Hybrid Neurofibroma/Schwannoma of the Orbit

Hybrid peripheral nerve sheath tumours: MRI features with pathological correlation in 24 cases

OBJECTIVES

To describe the MRI features of histologically proven hybrid peripheral nerve sheath tumours (HPNST).

METHODS

A retrospective analysis of the MRI features of 24 histologically proven cases of HPNST over 7 years. Demographic data obtained from clinical records included age, gender, and date of diagnosis. Two readers independently assessed MRI studies and assessed the following features: involvement of a major nerve, intramuscular location, lesion morphology, entering nerve sign, exiting nerve sign, target sign, fascicular sign, split fat sign, and ancient change (cystic change). Inter-observer agreement was assessed with Cohen's kappa coefficient. Histological diagnosis was based on either image-guided needle biopsy or resection histology.

RESULTS

The study included 9 males and 15 females with mean age 50 years (range: 24-78 years). Nine tumours (35%) involved a major nerve including spinal roots (5), radial (1), median (1), tibial (1), and axillary (1), while 5 (21%) tumours were intramuscular. The mean tumour size was 4.2 cm (standard deviation of 2.4 cm). The frequency of MRI features was as follows: lobular contour (71%; 17/24), ancient change (38%; 9/24), fascicular sign (17%; 4/24), entering nerve sign (21%; 5/24), exiting nerve sign (13%; 3/24), target sign (13%; 3/24), and split fat sign (8%; 2/24). Inter-observer agreement was high, ranging from 0.7 to 0.83.

CONCLUSIONS

HPNST infrequently demonstrate the classical MRI signs of benign peripheral nerve sheath tumours, but commonly have a lobular morphology and can show ancient/cystic change.

ADVANCES IN KNOWLEDGE

This is the first study in the literature analysing the MRI features of histologically proven HPNST. HPNST infrequently shows the classical MRI signs that would be expected with benign peripheral nerve sheath tumours although commonly have a lobular morphology and show cystic change.

Hybrid Neurofibroma/Schwannoma of the Oral Cavity: A Rare Case Report and Literature Review

Hybrid peripheral nerve sheath tumors show combined features of more than one type of conventional benign peripheral nerve sheath tumors. There are few cases reported of hybrid peripheral nerve sheath tumors in the head and neck region. A 68-year-old female patient was referred for evaluation of an oral swelling lasting five years. Intraoral examination revealed a small mobile nodule located in the lower vestibule. The patient underwent excisional biopsy and microscopic evaluation showed typical features of neurofibroma enclosing areas with palisading nuclei compatible with Antoni A pattern, which are seen in schwannomas. These regions showed strong and diffuse immunoreactivity for S100 protein and moderate positivity in the neurofibroma area. CD34 was positive in the neurofibroma area and entrapped axons were positive for neurofilament. The final diagnosis was oral hybrid neurofibroma-schwannoma tumor. Hybrid peripheral nerve sheath tumors, although extremely rare, may arise within the oral cavity. To the best of our knowledge, this is the first neurofibroma-schwannoma tumor reported in the oral cavity. Recognizing hybrid peripheral nerve sheath tumors as a distinct clinicopathological entity is important because they may also be associated with syndromic disorders.

Hybrid neurofibroma/schwannoma of the orbit

Hybrid neurofibroma/schwannoma is a rare variant of hybrid peripheral nerve sheath tumours (HPNST). A Medline search up to December 2021 identified only six cases of this tumour in the orbit. We report the case of a 78-year-old man who presented with left exophthalmos. Computed tomography showed a left intraconal orbital mass. The clinico-radiological diagnosis was consistent with an intraconal cavernous angioma. Orbitotomy was performed, obtaining an 18×16×11mm mass. Two different morphologies were seen microscopically, diagnostic of hybrid neurofibroma/schwannoma. HPNSTs of the orbit are uncommon and most reported cases showed a hybrid neurofibroma/schwannoma morphology. Hybrid neurofibroma/schwannomas have been associated with neurofibromatosis and schwannomatosis. Local recurrences have been reported. The correct identification of these tumours is important due to their potential use as a syndromic marker.

Intraconal Retro-Orbital B-Type Antoni Neurinoma Causing Vision Loss

Schwannoma is a rare benign tumor, originating from Schwann cells of the peripheral nerve sheath. We describe a case of intraconal orbital schwannoma, causing compression to the optic nerve and progressive visual impairment treated with surgical resection. The diagnosis of benign orbital schwannoma was provided by histopathological examination (large spindle cell tumor with AntoniB-type cell pattern) and also with immunohistochemistry (positivity for S-100 protein). The 6 months' follow-up was performed. The patient was asymptomatic during the 6-month follow-up.

Orbital exenteration: A 20-year experience from a tertiary center in Taiwan

PURPOSE

To describe the prognostic factors and survival outcomes in patients who underwent orbital exenteration surgery at a tertiary center over a 20-year period.

METHODS

This institutional retrospective study reviewed all patients who underwent orbital exenteration between January 1999 and January 2019 at Department of Ophthalmology, National Taiwan University Hospital. Patient demographics, tumor site, histopathology, status of surgical margins, additional resection, local recurrence, metastases, survival, and treatment data were recorded. Log-rank tests were used to verify the difference in survival curves among various potential prognostic factors.

RESULTS

Thirty patients (27 with malignancy, 1 with hybrid neurofibroma/schwannoma, and 2 with mucormycosis) were included. Malignant melanoma (n = 11) and sebaceous gland carcinoma (n = 8) were the most common indications for exenteration. Survival rates were 83% at 1 year, 42% at 3 years, and 33% at 5 years. Among patients with malignancies, 71% patients had clear margins after exenteration. All the incidences of local recurrence developed in the first 2 years postoperatively. Postoperative survival was significantly related to lymphovascular invasion (p = 0.018), but was independent from surgical margins, presence of metastasis, local recurrence, or perineural invasion.

CONCLUSION

We found worse prognosis with positive lymphovascular invasion. Although not significant, malignant melanoma showed poorer survival times compared to sebaceous gland carcinoma. Close follow-up, especially in the first 2 years after orbital exenteration, is crucial to identify disease recurrence.

Orbital hybrid peripheral nerve sheath tumors

Hybrid peripheral nerve sheath tumors (HPNST) are recently classified tumors from the World Health Organization Classification of soft tissue tumors that display combined features of more than one peripheral nerve sheath tumor. Acknowledgment is important because of its association with the development of neurofibromatosis type 1, type 2, and schwannomatosis. Orbital involvement is rare and only six cases of HPNST have been documented on literature. This article serves to review the pathophysiology, clinical manifestation, diagnosis, treatment, and prognosis of this infrequent but important orbital tumor.

Hybrid nerve sheath tumor in the orbit: A case report and review of literature

Background:

In neurosurgical practice, we rarely encounter hybrid nerve sheath tumors (HNST) in the orbit. We recently had a patient of this rare tumor. We believe that this is the first report where we resected the tumor transcranially.

Case Description:

A 54-year-old male presented with the left proptosis and intraconal tumor of 43 mm. We performed fronto-orbital craniotomy to resect the tumor mass. His proptosis completely improved and discharged home with a modified Rankin Scale of 1.

Conclusion:

Transcranial resection of orbital HNST was a safe and effective way to treat. Since we do not have much data regarding this rare tumor, we need to accumulate more cases.