ERN GENTURIS clinical practice guidelines for the diagnosis, treatment, management and surveillance of people with schwannomatosis

Familial schwannomatosis carrying LZTR1 variant p.R340X with brain tumor: A case report

Schwannomatosis (SWN) is a rare genetic condition characterized by the risk of developing multiple benign peripheral nerve sheath tumors; however, the risk of developing malignant tumors in patients with SWN remains unclear. This study described the case of a 57-year-old Japanese man diagnosed with SWN whose older brother also had SWN. Whole-exome sequencing identified a heterozygous mutation [c.1018C > T (p.Arg340X)] in the LZTR1 gene, linked to the RAS/MAPK pathway, in the patient and his brother. Moreover, the patient had aphasia and right-sided paralysis because of a brain tumor. RNA sequencing revealed the remarkable upregulation of several genes associated with oxidative stress, such as the reactive oxygen species pathway and oxidative phosphorylation, a downstream effector of the RAS/MAPK pathway, in the the patient and his brother compared with healthy volunteers. The final diagnosis was LZTR1-related familial SWN, and the dysregulated RAS/MAPK pathway in this patient might be associated with brain tumorigenesis.

Case of submandibular schwannoma and review of literature

Schwannomas are slow growing, benign tumours arising from Schwann cells. They are usually solitary and are sometimes associated with Neurofibromatosis type 1 and 2. As reported by Okada et al., while approximately 25%-40% of extra-cranial schwannomas occur in the head and neck region, Schwannomas of the oral cavity are very uncommon, accounting for only 1% of all Schwannomas. We report a case of a sublingual schwannoma in a 47-year-old female, discovered incidentally during the workup for tinnitus. The radiological and histopathological findings, along with a literature review, are presented.

Nerve enlargement in patients with Noonan syndrome: A retrospective cohort study

Noonan syndrome (NS) is an autosomal dominant condition characterized by facial dysmorphism, congenital heart disease, development delay, growth retardation and lymphatic disease. It is caused by germline pathogenic variants in genes encoding proteins in the Ras/mitogen-activated protein kinase signaling pathway. Nerve enlargement is not generally considered as a feature of NS, although some cases have been reported. High-resolution nerve ultrasound enables detailed anatomical assessment of peripheral nerves and can show enlarged nerves. This retrospective cohort study aims to describe the sonographic findings of patients with NS performed during a 1-year time period. Data on the degree of enlargement, the relation to increasing age, pain in extremities, genotype on the gene level and clinical features were collected. Twenty-nine of 93 patients visiting the NS Center of Expertise of the Radboud University Medical Center Nijmegen underwent high-resolution ultrasound. In 24 patients (83%) nerve enlargement was found. Most of them experienced pain. We observed a weak correlation with increasing age and the degree of nerve enlargement but no association with pain, genotype at the gene level or clinical features. This study shows that patients with NS have a high predisposition for sonographic nerve enlargement and that the majority experience pain.

NF2-related schwannomatosis and other schwannomatosis: an updated genetic and epidemiological study

OBJECTIVES

New diagnostic criteria for NF2-related schwannomatosis (NF2) were published in 2022. An updated UK prevalence was generated in accordance with these, with an emphasis on the rate of de novo NF2 (a 50% frequency is widely quoted in genetic counselling). The distribution of variant types among de novo and familial NF2 cases was also assessed.

METHODS

The UK National NF2 database identifies patients meeting updated NF2 criteria from a highly ascertained population cared for by England's specialised service. Diagnostic prevalence was assessed on 1 February 2023. Molecular analysis of blood and, where possible, tumour specimens for NF2, LZTR1 and SMARCB1 was performed.

