Tumeurs malignes des gaines nerveuses périphériques intracérébrales métastatiques : à propos de deux cas et revue exhaustive des cas de la littérature

Diagnosis and Treatment of Peripheral and Cranial Nerve Tumors with Expert Recommendations: An EUropean Network for RAre CANcers (EURACAN) Initiative

The 2021 WHO classification of the CNS Tumors identifies as "Peripheral nerve sheath tumors" (PNST) some entities with specific clinical and anatomical characteristics, histological and molecular markers, imaging findings, and aggressiveness. The Task Force has reviewed the evidence of diagnostic and therapeutic interventions, which is particularly low due to the rarity, and drawn recommendations accordingly. Tumor diagnosis is primarily based on hematoxylin and eosin-stained sections and immunohistochemistry. Molecular analysis is not essential to establish the histological nature of these tumors, although genetic analyses on DNA extracted from PNST (neurofibromas/schwannomas) is required to diagnose mosaic forms of NF1 and SPS. MRI is the gold-standard to delineate the extension with respect to adjacent structures. Gross-total resection is the first choice, and can be curative in benign lesions; however, the extent of resection must be balanced with preservation of nerve functioning. Radiotherapy can be omitted in benign tumors after complete resection and in NF-related tumors, due to the theoretic risk of secondary malignancies in a tumor-suppressor syndrome. Systemic therapy should be considered in incomplete resected plexiform neurofibromas/MPNSTs. MEK inhibitor selumetinib can be used in NF1 children ≥2 years with inoperable/symptomatic plexiform neurofibromas, while anthracycline-based treatment is the first choice for unresectable/locally advanced/metastatic MPNST. Clinical trials on other MEK1-2 inhibitors alone or in combination with mTOR inhibitors are under investigation in plexiform neurofibromas and MPNST, respectively.

Intracranial Malignant Peripheral Nerve Sheath Tumors Not Associated with a Cranial Nerve: Systematic Review and Illustrative Case

OBJECTIVE

Primary intracranial malignant peripheral nerve sheath tumors (MPNSTs) not associated with cranial nerves are rare and aggressive neoplasms. The rarity of presentation has precluded rigorous analysis of diagnosis, risk factors, treatment, and survival. We analyzed every reported case through exhaustive literature review. In addition, we present our own experience managed with resection, radiotherapy, and first use of targeted therapy in a tumor of this type for a BRAF mutation identified during next-generation sequencing.

METHODS

Two databases, PubMed and Embase, and crossed references were queried for intracranial MPNSTs not associated with a cranial nerve. Extracted variables included demographics, risk factors, tumor characteristics, interventions, and outcomes. Univariate and multivariate analysis was performed to identify factors with survival benefit.

RESULTS

A total of 56 patients (including the present case) were included from 743 literature results. There was a male/female ratio of 1.5:1 and mean diagnosis age of 29.7 ± 21.8 years. Seventy-one percent of cases were sporadic and 23% neurofibromatosis type 1 related. Median survival was 29 ± 22.1 months with 1-year survival of 60%. Factors associated on univariate analysis with reduced survival were subtotal resection (P = 0.05), older age (P = 0.023), triton histology (P < 0.001), and early recurrence (≤6 months) (P = 0.018). On multivariate analysis, gross total resection reduced mortality risk (P = 0.011), whereas triton histology (P = 0.017) and infratentorial tumor location (P = 0.037) increased mortality.

CONCLUSIONS

We present a systematic review of intracranial MPNSTs not associated with a cranial nerve. These tumors have poor prognosis and benefit from aggressive resection, multimodal treatment, and close follow-up. Next-generation sequencing can show molecular alterations for potential targeted therapy.

When "Peripheral" Becomes "Central": Primary and Secondary Malignant Intracerebral Nerve Sheath Tumor: A Case Report and a Systematic Review

BACKGROUND

The intracerebral occurrence of malignant peripheral nerve sheath tumors (MPNSTs) is exceedingly rare, and despite aggressive treatments, local recurrence and poor prognosis are very frequent. Like other brain tumors, these tumors could be primary or secondary, making the term "peripheral" an imprecise term for a primary brain tumor.

OBJECTIVE

To analyze the reported cases of primary and secondary cerebral MPSNTs in terms of diagnosis, treatment, and overall survival. Additionally, we present a case of malignant intracerebral nerve sheath tumor (MINST) treated with radical surgery and radiotherapy.

METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, one database (PubMed) and crossed references were queried for MPNST with brain metastasis and primary MINSTs from 1971 to 2020. Data regarding demographic features, primary tumor site, risk factors, brain location of the lesion, treatment applied, and overall survival were extracted.

