Intraneural reticular perineurioma of the hypoglossal nerve

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.

Practical Approach to Histological Diagnosis of Peripheral Nerve Sheath Tumors: An Update

Peripheral nerve sheath tumors encompass a wide spectrum of lesions with different biological behavior, including both benign and malignant neoplasms as well as the recent diagnostic category, i.e., “atypical neurofibromatous neoplasm with uncertain biologic potential” to be used only for NF1 patients. Neurofibromas and schwannomas are benign Schwann-cell-derived peripheral nerve sheath tumors arising as isolated lesions or within the context of classical neurofibromatosis or schwannomatoses. Multiple tumors are a hallmark of neurofibromatosis type 1(NF1) and related forms, NF2-related-schwannomatosis (formerly NF2) or SMARCB1/LZTR1-related schwannomatoses. Perineuriomas are benign, mostly sporadic, peripheral nerve sheath tumors that show morphological, immunohistochemical, and ultrastructural features reminiscent of perineurial differentiation. Hybrid tumors exist, with the most common lesions represented by a variable mixture of neurofibromas, schwannomas, and perineuriomas. Conversely, malignant peripheral nerve sheath tumors are soft tissue sarcomas that may arise from a peripheral nerve or a pre-existing neurofibroma, and in about 50% of cases, these tumors are associated with NF1. The present review emphasizes the main clinicopathologic features of each pathological entity, focusing on the diagnostic clues and unusual morphological variants.

Clinical Features, Natural History, and Outcomes of Intraneural Perineuriomas: A Systematic Review of the Literature

BACKGROUND

Intraneural perineurioma is a rare peripheral nerve sheath tumor characterized by localized proliferation of perineurial cells. The literature consists predominantly of case reports and institutional series, with inconsistent and confusing nomenclature. We present a pooled analysis of all reported cases of intraneural perineurioma in the literature.

METHODS

A systematic search of PubMed, MEDLINE, Embase, and Scopus was performed according to PRISMA guidelines to identify all reported cases of intraneural perineurioma in the literature. Individual cases were pooled and analyzed for demographics, clinical features, and outcomes.

RESULTS

A total of 172 cases were identified across 72 studies, of which 149 were found in major peripheral nerves and their branches. Median age of patients at diagnosis and onset of symptoms was 18 years (interquartile range [IQR], 12-34 years) years and 13.5 years (IQR, 8-26 years), respectively, with 54.4% (81/149) being female. The most common sites were the sciatic nerve or its branches (41.9%), median nerve (13.5%), radial nerve (12.2%), and brachial plexus (12.2%). Most patients were managed conservatively (52.9%; 72/136). Among those managed conservatively with available follow-up (n = 31), median follow-up was 11 months, and most (67.7%, n = 21) reported no change in neurologic status, although worsening was noted in 29.0% (9/31). Among surgically managed cases (n = 64), the most common intervention was resection with or without repair (62.5%; 40/64), neurolysis (25%; 16/64), or tendon transfers without resection (12.5%; 8/64). No lesion recurred after surgical resection.

CONCLUSIONS

Intraneural perineurioma represents a benign focal lesion presenting with weakness and atrophy affecting adolescents and young adults. Most cases are managed nonoperatively and surgical treatment strategies are varied.

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.

[Reticular perineurioma of the tibial nerve]

Reticular (retiform) perineurioma is a rare variant of soft tissue perineurioma developed from the perineurium. This benign tumor is characterized by strands of spindle cells in a fibro-myxoid matrix surrounding pseudocystic mucoid spaces. We report a tibial nerve reticular perineurioma in a 35-year-old patient.

Ultrasound of the Hypoglossal Nerve in the Neck: Visualization and Initial Clinical Experience with Patients

BACKGROUND AND PURPOSE

The hypoglossal nerve, providing motor innervation for the tongue, can be affected in many diseases of the neck and skull base, leading to dysarthria, dysphagia, and ultimately atrophy of the tongue. We determined the feasibility of direct visualization of the hypoglossal nerve in the neck with ultrasound, testing this technique on healthy volunteers and evaluating it in clinical practice.

