Early Genetic Diagnosis of Neurofibromatosis Type 2 From Skin Plaque Plexiform Schwannomas in Childhood

Systematic Characterization of the Clinical and Pathological Features of Schwannomas Harboring SH3PXD2A::HTRA1 Fusion

The understanding of schwannoma tumorigenesis has been reshaped by the recent identification of SH3PXD2A::HTRA1 fusion in 10% of intracranial/spinal schwannomas. Nonetheless, pathologic features of schwannomas harboring this fusion, as well as its prevalence outside intracranial/spinal locations, have not been characterized. We screened 215 consecutive schwannomas for their clinicopathologic characteristics and fusion status using reverse-transcriptase polymerase chain reaction (RT-PCR). Among 29 (13.5%) fusion-positive schwannomas, the most prevalent location was peripheral somatic tissue (30.7%, 19/62), followed by spinal/paraspinal (18.4%, 7/38), body cavity/deep structures (10%, 2/20), intracranial (1.3%, 1/75), and viscera (0/13). All 8 cellular, 4 microcystic/reticular, and 3 epithelioid schwannomas were fusion-negative, as were 41/42 nonschwannomatous peripheral nerve sheath tumors. Remarkably, a distinct 'serpentine' palisading pattern, comprising ovoid/plump cells shorter than usual schwannian cells in a hyalinized stroma, was identified in most fusion-positive cases and the schwannomatous component of the only fusion-positive malignant peripheral nerve sheath tumor. To validate this finding, 60 additional cases were collected, including 36 with (≥10% arbitrarily) and 24 without appreciable serpentine histology, of which 29 (80.6%) and 2 (8.3%) harbored the fusion, respectively. With percentages of 'serpentine' areas scored, 10% was determined as the optimal practical cut-off to predict the fusion status (sensitivity, 0.950; specificity, 0.943). Fusion positivity was significantly associated with serpentine histology, smaller tumors, younger patients, and peripheral somatic tissue, while multivariate logistic linear regression analysis only identified serpentine histology and location as independent fusion-predicting factors. RNA in situ hybridization successfully detected the fusion junction, highly concordant with RT-PCR results. Gene expression profiling on 18 schwannomas demonstrated segregation largely consistent with fusion status. Fusion-positive cases expressed significantly higher HTRA1 mRNA abundance, perhaps exploitable as a biomarker. In summary, we systematically characterize a series of 60 SH3PXD2A::HTRA1 fusion-positive schwannomas, showing their distinctive morphology and location-specific prevalence for the first time.

[Neurofibromatosis type 2 in the otorhinolaryngological practice]

Neurofibromatosis type 2 (NF2) is a rare autosomal dominant disease (frequency 1 in 25-90 000) characterized by the formation of tumors of the central nervous system due to a mutation in the NF2 gene on chromosome 22q12. Bilateral vestibular schwannomas are recognized as absolute diagnostic criteria of NF2 and occur in 95% of patients, are accompanied by hearing impairment, manifest at the age of 18-24 years. Skin manifestations can precede vestibular schwannomas for several years and predict the course of the disease: neurofibromas, cafe-au-lait macules, hypopigmented spots, recently described mesh capillary malformations. Despite the benign nature of schwannomas, they can lead to hearing loss, vestibular dysfunction, facial nerve paralysis, gait disorders, pain and convulsions, there is a risk of early death from compression of the brain stem. The probability of progressive hearing loss is partly determined by the type of mutation. We described a clinical case of NF2 in a 21-year-old patient with bilateral vestibular schwannomas without hearing loss, whose skin examination by ENT specialist revealed this disease. The importance of the presented observation is that the doctor should assume neurofibromatosis type 2 in a young patient with bilateral vestibular schwannomas. It is necessary to undertake a further examination of this patient, including: skin examination for the identification of characteristic neurofibromas and cafe-au-lait macules, consultation with an ophthalmologist, neurologist, MRI of the brain and spinal cord with contrast, genetic analysis - for timely initiation of therapy that prevents hearing loss and vestibular disorders.

Surgical Management of Peripheral Nerve Pathology in Patients With Neurofibromatosis Type 2

BACKGROUND

Neurofibromatosis type 2 (NF2) is rare genetic disorder mainly characterized by the development of central nervous system lesions, but peripheral nerve pathology may also cause high morbidity including pain, motor, and sensory loss.

OBJECTIVE

To describe the tumor burden of patients with peripheral nerve pathology in NF2 including peripheral neuropathies and schwannomas and the results of surgery in the latter group.