RESULTS

A total of 55 patients were selected (including the reported case): 29 patients were secondary brain MPNST and 26 patients were primary MINST. The mean age was 41.8 ± 22 and 31.2 ± 23 yr, respectively. All brain metastases of MPNST (100%) had a primary tumor elsewhere in the body at the time of diagnosis. The overall survival was significantly shorter in patients with a secondary brain MPNST compared to MINST (P = .002).

CONCLUSION

We present a comprehensive analysis of every reported primary and secondary intracerebral MPNST. The prognosis in terms of survival is worst in the last one despite aggressive treatment. The lack of a primary MPNST in screening tests is sufficient to confirm a MINST at time of diagnosis.

Malignant intracerebral nerve sheath tumor in a patient with Noonan syndrome: illustrative case

BACKGROUND

Malignant peripheral nerve sheath tumors (MPNSTs) within the neuroaxis are rare, usually arising from peripheral and cranial nerves. Even more scarce are cranial subclassifications of MPNSTs termed “malignant intracerebral nerve sheath tumors” (MINSTs). These tumors are aggressive, with a strong tendency for metastasis. With this presentation, alongside resistance to adjunctive therapy, complete excision is the mainstay of treatment, although it is often insufficient, resulting in a high rate of mortality.

OBSERVATIONS

The authors report the case of an adult patient with a history of Noonan syndrome (NS) presenting with slowly progressive right-sided hemiparesis and right-sided focal motor seizures. Despite initial imaging and histology suggesting a left frontal lobe high-grade intrinsic tumor typical of a glioblastoma, subsequent molecular analysis confirmed a diagnosis of MINST. The patient’s neurological condition improved after gross-total resection and adjuvant chemo-radiation; he remains on follow-up.

LESSONS

MINSTs are rare neoplasms with a poor prognosis; management options are limited, with surgery being the cornerstone of treatment. Reports on rare tumors such as this will increase awareness of this particular pathology and disclose clinical experience. In this case, the authors were unable to establish a definite cause-and-effect relation between NS and MINST. Nevertheless, it remains the first reported case in the literature.

Malignant Intracerebral Nerve Sheath Tumor Presenting With Intratumoral Hemorrhage

BACKGROUND

Primary central nervous system sarcomas are rare primitive mesenchymal non-meningothelial tumors. Malignant peripheral nerve sheath tumor accounts for 5% of sarcomas, with an incidence of approximately 0.001% and a recognized association with neurofibromatosis type 1. Its intracranial subtype, the so-called malignant intracerebral nerve sheath tumor (MINST), is even more infrequent. Current knowledge about its clinical presentation and best therapeutic management is poor because of the limited number of cases reported in literature. Commonly, intratumoral hemorrhage occurs at the time of diagnosis and, notably, most patients had intracranial hemorrhage prior to definitive diagnosis.

CASE DESCRIPTION

We report a case of MINST in a young boy affected by neurofibromatosis type 1 who presented a spontaneous intracranial hemorrhage, successfully treated with surgery and postoperative adjuvant therapy. The tumor relapsed 1 year after and was successfully retreated with a second surgery.

CONCLUSIONS

Malignant intracerebral nerve sheath tumors are rare sarcomas that can be associated with intratumoral hemorrhage at the time of presentation, mostly in patients with neurofibromatosis type 1. Surgery promptly performed, associated with adjuvant therapy, can result in an encouraging survival rate.

Intracranial Malignant Nerve Sheath Tumor in the Middle Cranial Fossa: A Rare Case Report with Review of Literature

Intracranial malignant nerve sheath tumors rarely arise in the central nervous system. They usually arise from the cranial nerves, though rare cases of intraparenchymal lesions have also been reported. We report a case of malignant nerve sheath tumor located in the right middle cranial fossa. Preoperatively, the lesion resembled a meningioma arising from the petrous temporal bone. The lesion was completely excised. Postoperatively, the patient developed righted-sided complete facial nerve palsy. Histopathology and immunohistochemistry revealed the lesion to be a malignant nerve sheath tumor. The development of postoperative facial nerve palsy was puzzling but could be explained if we consider the possibility of the lesion arising from the facial nerve near the geniculate ganglion. Intracranial malignant nerve sheath tumor centered over the geniculate ganglion and projecting into the middle cranial fossa is uncommon, and to the best of our knowledge, only one such case has been previously reported. We review the relevant literature, discuss the management and add to the previously reported cases of this rare condition.