Nerve Sheath Tumors Research Articles

Epidemiologic and survival analysis of malignant peripheral nerve sheath tumors: a retrospective cohort study.

Epidemiologic and survival analysis of malignant peripheral nerve sheath tumors: a retrospective cohort study.

Myelomodulatory treatments augment the therapeutic benefit of oncolytic viroimmunotherapy in murine models of malignant peripheral nerve sheath tumors.

Malignant peripheral nerve sheath tumors (MPNST) pose a significant therapeutic challenge due to high recurrence rates after surgical resection and a largely ineffective response to traditional chemotherapy. An alternative treatment strategy is oncolytic viroimmunotherapy, which can elicit a durable and systemic antitumor immune response and is Food and Drug Administration (FDA)-approved for the treatment of melanoma. Unfortunately, only a subset of patients responds completely, underscoring the need to address barriers hindering viroimmunotherapy effectiveness. Here we investigated the therapeutic utility of targeting key components of the MPNST immunosuppressive microenvironment to enhance viroimmunotherapy's antitumor efficacy in three murine models, one of which showed more immunogenic characteristics than the others. Myelomodulatory therapy with pexidartinib, a small molecule inhibitor of CSF1R tyrosine kinase, and the oncolytic herpes simplex virus T-VEC exhibited the most significant increase in median survival time in the highly immunogenic model. Additionally, targeting myeloid cells with the myelomodulatory therapy trabectedin, a small molecule activator of caspase-8 dependent apoptosis, augmented the survival benefit of T-VEC in a less immunogenic MPNST model. However, tumor regressions or shrinkages were not observed. Depletion experiments confirmed that the enhanced survival benefit relied on a T cell response. Furthermore, flow cytometry analysis following combination viroimmunotherapy revealed decreased M2 macrophages and myeloid-derived suppressor cells and increased tumor-specific gp70+ CD8 T cells within the tumor microenvironment. In summary, our findings provide compelling evidence for the potential to leverage viroimmunotherapy with myeloid cell targeting against MPNST and warrant further investigation.

Malignant peripheral nerve sheath tumor of the descending colon with peritoneal recurrence: A case report

Malignant peripheral nerve sheath tumor of the descending colon with peritoneal recurrence: A case report

Rare case of Lingual Nerve Schwannoma Presenting as Submandibular Area Swelling with Parapharyngeal Extension.

Schwannoma is a rare benign encapsulated nerve sheath tumor which originates from Schwann cells. Generally, schwannoma arising from lingual nerve involves the oral tongue and tongue base in the oral cavity. We report a rare case of lingual nerve schwannoma in a 16-year-old girl with complaint of right-side submandibular swelling for last 4-5 years. A diagnosis was established based on computed tomography (CT scan) and fine needle aspiration cytology (FNAC). CT scan showed tumor involving right submandibular region and superiorly reaching up to parapharyngeal space without any intraoral swelling. She underwent excision under general anesthesia (transcervical approach) without any complication. Per operatively, the tumor was found eccentrically placed with relation to the lingual nerve and lingual nerve fibers were splayed over the tumor. The final histopathological results confirmed the diagnosis of schwannoma.

NFS-20. DECIPHERING CELLULAR CROSSTALK IN PERIPHERAL NERVOUS SYSTEM TUMORS ASSOCIATED WITH NEUROFIBROMATOSIS TYPE 1 THROUGH SINGLE-CELL RNA SEQUENCING

