, intraneural perineurioma has not been associated with neurofibromatosis. Intraneural perineurioma is a benign peripheral nerve sheath tumor that does not recur or metastasize.

INTRANEURAL PERINEURIOMA OF THE VIIITH CRANIAL NERVE

OBJECTIVE

The authors describe the clinical and pathological features of the second reported case of an intraneural perineurioma involving a major intracranial nerve and the first case of this entity involving the VIIIth cranial nerve.

CLINICAL PRESENTATION

A 59-year-old woman presented with a long history of dizziness, tinnitus, hearing loss, and unstable gait. A magnetic resonance imaging scan revealed a small intrameatal lesion, which showed no clear progression from 2000 to 2006.

INTERVENTION

As a result of worsening symptoms and a suspected vestibular schwannoma, an attempt of tumor resection through a retrosigmoid approach was performed. This revealed diffusely infiltrated and fusiform enlarged vestibular and cochlear nerves, with no identifiable border between the main tumor mass and normal nerve. An en bloc nerve-tumor mass excision was performed. The pathological findings confirmed the diagnosis of an intraneuronal perineurioma.

CONCLUSION

The experience with this unique case and the experience of others with the management of extracranial intraneural perineuriomas lead the authors to conclude that the most reasonable surgical management of this tumor at this location is a nerve-tumor cross-section resection.

Intraneural perineurioma of the third cranial nerve: occurrence and identification

✓Intraneural perineurioma is a true but rare neoplasm that originates from perineurial cells and mainly affects peripheral nerves. It must be distinguished from other hypertrophic neuropathies that are either inflammatory or demonstrate an onion-bulb formation that originates from Schwann cells. Complying with this strict definition, only three additional cases of cranium-related perineurioma have been identified: two lesions arose extracranially and involved cranial nerves, and one occurred intracranially but did not involve a nerve.

The authors describe a 27-year-old woman who presented with left third cranial nerve palsy and was found to harbor a mass lesion in the superior orbital fissure and cavernous sinus. After subtotal resection had been performed, pathological studies confirmed the presence of perineurial tumor cells in a pseudo–onion bulb formation. The cells stained positively for epithelial membrane antigen but not for S100 protein, clearly distinguishing the disease from one that originates in Schwann cells.