MATERIALS AND METHODS

The study consisted of 4 parts: first, ultrasound-guided perineural ink injections along the course of the hypoglossal nerve at 24 sides of 12 fresh, nonembalmed cadaver necks. Subsequently, the specimens were dissected to confirm the correct identification of the nerve. The second part was examination of healthy volunteers with ultrasound and measurement of cross-sectional areas for generating reference data. The third part was scanning of healthy volunteers by 2 resident physicians with little and intermediate experience in ultrasound. Fourth was examination with ultrasound of patients with motor symptoms of the tongue.

RESULTS

The hypoglossal nerve was correctly identified bilaterally in all cadaveric specimens (24/24) and all volunteers (33/33). The cross-sectional area ranged from 1.9 to 2.1 mm(2). The resident physicians were able to locate the nerve in 19 of 22 cases, demonstrating that locating the nerve is reproducible and feasible even with intermediate experience in ultrasound. Finally, alterations of the hypoglossal nerve in disease states could be depicted.

CONCLUSIONS

Direct, reliable, and reproducible visualization of the extracranial hypoglossal nerve with ultrasound is feasible.

Cutaneous microcystic/reticular schwannoma: a poorly recognized entity

BACKGROUND

Microcystic/ reticular schwannoma is exceptionally rare yet distinctive morphological variant of schwannoma with predilection for visceral sites lacking association with neurofibromatosis.

AIMS

To further delineate clinicopathological features of cutaneous microcystic/reticular schwannoma and to discuss its differential diagnosis.

RESULTS

We analyzed three cutaneous microcystic/reticular schwannomas, occurring in two males and one female (mean age: 37.6 years). The tumors presented as a non-painful slightly raised papule (mean: 0.7 cm) on upper arm (n = 2) and back (n = 1). No recurrences were observed despite marginal excision (mean follow up: 42 months). Histopathologically, a multilobular proliferation was present in the dermis composed of bland tumor cells forming distinctive microcystic, reticular, lace-like or pseudoglandular structures, containing abundant myxoid/mucinous material. By immunohistochemistry, tumor cells lining microcystic structures corresponded to Schwann cells (diffuse S100 positive, variable GFAP positivity). A discontinuous EMA-positive perineurium was present at the periphery of some of the lobules.

CONCLUSION

Cutaneous microcystic/reticular schwannoma expands the spectrum of benign peripheral nerve sheath tumors with reticular morphology encountered in the skin. Other tumors in this group include reticular perineurioma and hybrid tumors with reticular morphology, e.g. reticular perineurioma/schwannoma and reticular perineurioma/neurofibroma.

Rapid Recurrence of a Benign Meningial Perineurioma

BACKGROUND

We describe a rare case of a rapidly recurring benign meningial-based perineurioma. Clinical, radiologic, and pathologic features of a rapidly recurring falxial perineurioma are described; the perineurioma was discovered incidentally in an 86-year-old woman.

CASE DESCRIPTION

Due to progressive gait disturbances and radiologically proven progression after a 3-year symptom-free interval, subtotal resection of a large falxial-based meningeal tumor was performed.

CONCLUSIONS

The pathologic examination confirmed the diagnosis of a perineurioma (World Health Organization grade I). Follow-up magnetic resonance tomography 5 months later due to neurologic deterioration revealed an abnormally rapidly growing and extensive local tumor recurrence. Due to the mass effect, reoperation was performed and adjuvant radiation of 20 Gy to the tumor bed was implemented thereafter. Meningeal-based perineuriomas of the central nervous system are extremely rare, and literature on proper management is scarce. Although histologic classification reveals a benign lesion, follow-up may be considered for this type of tumor.

Malignant cell infiltration in the peripheral nervous system

The peripheral nervous system can be affected by malignancies involving different mechanisms. Neoplastic nerve lesion by compression, invasion, and infiltration is rare and occurs in particular in leukemia (neuroleukemiosis) and lymphoma (neurolymphomatosis). Its occurrence is much rarer in cancer, and even less so in sarcoma. The neoplastic infiltration of peripheral nerves by solid tumors is characterized by specific topographical sites such as the base of the skull, the ear, nose and throat region, and the cervico-brachial plexus as well as the lumbar and sacral plexus. Rarely malignant invasion affects the cranial nerves of the face where it can spread centripetally. Autonomic nerves and ganglia can also be affected. The retrograde spread of cancer in nerves is a bad prognostic sign. The clinical diagnosis is determined by tumor type, the pattern of involvement, and often pain.