METHODS

We conducted a retrospective chart review of all patients with NF2 followed up at our NF2 Reference Center to include all patients suffering from peripheral nerve pathology. Tumor detection relied on focal MRIs based on symptoms.

RESULTS

Thirty-four patients harboring 105 peripheral nerve schwannomas and 1 perineurioma were included. Schwannomas were mainly located in major nerves (n = 74, 71%) compared with subcutaneous (n = 23, 22%) and intramuscular (n = 8, 7%) cases. Most schwannomas (81/90-90%) were classical discrete tumors while multinodular cases represented only 9 cases (10%). During follow-up, 63 (60%) tumors were operated in 24 patients, including 39 schwannomas of major nerves. A complete resection was achieved in most of the cases (52/63, 83%) with a complete relief of preoperative pain in most patients (57/60, 95%). Persistent motor deficits (5/39, 13%) were mostly encountered in patients operated from multinodular schwannomas (4/5, 80%). Six patients had an associated peripheral neuropathy with 5 cases of pseudo-Charcot-Marie-Tooth-associated amyotrophy.

CONCLUSION

Surgery remains a safe and effective method of treating peripheral nerve schwannoma-associated pain in NF2, with the exception of rare multinodular tumors. Special attention should be drawn to patients harboring severely debilitating neuropathies and perineuriomas.

Skin Lesions in Neurofibromatosis Type 2: Diagnostic and Prognostic Significance of Cutaneous (Plexiform) Schwannomas

Background

Neurofibromatosis type 2 (NF2) is a genetic disease characterized by the appearance of multiple tumours in the nervous system. Cutaneous lesions are common and may provide useful diagnostic and prognostic information, but they have not been widely studied.

Objectives

To characterize cutaneous lesions in a Spanish cohort of patients with NF2 and investigate associations with clinical and genetic severity.

Methods

We studied the clinical and histologic characteristics of cutaneous lesions in 49 patients with NF2 and analysed correlations with phenotype‐ and genotype‐based severity scores. We collected information on the presence/absence of cutaneous lesions, location, age at onset, type of lesion, and histologic features. We also studied level of systemic involvement and genetic mutations involved.

Results

Forty‐nine patients (31 women [63.3%] and 18 men [36.7%]) were analysed, and 33 (67.3%) had cutaneous lesions presumed to be schwannomas. According to their clinical form, they were distributed as follows: 24 patients (48%) had deep tumours, 21 (42%) had plaque‐like lesions, and 3 (6%) had superficial tumours. Histologic examination from 27 lesions analysed out 23 patients showed classic schwannoma or hybrid schwannoma‐neurofibroma features in the 8 deep tumours biopsied and plexiform schwannoma features in the 17 plaque‐like lesions and the 2 superficial tumours analysed. Early onset (first 2 decades of life) was reported by all patients with plaques and superficial tumours. In our cohort, 100% of the patients with plaque‐like lesions and superficial tumours with microscopic features of plexiform schwannoma were in the 2 groups with the most severe clinical phenotypes, and 82.6% of them were in the 3 most severe genotype‐based classes.

Conclusions and Relevance

Cutaneous lesions, specially plexiform schwannomas, are common in NF2, and they usually appear at an early age providing useful diagnostic and prognostic information. These tumours are part of the spectrum of cutaneous manifestations in this disease. Although its diagnostic and prognostic value has been pointed out, there are few studies focussed on their analysis.

Current Understanding of Neurofibromatosis Type 1, 2, and Schwannomatosis

Neurofibromatosis (NF) is a neurocutaneous syndrome characterized by the development of tumors of the central or peripheral nervous system including the brain, spinal cord, organs, skin, and bones. There are three types of NF: NF1 accounting for 96% of all cases, NF2 in 3%, and schwannomatosis (SWN) in <1%. The NF1 gene is located on chromosome 17q11.2, which encodes for a tumor suppressor protein, neurofibromin, that functions as a negative regulator of Ras/MAPK and PI3K/mTOR signaling pathways. The NF2 gene is identified on chromosome 22q12, which encodes for merlin, a tumor suppressor protein related to ezrin-radixin-moesin that modulates the activity of PI3K/AKT, Raf/MEK/ERK, and mTOR signaling pathways. In contrast, molecular insights on the different forms of SWN remain unclear. Inactivating mutations in the tumor suppressor genes SMARCB1 and LZTR1 are considered responsible for a majority of cases. Recently, treatment strategies to target specific genetic or molecular events involved in their tumorigenesis are developed. This study discusses molecular pathways and related targeted therapies for NF1, NF2, and SWN and reviews recent clinical trials which involve NF patients.