RESULTS

1084 living NF2 patients were identified on prevalence day (equivalent to 1 in 61 332). The proportion with NF2 inherited from an affected parent was only 23% in England. If people without a confirmed molecular diagnosis or bilateral vestibular schwannoma are excluded, the frequency of de novo NF2 remains high (72%). Of the identified de novo cases, almost half were mosaic. The most common variant type was nonsense variants, accounting for 173/697 (24.8%) of people with an established variant, but only 18/235 (7.7%) with an inherited NF2 pathogenic variant (p<0.0001). Missense variants had the highest proportion of familial association (56%). The prevalence of LZTR1-related schwannomatosis and SMARCB1-related schwannomatosis was 1 in 527 000 and 1 in 1.1M, respectively, 8.4-18.4 times lower than NF2.

CONCLUSIONS

This work confirms a much higher rate of de novo NF2 than previously reported and highlights the benefits of maintaining patient databases for accurate counselling.

[Features of course of pain syndrome in patients with schwannomatosis]

OBJECTIVE

To identify the characteristics of pain syndrome in patients with schwannomas depending on genetic predisposition.

MATERIAL AND METHODS

The study included 46 patients with peripheral, spinal and intracranial schwannomas, corresponding to the schwannomatosis phenotype according to the 2022 clinical criteria. All patients underwent sequencing of the LZRT1, Nf2 and SMARCB1 and a copy number study in the NF2.

RESULTS

The most severe widespread pain was observed in patients with pathogenic LZRT1 variants, while patients with mosaic variants may not even have local tumor-related pain. Patients with SMARCB1variants may have no pain or have localized pain that responds well to surgical treatment.

CONCLUSION

Further studies of the molecular features of schwannomatosis and driver mutations in the pathogenesis of pain are necessary to improve the effectiveness of pain therapy in this group of patients. Schwannomatosis is a disease from the group of neurofibromatosis, manifested by the development of multiple schwannomas. Neuropathic pain is one of the main symptoms characteristic of peripheral schwannomas, however, the severity and prevalence of the pain syndrome does not always correlate with the location of the tumors. According to modern concepts, the key factors influencing the characteristics of the pain syndrome are the target gene and the type of pathogenic variant. The most severe widespread pain is observed in patients with pathogenic variants in the LZRT1 gene, while patients with mosaic variants may not even have local pain associated with tumors. Patients with variants in SMARCB1 may have no pain or localized pain that responds well to surgical treatment.

Management of Central and Peripheral Nervous System Tumors in Patients with Neurofibromatosis

Neurofibromatosis type I (NF1), neurofibromatosis type 2 (NF2), and schwannomatosis represent a diverse group of genetic tumor predisposition syndromes with a shared feature of tumors affecting the peripheral nerve sheaths. PURPOSE OF REVIEW: Many advancements have been made in understanding the biologic underpinnings of these conditions, and in 2016 the first drug was approved by the FDA to treat pediatric symptomatic unresectable plexiform neurofibromas. RECENT FINDINGS: Mek inhibitors have provided a much-needed therapeutic avenue for NF1 patients with unresectable plexiform neurofibromas (PN), both for reduction of tumor bulk and for improvement in symptoms. Selumetinib is the first FDA approved drug for PN, but is only approved for children. Some research suggests that alternative Mek inhibitors and other mixed tyrosine kinase inhibitors may have better efficacy in adults. Vascular endothelial growth factor (VEGF) inhibitor bevacizumab can prolong hearing and delay the need for surgery in NF2 patients with bilateral vestibular schwannomas. This article provides an update regarding considerations and approaches when treating the tumors associated with the neurofibromatoses (NF), including risk and prognosis metrics, clinical trial results, surgical techniques, and radiation therapy recommendations.

Schwannomatosis: a Realm Reborn: year one

PURPOSE OF REVIEW

In 2022, an international consensus recommendation revised the nomenclature for neurofibromatosis type 2 ( NF2 ) and Schwannomatosis (SWN), now grouped under the umbrella term Schwannomatosis, and defined new diagnostic criteria.

RECENT FINDINGS

This review describes the molecular criteria for diagnosis of schwannomatosis and the subsequent diagnosis strategy, while setting out the most recent advances in our understanding of the natural history, pathology, molecular biology and treatment of schwannomatosis-associated tumors, including schwannomas, meningiomas and ependymomas.

