Hybrid schwannoma/perineurioma of the spinal nerve: Multifocal occurrence, and recurrence as an intraneural perineurioma

Trigeminal hybrid nerve sheath tumor - a case report and literature review

BACKGROUND

Hybrid nerve sheath tumors (HNST) contain elements of more than one established sub-type of nerve sheath tumor and have been recently recognized in the 2016 WHO classification of central nervous system tumors. While common in the peripheral nerves and extracranial branches of cranial nerves, only one case has been previously documented of an intracranial HNST arising from a cranial nerve.

CASE DESCRIPTION

We describe a large, multi-compartmental intracranial hybrid nerve sheath tumor arising from the trigeminal nerve in a 22-year-old lady who presented with clinical and radiological features suggestive of a right cerebellopontine angle mass. Histopathological examination following retrosigmoid excision of the tumor revealed histological and immunohistochemical features of a schwannoma and a perineurioma.

CONCLUSIONS

HNSTs are likely to be underreported in the intracranial region. The clinical course of these tumors and the reason for their occurrence in this location are not known.

Hybrid tumors with perineurioma components: a systematic review of the literature and illustrative case

PURPOSE

Hybrid peripheral nerve sheath tumors (HPNST) are a newly recognized class of peripheral nerve sheath tumor, composed of at least two areas characteristic of perineurioma, schwannoma, or neurofibroma. The literature consists only of case reports and small series; therefore, we present an illustrative case and an analysis of all reported cases of HPNST with a perineurioma component in the literature.

METHODS

A systematic search of the literature was performed to identify all reported cases of hybrid perineurioma-schwannoma or perineurioma-neurofibroma in the world's literature. Individual cases were analyzed for demographics, clinical features, imaging, and outcomes.

RESULTS

A total of 159 cases were identified across 41 studies. Hybrid tumors tended to present in mid-adulthood (median 38.5 years), predominantly affected females (57%, 89/156), as a painless (63%, 63/100) mass, or swelling. Ten patients (10/74, 14%) had a history of neurofibromatosis 1, and 2 patients a history of neurofibromatosis 2 (2/74, 3%). The majority (78%, 122/157) of cases occurred superficially, most commonly in the lower extremity (25%, 39/157). Perineurioma-schwannoma was the most reported (86%, 137/159) pathologic diagnosis, with 3 cases presenting with malignant features. Two cases reocurred after resection.

CONCLUSION

HPNST tend to occur in mid-adulthood and present as slowly progressive, painless, superficial masses, with a heterogeneous appearance on imaging. These entities pose a unique diagnostic challenge and likely remain under-recognized in the literature and current clinical practice. They pose low risk of recurrence or malignant transformation, and future work regarding the association with neurofibromatosis and genetic profiles is needed.

A Rare Perineurioma/Granular Cell Tumor Hybrid Peripheral Nerve Sheath Tumor

Hybrid peripheral nerve sheath tumors (PNSTs) are rare benign composite neoplasms demonstrating features of multiple endogenous nerve sheath cell types. Hybrid PNSTs with granular cell components are exceedingly rare. Only a handful number of hybrid PNSTs composed of granular cell tumor and perineurioma have been described to date. We present a rare hybrid of perineurioma and granular cell tumor and review the literature.

Hybrid Schwannoma/Perineurioma: Morphologic Variations and Genetic Profiles

To clarify the morphologic spectrum and molecular profiles of hybrid schwannoma/perineurioma (HSP), we investigated 15 tumors clinicopathologically and cytogenetically. HSP was classified into 2 morphologic types: mixed cellular and combined tumor types. The former comprising of 14 tumors mostly arose in the subcutaneous tissue of the extremities and the trunk of middle-aged adults. They were well-circumscribed and composed of elongated spindle-shaped tumor cells arranged in storiform and whorl patterns. Immunostaining revealed a mixed cellular proliferation of S-100 protein-positive and SOX10-positive Schwann cells and epithelial membrane antigen-positive, claudin 1-positive, and GLUT1-positive perineurial cells. During follow-up, no tumors were found to have recurred in any cases. In contrast, in the combined tumor type arising in the mediastinum of a young male with neurofibromatosis type 2, the intraneural perineurioma-like areas, characterized by small whorl-like structures, were present in plexiform schwannoma-like areas. No recurrence was noted in the case. Molecular analyses (array comparative genomic hybridization and fluorescence in situ hybridization) revealed LOH 22q in 2 tumors of 5 studied: one each of the mixed cellular and combined tumor types. Although the same diagnostic term, HSP, has been applied to both mixed and combined types, they should be separated from each other.

Primary intraosseous hybrid epithelioid schwannoma/perineurioma in the proximal tibia: a case report of benign hybrid neoplasm with local hypercellularity

Background

As a new entity included in the 4th edition of the WHO classification of tumours of soft tissue and bone in 2013, hybrid peripheral nerve sheath tumours are benign composite neoplasms that demonstrate features of more than one type of nerve sheath tumour, with a wide age distribution and a predilection for superficial location. Those involving deep sites are relatively rare. To the best of our knowledge, only one case of primary intraosseous hybrid peripheral nerve sheath tumours has been documented. In this article, we report another case of hybrid peripheral nerve sheath tumours occurring in bone with different clinical, radiological and pathological features from those in the previously reported cases.