Review of Pediatric Head and Neck Neoplasms that Raise the Possibility of a Cancer Predisposition Syndrome

Cancer predisposition syndromes (CPS) are generally heritable conditions that predispose individuals to develop cancer at a higher rate and younger age than their representative general population. They are a significant cause of cancer related morbidity and mortality in the pediatric population. Therefore, recognition of lesions that may be associated with a CPS and alerting the clinicians to its implications is a crucial task for a diagnostic pathologist. In this review we discuss benign pediatric head and neck lesions associated with CPS namely: odontogenic keratocyst, juvenile nasopharyngeal angiofibroma, ossifying fibroma of the jaw, paraganglioma, plexiform neurofibroma, plexiform schwannoma, mucosal neuroma, and nevus sebaceous syndrome; along with malignant tumors such as squamous cell carcinoma. Several head and neck melanocytic, endocrine, and central nervous system tumors can also be associated with CPS; they are beyond the scope of this article. Nasal chondromesenchymal hamartoma is discussed elsewhere in this issue.

Visceral plexiform schwannoma: A case series

Plexiform schwannoma (PS) is a benign tumour of the peripheral nerve sheath that is typically found in the skin. Fewer than 15 cases of visceral PS have been reported to date in both adults and children. We herein discuss a series of 3 patients (2 male and 1 female) with abdominal PS, aged 10-16 years (mean age, 12 years). All the patients had an acute presentation with abdominal pain, which was associated with rectal bleeding in 1 case and with walking difficulties in 1 case. Radiological investigations included abdominal magnetic resonance imaging (MRI) and computed tomography, along with neurofibromatosis screening (cerebral MRI and dermatological evaluation). Complete removal of the mass was possible in 2 of the patients (in 1 case by laparoscopically assisted surgery). Follow-up was uneventful. Abdominal PS is a rare occurrence. Due to its possible association with neurofibromatosis, the diagnosis of PS should prompt an investigation for other manifestations of this disorder.

Primary Intrabulbar Neurofibroma

PURPOSE

Eye globe enucleation due to other than a malignant tumor is very rare today. Solitary intraocular neurofibroma without other signs of neurofibromatosis is a rare benign tumor and few cases have been reported to date.

MATERIAL AND METHODS

In 10 year interval from Jan 1 2007 to Dec 31 2016 we analyzed non-malignant eye globe enucleations.

RESULTS

Of the 49 enucleated blind eyes, each patient had visual acuity with no light perception, 34 (69.4%) were indicated for enucleation due to complications following previous postoperative surgery after trauma, 14 patients (28.6%) were due to secondary glaucoma and other complications following previous intraocular surgery, and in one patient (2%) the primary isolated intraocular neurofibroma was verified after enucleation.

CASE REPORT

A patient with isolated intrabulbar neurofibroma has been monitored since childhood for intraocular lesion and histologically verified at adult age. At the time of enucleation, he was 25 years old, squint since childhood and was observed for hamartoma in his right eye since he was 13 years old. Due to the progression of intrabulbar lesion, loss of visual acuity (functional state - no light perception) and secondary glaucoma, the right eye globe was enucleated at adult age and histopathological examination confirmed intraocular neurofibroma in the absence of neurofibromatosis.

CONCLUSION

Every enucleated eye globe should be subjected to a thorough histopathological examination. Isolated intraocular neurofibromas can occur as isolated orbital or intrabulbar masses without systemic features.

[Complex treatment of a patient with neurofibromatosis type 2]

Neurofibromatosis type 2, a rare disease, the most characteristic manifestation of which is the presence of bilateral vestibular schwannomas, less often schwannomas of other cranial, spinal and peripheral nerves. Much less frequent are meningiomas (intracranial, including meningiomas of the optic nerves, and spinal), epindymomas and gliomas. As a rule, in one patient several formations occur simultaneously, which creates a certain difficulty in treatment tactics. The authors present a case of type 2 neurofibromatosis in a 22-year-old female patient with multiple schwannomas of spinal roots and an atypical intraventricular meningioma.

The Diagnosis and Management of Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF1), NF2, and schwannomatosis are related, but distinct, tumor suppressor syndromes characterized by a predilection for tumors in the central and peripheral nervous systems. NF1 is one of the most common autosomal dominant conditions of the nervous system. NF1 has a high degree of variability in clinical presentation, which may include multiple neoplasms as well as cutaneous, vascular, bony, and cognitive features. Some of these manifestations overlap with other genetic conditions. Accurate diagnosis of NF1 is important for individualizing clinical care and genetic counseling. This article summarizes the clinical features, diagnostic work-up, and management of NF1.