SUMMARY

Somatic mutation screening should become a new standard for the diagnosis of NF2 -, LTZTR1 -, SMARCB1 - and 22q-schwannomatosis to discriminate those conditions. Constitutional events in NF2 -Schwannomatosis have a major influence on disease severity and justifiably motivate ongoing efforts on gene replacement therapy research. On the other hand, underlying mechanisms of disease severity and associated pain remain largely unknown in non- NF2 -SWN and independent of germline mutation. Research efforts therefore focus on pain relief in ongoing trials and the discovery of new molecular mechanisms underlying schwannoma tumorigenesis/pain/neuropathies.

Surgical management of sporadic and schwannomatosis-associated pelvic schwannomas

Pelvic schwannomas are rare tumors that may occur either sporadically or in the context of schwannomatosis. We retrospectively reviewed the charts of patients harboring a pelvic schwannoma under conservative management or operated at our reference center between 2016 and 2023. All patients were operated by a multidisciplinary team, combining a vascular surgeon and a neurosurgeon. Twenty-four patients harboring 33 pelvic tumors were included in the cohort, including 12 patients with sporadic lesions, 2 patients with NF2-related schwannomatosis, and 10 patients with NF2-independent schwannomatosis. Multi-nodular tumors were more frequent in schwannomatosis compared to sporadic cases (p = 0.005). The mean age at diagnosis was 41 years old. Schwannomas were located on branches of the sciatic nerve (23/33, 70%), the femoral nerve (6/33, 18%), and the obturator nerve (4/33, 12%). Over the course of the study, 16 patients were operated, including 11 sporadic cases. The indication for surgery was pain (12/16, 75%) or tumor growth (4/16, 25%). Complete resection was achieved in 14 of 16 patients (87%). The mean post-operative follow-up was 37 months (range: 2-168 months). At last-follow-up, complete pain relief was achieved in all 12 patients with pre-operative pain. Post-operative morbidity included 3 long-term localized numbness and one MRC class 4 motor deficit in a multi-nodular tumor in a schwannomatosis patient. Despite its limited size, our series suggests that nerve-sparing resection of pelvic schwannomas offers satisfying rates of functional outcome both in sporadic and schwannomatosis cases, except for multi-nodular tumors.

Neurofibromatosis- and schwannomatosis-associated tumors: Approaches to genetic testing and counseling considerations

Neurofibromatosis (NF) and schwannomatosis (SWN) are genetic conditions characterized by the risk of developing nervous system tumors. Recently revised diagnostic criteria include the addition of genetic testing to confirm a pathogenic variant, as well as to detect the presence of mosaicism. Therefore, the use and interpretation of both germline and tumor-based testing have increasing importance in the diagnostic approach, treatment decisions, and risk stratification of these conditions. This focused review discusses approaches to genetic testing of NF- and SWN-related tumor types, which are somewhat rare and perhaps lesser known to non-specialized clinicians. These include gastrointestinal stromal tumors, breast cancer, plexiform neurofibromas with or without transformation to malignant peripheral nerve sheath tumors, gliomas, and schwannomas, and emphasizes the need for inclusion of genetic providers in patient care and appropriate pre- and post-test education, genetic counseling, and focused evaluation by a medical geneticist or other healthcare provider familiar with clinical manifestations of these disorders.

Clinical characteristics and prognosis of cystic degeneration in retroperitoneal schwannoma: A retrospective study of 79 patients

BACKGROUND AND PURPOSE

Diagnosis of retroperitoneal schwannoma (RS), especially cystic RS, is frequently missed or delayed owing to its rarity, location, nonspecific symptoms, and similarities with other tumors on various imaging modalities. This study aimed to determine associations between clinical, radiological, and histopathologic features and outcome.

MATERIALS AND METHODS

Seventy-nine patients with pathologically confirmed RS who underwent tumor resection between June 2010 and June 2020 were retrospectively reviewed and analyzed. Patients were stratified into three groups according to degree of tumoral cystic degeneration.