Abstract BACKGROUND Neurofibromatosis Type 1 (NF1) is a genetic disorder characterized by mutations and dysfunctional expression of neurofibromin 1 gene, a critical tumor-suppressor gene. NF1’s complex pathophysiology involves dysregulation of the RAS-MAPK signaling pathway, resulting in sustained MAPK signaling. Among others, the spectrum of clinical features includes low-grade tumors (e.g. plexiform neurofibromas (pNFs)) and malignant peripheral nerve sheath tumors (MPNST). While surgical removal of peripheral nerve tumors is common, total resection is often unattainable. Additionally, approved therapies comprising MEK inhibitors fail to prevent malignization, highlighting the urgent need for novel targets for effective therapies. METHODS To explore novel potential targets across a broad spectrum, we analyzed published scRNA-seq datasets (Kershner et al. 2021, Wu et al. 2022) from human patients, including pNFs and MPNSTs. We further investigated key pathways in vitro with patient-derived cell culture models. RESULTS ScRNA-seq provides insight into complex networks of cell-to-cell interactions that drive the malignant phenotype of cancerous tissues. Due to the rich presence of ECM in NF1 tumors we aimed to investigate cell types contributing to key extracellular matrix (ECM) components and associated signaling pathways. Analysis of 19 NF1 tumor samples revealed consistent presence of Schwann cells (SCs), fibroblasts, endothelial cells, and immune cells. Proliferating cells were found in MPNSTs, while pericytes were exclusive to pNFs. We compared secreted and ECM signaling between the cell types of both tumors. Our analysis discovered, among other findings, collagen signaling, highlighting fibroblasts as emitters and SCs as receivers. We further confirmed these findings through culturing of NF1-derived cells in vitro with and without collagen, observing increased cell proliferation in the presence of collagen. Further experiments and analyses are ongoing. CONCLUSIONS The emphasis on ECM and signaling adds depth to our understanding of NF1 pathogenesis and suggests potential therapeutic targets.

HGG-17. DECIPHERING GENETICS AND EPIGENETICS OF HIGH-GRADE GLIOMAS WITH BRAF ACTIVATING ALTERATION IS SUPPORTING THE DISCOVERY OF A NEW INTRACRANIAL SARCOMA-LIKE BRAF POSITIVE ENTITY

Abstract BACKGROUND The current WHO classification of Central Nervous System tumors recognizes several glioma types driven by the BRAFV600E mutation. These tumors mostly encompass pediatric low-grade gliomas. Nevertheless, a subset of them behaves as anaplastic gliomas and, currently, the unique predictive criterion linked to anaplasia is an elevated mitotic index (more than 2.5 mitoses/mm2). Histologically, the high-grade gliomas harboring BRAFV600E alteration mostly correspond to WHO grade 3 pleomorphic xanthoastrocytoma, IDH wild-type glioblastoma, entering the WHO grade 4 subset like the epithelioid subtype, and the rarer high-grade gliomas with piloïd features. These tumor types share their histomolecular features making differential diagnoses difficult. In this setting, DNA methylation profiling may be very useful to precise the integrative diagnosis. However, some of those high-grade forms failed in our experience to be classified in any methylation class with v11b4 version of the Heidelberg classifier. METHODS To understand the reasons explaining this standard classification failure, we investigated with multi-omics approaches (epigenetics, next-generation sequencing, RNAseq, proteomics and metabolomics) a well clinical characterized cohort of 17 high-grade pediatric intracranial tumors harboring this mutation. RESULTS Interestingly, almost all tumors show similar morphological features and associated passenger molecular alterations mostly CDKN2A homozygous deletion. When using the new v12.5 brain tumor classifier, the methylation profiling of the 2/17 unclassified tumors was clustering with a new MPNST (Malignant Peripheral Nerve Sheath Tumor) methylation entity. The RNAseq and proteomics analyses were showing a different molecular pattern from standard BRAF-mutated high-grade gliomas, even the clinical, radiological and histomolecular characteristics were comparable. CONCLUSION So, methylation profiling should be part of the mandatory molecular assessments to perform when a BRAF-mutated tumor is seen by neuropathologists. Furthermore, the multiomics analyses helped us to define a specific molecular pattern of this new BRAF-driven entity, where frequency and prognosis need to be determined on another larger series.