Case presentation

A 28-year-old female presented with a painful nodule in the right tibia. Radiological examination revealed an oval eccentric osteolytic lesion in the proximal tibia. Histologically, the circumscribed but unencapsulated lesion demonstrated biphasic cellular differentiation. Bland, small epithelioid cells arranged in clusters in the myxoid or collagenous stroma and inconspicuous spindle cells scattered in the hypercellular areas were suggested to originate from Schwann cells according to the detection of S100. Both the elongated spindle cells with thin, wavy nuclei and the spindle cells in fascicular or storiform pattern in hypercellular areas showed a positive immunoreaction for epithelial membrane antigen, indicating perineurial differentiation. Based on histological and immunochemical examinations, the patient was diagnosed with hybrid epithelioid schwannoma/perineurioma. The lesion was resected and has not recurred for 8 months since resection.

Conclusion

The present case is the second primary intraosseous hybrid peripheral nerve sheath tumour to be reported. This is also the first reported intraosseous tumour composed of epithelioid schwannoma and perineurioma with hypercellularity, indicating diverse involvement sites and a wide range of histological features among hybrid peripheral nerve sheath tumours. Awareness of such diversity is critical for accurate diagnoses. The morphological overlap with other spindle and epithelioid cell neoplasms, especially pure peripheral nerve sheath tumours, requires that immunochemical and molecular examinations be used as objective tools to provide the necessary information for a differential diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s13000-019-0829-x) contains supplementary material, which is available to authorized users.

Benign Cutaneous Peripheral Nerve Sheath Tumor with Hybrid Features: Report of Two Cases with Schwannoma/Perineurioma and Schwannoma/Neurofibroma Components

Hybrid benign peripheral nerve sheath tumors are rare tumors exhibiting areas of more than one neural neoplasm such as schwannoma/neurofibroma, neurofibroma/perineurioma, or schwannoma/perineurioma. These tumors usually arise in the skin of the extremities and trunk, and less commonly affect extracutaneous sites. Here we report two cases of these tumors exhibiting hybrid features of schwannoma/perineurioma and schwannoma/neurofibroma located in the scalp and the ankle, respectively.

Hybrid peripheral nerve sheath tumors: report of five cases and detailed review of literature

BACKGROUND

Hybrid peripheral nerve sheath tumors (PNSTs) have been recognized recently and were first included in the 4th edition of World Health Organization (WHO) Classification of Tumors of Soft tissue and Bone, published in 2013. These tumors show combined features of more than one type of conventional benign peripheral nerve sheath tumors. The most common combinations are those of schwannoma/perineurioma followed by combinations of neurofibroma/schwannoma and neurofibroma/perineurioma. A detailed literature review of published cases is presented. We have discussed the types and etiology, epidemiology and sites of localization, gross and microscopic appearances and immunohistochemical features of hybrid PNSTs and association of these tumors with tumor syndromes.

CASE PRESENTATION

We have included five cases which were diagnosed in our department as we believe that publication of these new cases is relevant for the improved understanding of these specific tumors. Four of our five patients were males, mean age was 24 years. There was wide variation in the location of these tumors. Mean size of excised tumors was 5.5 cms in the greatest dimensions. Three out of five cases represented hybrid schwannoma/perineurioma histologically. No significant nuclear atypia, mitotic activity or necrosis seen. All five cases were completely excised. All five patients are alive and well at the time of writing with no recurrence.

CONCLUSION

Hybrid PNSTs are distinct tumors and are usually benign. However, rare case reports have described local recurrence and at least two recent case reports have described malignant transformation in these tumors. Further studies on large number of cases are required to determine the exact pathogenetic basis of these tumors.

Can Intraneural Perineuriomas Occur Intradurally? An Anatomic Perspective

BACKGROUND: Intraneural perineuriomas are rare, benign lesions produced by the neoplastic proliferation of perineurial cells. They typically present in adolescents and affect nerves of the limbs. In our experience, we have not encountered a single case of classic intraneural perineurioma at an intradural location.

OBJECTIVE: To determine whether intraneural perineuriomas could occur intradurally, given the prevalence of intradural nerve sheath tumors, and explain our findings with an anatomic perspective.

METHODS: We retrospectively reviewed the high-resolution magnetic resonance images of 56 patients from an institutional registry of patients with intraneural perineurioma. All cases were analyzed for signs of proximal extension toward spinal nerves, roots, and spinal cord. A literature review was performed. The clinical, radiological, and histopathological features of potential intradural lesions were critically appraised against strict criteria for a diagnosis of classic intraneural perineurioma.

RESULTS: Fifteen of 56 (27%) patients with intraneural perineurioma had a proximal localization in the lumbosacral or brachial plexus. Not a single case occurred proximal to the dorsal root ganglia (DRG). One case of trigeminal intraneural perineurioma occurred distal to the gasserian ganglion. A literature review did not reveal any convincing cases of classic intraneural perineuriomas occurring in an intraspinal intradural location and revealed only 1 possible case in an intracranial intradural location.

CONCLUSION: Based on our study, the occurrence of classic intraneural perineuriomas intradurally is exceedingly rare, if at all present. This may be related to the paucity of perineurial cells at the nerve root level and reciprocal interactions between neuroglial cells at the central-to-peripheral transition zones.