RESULTS

Cystic degeneration was significantly associated with multiple foci (p = 0.025), calcification (p = 0.012), and hemorrhage (p = 0.000), but not size (p = 0.08), high Ki-67 (p = 0.094), malignancy (p = 0.115; prevalence of cystic degeneration in the benign and malignant groups were 53.9% vs 100%), rough margin (p = 0.162), or irregular shape (p = 0.369). Malignant RS was significantly associated with multiple lymph nodes enlargement (p = 0.034). Tumor size, margins, shape, or/and multiplicity did not significantly differ between benign and malignant tumors. No recurrence occurred in patients with benign RS (mean follow-up, 45 months). All malignant tumors recurred; mean time to recurrence was 11.4 months (mean follow-up, 33 months).

CONCLUSION

Since RS is misdiagnosed mostly as malignancy and diagnosis is often delayed, a suspicion is necessary for diagnosis when atypical features are present. In RS, cystic degeneration was not associated with tumor size, Ki-67, or malignancy; however, it was significantly associated with multiple foci, calcification, and hemorrhage. Cystic degeneration and related factors are useful for the diagnosis of RS. Malignant RS should be considered when a mass involves multiple lymph nodes. Margins, morphology, and size are not associated with malignancy. Pathological tumor type, tumor location, and adjacent anatomic structures are associated with outcome.

Oculomotor nerve palsy in neurofibromatosis type 2

Neurofibromatosis (NF) type 2 is a rare neurological, autosomal dominant and genetic disorder. It is caused by a mutation in the tumor suppressor gene, called NF2 gene. The disorder results in several benign tumors of the nervous system. These typically include vestibular schwannomas, meningiomas, and ependymomas. Multiple cranial nerve abnormalities affect the brain, spinal cord, nerves, and skin and cause significant morbidity in patients. We describe a 20-year-old patient, with a family history of brain tumors, with symptoms of left sided third nerve palsy. Magnetic Resonance Imaging (MRI) of the brain and orbits revealed a small sized cavernous sinus meningioma and bilateral vestibular schwannomas. As per the differential diagnosis and optimal resolution brain imaging, NF2 was diagnosed. The patient was referred for specific treatment to the neuro-oncology unit. The case is distinct as the patient presented with a parasellar meningioma leading to third nerve palsy besides bilateral vestibular schwannomas. Manchester criteria and high contrast MR imaging proved more beneficial in our patient for the diagnosis of a wider clinical spectrum of NF2.

Understanding barriers to diagnosis in a rare, genetic disease: Delays and errors in diagnosing schwannomatosis

Diagnosis of rare, genetic diseases is challenging, but conceptual frameworks of the diagnostic process can guide quality improvement initiatives. Using the National Academy of Medicine diagnostic framework, we assessed the extent of, and reasons for diagnostic delays and diagnostic errors in schwannomatosis, a neurogenetic syndrome characterized by nerve sheath tumors and chronic pain. We reviewed the medical records of 97 people with confirmed or probable schwannomatosis seen in two US tertiary care clinics. Time-to-event analysis revealed a median time from first symptom to diagnosis of 16.7 years (95% CI, 7.5-26.0 years) and median time from first medical consultation to diagnosis of 9.8 years (95% CI, 3.5-16.2 years). Factors associated with longer times to diagnosis included initial signs/symptoms that were intermittent, non-specific, or occurred at younger ages (p < 0.05). Thirty-six percent of patients were misdiagnosed; misdiagnoses were of underlying genetic condition (18.6%), pain etiology (16.5%), and nerve sheath tumor presence/pathology (11.3%) (non-mutually exclusive categories). One-fifth (19.6%) of patients had a clear missed opportunity for genetics workup that could have led to an earlier schwannomatosis diagnosis. These results suggest that interventions in clinician education, genetic testing availability, expert review of pathology findings, and automatic triggers for genetics referrals may improve diagnosis of schwannomatosis.