ETMR-27. ANTI-ANGIOGENIC METRONOMIC THERAPY OF RARE TUMOURS OF THE CENTRAL NERVOUS SYSTEM

Abstract BACKGROUND Improvement of molecular diagnostics has led to significant changes in the categorization of paediatric brain tumours, unveiling novel tumour entities in the latest 2021 WHO classification of central nervous system (CNS) tumours (5th edition), particularly within the group of rare tumours of the CNS (encompassing rare embryonal and sarcomatous tumours (REST) and gliomas). However, treatment recommendations are currently based on small patient cohorts lacking standardized protocols, with even more limited options for progressive or relapsed disease. METHODS Patients from specialized European oncologic centres diagnosed or reclassified as REST receiving anti-angiogenic therapy after relapse (Medulloblastoma European Multitarget Metronomic Anti-Angiogenic Trial - MEMMAT) will be analysed. RESULTS So far, 14 patients from Austria, Czech Republic, Denmark and France were identified, with molecularly reclassified 4 CNS tumours with BCOR/BCORL1 alteration (CNS BCOR/BCORL1), 4 CNS astroblastomas, MN1-altered (ABM_MN1), 3 embryonal tumours with multi-layered rosettes (ETMR) and 1 DICER1-mutated intracranial sarcoma (CNS DICER1) as well as 2 primitive neuroectodermal tumours (PNETs, reclassification ongoing). Initial histological classifications ranged from ependymoma group 3, ETMR, malignant peripheral nerve sheath tumour (MPNST) to EGFR-positive glioblastoma. In 2 cases categorization was unclear with either anaplastic ependymoma, plexus carcinoma or ETMR. 10 patients received standard MEMMAT protocol (biweekly intravenous Bevacizumab with oral drugs: Celebrex, Thalidomide, Fenofibrate, Cyclophosphamide/Etoposide alternating and intrathecal Etoposide and Cytarabine). In 4 cases therapy was modified with an individualized metronomic treatment regimen. CONCLUSION Therapy at initial diagnosis, duration of relapse-treatment, clinical as well as radiological response, overall survival, progression-free survival and molecular hallmarks will be presented.

NFS-30. ADJUVANT MEK INHIBITION TO PREVENT REBOUND GROWTH FOLLOWING PARTIAL RESECTION OF PLEXIFORM NEUROFIBROMAS

Abstract BACKGROUND Plexiform neurofibromas (PNs) are benign peripheral nerve sheath tumors that occur in patients with neurofibromatosis type I. These tumors can cause significant morbidity leading to functional impairment, pain, and disfigurement. Management of PNs is challenging. Complete surgical resection is often not possible due to tumor growth along vital structures, and rebound growth is frequently experienced following subtotal resection (STR) of PNs. The mitogen-activated protein kinase (MAPK) pathway has been implicated in the growth of PNs, and the use of MAPK enzyme (MEK1/2) inhibitors has been shown to be an effective therapy in the treatment of PNs. Herein, we described our institutional experience using a short course of adjuvant MEK1/2 inhibitors in the treatment of pediatric patients with PNs following STR to prevent rebound growth. METHODS A single-institution retrospective record review of pediatric patients who underwent STR of their PN. RESULTS A total of 35 patients with 39 separate PNs had STR of their PNs. Fourteen PNs were treated with resection alone and 25 PNs were treated with a six-month course of adjuvant MEK1/2 inhibitors following STR. The number of patients requiring additional treatment with surgical resection or medical therapy was 11 of 14 patients (79%) in the resection only group and 6 of 25 patients (24%) in the adjuvant MEK1/2 inhibitor group. The mean time to additional treatment for the resection only group was 22 months, and the mean follow-up time for patients receiving adjuvant MEK1/2 inhibition was 29 months. Skin rash was the most common adverse effect seen with adjuvant MEK1/2 inhibition, and one patient experienced a dose-limiting thrombus. CONCLUSIONS A short course of MEK1/2 inhibitors following STR of PNs is effective in the short-term in preventing rebound growth when compared to STR alone. Treatment is well tolerated and should be considered as adjuvant therapy in pediatric patients.

OTHR-14. AN ADOLESCENT WITH A RARE SCHWANNOMA LOCALIZATION AND THE IMPORTANCE OF METHYLATION STUDIES

Abstract BACKGROUND Schwannomas are benign nerve sheath tumours, accounting for about 8% of intracranial tumours, with different histologic patterns described. Olfactory nerves are not expected to have Schwann cells, several theories exist about the origin of these tumours. METHODS/RESULTS A 16-year-old boy was admitted to the emergency department due to a first, self-limited, isolated epileptic event. He scored 15 in the GCS and no focal neurological deficits were observed. At that time, he complained about headaches, lasting for 3 months. Brain CT showed a frontobasal heterogeneous mass. MR characterized it as a 43X34X38 mm well-circumscribed mass, with solid and cystic areas, having an intimate relationship with lamina cribosa, with extensive vasogenic oedema surrounding it, causing deviation of adjacent structures. At that time, he was COVID-19 positive. He was submitted to a craniotomy with a transcortical approach, with an apparent total resection. Retrospectively, he became aware of an improved sense of smell after intervention. The histopathological study revealed a tumour composed of sheets and lobules of large, round cells showing immunopositivity for SOX-10 and S100 and with a Ki-67 index of 5-6%. We proceed to a molecular diagnosis, as the morphology was elusive, finding a methylation pattern highly close to those of schwannomas. With this presumptive diagnosis, clinical and radiological follow-up has been done. After two years, he is doing well, without signs of recurrence. CONCLUSIONS Although rare, an olfactory nerve schwannoma should be considered when there is a frontobasal tumour and impaired sense of smell, although in this case, the COVID-19 infection could be responsible for hyposmia. The clinical picture, imaging and histopathology description were not enough to make the diagnosis and, therefore, to plan the post-surgical approach. We emphasize the importance of a comprehensive molecular study, with a methylation classifier, as this tumour exhibits a typical DNA methylation pattern.

Sporadic Hybrid Nerve Sheath Tumour Arising from a Vestibulocochlear Nerve: A rare Case Report

Hybrid peripheral nerve sheath tumors (HPNST) were first included in the 4th edition of the World Health Organization (WHO) Classification of Central Nervous System in 2016. These tumors are a combination of schwannoma and neurofibroma, and are typically found in the limbs, trunk, and soft tissues. In this case report, we present a rare intracranial localization of neurofibroma/schwannoma with histological examination. Our patient was a 36-year-old man without any tumor genetic syndromes. The tumor measured 1.6 × 1.1 cm and was completely excised. The pathology report showed no significant nuclear atypia, mitotic activity, or necrosis. At the time of writing, the patient is alive and well with no recurrence. It is important to note that HPNSTs are usually benign tumors, but can occur in various locations, including the intracranial region. Further studies with a larger number of cases are needed to determine the exact pathogenetic basis of these tumors.

A Case Report On Unusual Mediastinal Mass

A 28-year-old female, a known case of neurofibromatosis 1, presented to the respiratory medicine department with complaints of breathlessness and cough for 2 weeks’ duration. Clinical examination revealed right-sided moderate pleural effusion. Computed tomography (CT) chest revealed a large anterior mediastinal mass with chest wall infiltration. Histopathology showed neoplasm with epithelioid cells, arranged as sheets and interlacing spindle cells with a moderate amount of eosinophilic cytoplasm and inconspicuous nucleoli. Histopathological examination of excised specimen showed a malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation also known as malignant triton tumor. After palliative chemotherapy, later on follow-up, CT-guided biopsy from right side chest wall lesion also showed the same. Because of this rare presentation, we are reporting this case.

Case of the month from Addenbrooke's hospital, Cambridge, United Kingdom: scrotal nerve sheath tumour – a rare presentation of a scrotal mass

Case of the month from Addenbrooke's hospital, Cambridge, United Kingdom: scrotal nerve sheath tumour – a rare presentation of a scrotal mass

Enhanced IL-12 transgene expression improves oncolytic viroimmunotherapy.

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas with unacceptably low cure rates occurring often in patients with neurofibromatosis 1 defects. To investigate oncolytic Herpes Simplex Virus (oHSV) as an immunotherapeutic approach, we compared viral replication, functional activity, and immune response between unarmed and interleukin 12 (IL-12)-armed oncolytic viruses in virus-permissive (B109) and -resistant (67C-4) murine MPNSTs. This study compared two attenuated IL-12-oHSVs with γ134.5 gene deletions (Δγ134.5) and the same transgene expression cassette. The primary difference in the IL-12-oHSVs was in their ability to counter the translational arrest response in infected cells. Unlike M002 (Δγ134.5, mIL-12), C002 (Δγ134.5, mIL-12, IRS1) expresses an HCMV IRS1 gene and evades dsRNA activated translational arrest in infected cells. Our results show that oHSV replication and gene expression results in vitro were not predictive of oHSV direct oncolytic activity in vivo. Tumors that supported viral replication in cell culture studies resisted viral replication by both oHSVs and restricted M002 transgene expression in vivo. Furthermore, two IL-12-oHSVs with equivalent transcriptional activity differed in IL-12 protein production in vivo, and the differences in IL-12 protein levels were reflected in immune infiltrate activity changes as well as tumor growth suppression differences between the IL-12-oHSVs. C002-treated tumors exhibited sustained IL-12 production with improved dendritic cells, monocyte-macrophage activity (MHCII, CD80/CD86 upregulation) and a polyfunctional Th1-cell response in the tumor infiltrates. These results suggest that transgene protein production differences between oHSVs in vivo, in addition to replication differences, can impact OV-therapeutic activity.

Systemic therapy in NF-1 associated malignant peripheral nerve sheath tumors (MPNST).

11583 Background: MPNST are rare sarcomas that have a poor prognosis and are challenging to treat. Around 50% of MPNSTs are associated with NF1, 40% are sporadic, and 10% are radiation-associated. Doxorubicin (D) based chemotherapy (CT) regimens are commonly used in the front-line, and combinations have better response rates than single agents. Response to second-line regimens is not well documented. The objective of this study is to document efficacy of systemic regimens in MPNST as a benchmark for future novel therapeutics in this space. Methods: 72 patients (pts) with NF1-associated MPNSTs in an MD Anderson database were reviewed retrospectively from EMR. Variables collected included demographics, primary MPNST location, localized vs metastatic, and treatments received (+/- radiation, +/-surgery, +/- lines of CT). Responses (progressive disease (PD), stable disease (SD), partial response (PR)) as interpreted by treating physician and radiology reports and time on treatment for 1st and 2nd line chemotherapy regimens were assessed. Cox proportional-hazard regression was used to investigate associations of variables with overall survival (OS: from time of diagnosis to death or last follow-up). Results: Demographic and CT details are provided (Table). The median age at diagnosis was 34.5 yrs (range: 9-71). The most common MPNST location was the trunk (56.94%). D based regimens were the most frequent 1st-line CT (65.7%), and gemcitabine- docetaxel was the most frequent 2nd-line CT (33.3%). In pts with metastases, 74.4% got 1st line, 44.7% 2nd line, 25.5% 3rd line, and 12.7% got 4th line therapy. Median follow-up was 2.46 yrs (IQR 1.24-9.52). The median time on treatment for 1st and 2nd line CT was 110 (IQR 48-153) and 57 (IQR 41-133) days, respectively. In the multivariate COX model for the entire cohort, male sex (HR: 0.35, 95%CI: 0.18-0.68), lower extremity primary (HR: 0.09, 95%CI: 0.02-0.40), and absence of metastases at last follow up (HR: 0.05, 95%CI: 0.02-0.17) were associated with decreased risk of death. Additional analysis on efficacy and survival of the systemic therapy regimens will be presented at the meeting. Conclusions: In this study < 50% pts with advanced NF1 related MPNST made it to 2nd line CT and outcomes were inferior to the predominantly D based 1st line regimens. This highlights an area of high unmet need. [Table: see text]

Contemporary Approach to Neurofibromatosis Type 1-Associated Malignant Peripheral Nerve Sheath Tumors.

Most malignant peripheral nerve sheath tumors (MPNSTs) are clinically aggressive high-grade sarcomas, arising in individuals with neurofibromatosis type 1 (NF1) at a significantly elevated estimated lifetime frequency of 8%-13%. In the setting of NF1, MPNSTs arise from malignant transformation of benign plexiform neurofibroma and borderline atypical neurofibromas. Composed of neoplastic cells from the Schwannian lineage, these cancers recur in approximately 50% of individuals, and most patients die within five years of diagnosis, despite surgical resection, radiation, and chemotherapy. Treatment for metastatic disease is limited to cytotoxic chemotherapy and investigational clinical trials. In this article, we review the pathophysiology of this aggressive cancer and current approaches to surveillance and treatment.

Epidemiological trends and socioeconomic factors in malignant peripheral nerve sheath tumors with rhabdomyoblastic differentiation: A National Cancer Database study.

e23562 Background: Malignant peripheral nerve sheath tumor with rhabdomyoblastic differentiation, also called a malignant triton tumor (MTT) is both a rare and aggressive form of cancer with both the features of peripheral nerve sheath tumors as well as rhabdomyoblasts with high recurrence rates. There is a higher risk of patients with neurofibromatosis type 1 (NF1) developing MTT. Radiation can be used to excise higher grade large MTT, however, chemotherapy still has no consensus on efficacy. Despite the rarity of MTT with rhabdomyoblastic differentiation, increased efforts to understand epidemiological trends could increase overall understanding of the malignancy. Methods: We extracted data from 50 patients diagnosed with MTT(ICD-9561-3) using the 2004-2020 National Cancer Database (NCDB) to perform a retrospective cohort analysis. We focused on various demographic factors including age, sex, race, Hispanic status, income status, educational status, insurance status, facility type and location, distance from facility, and Charleson-Deyo score using descriptive statistics. Regression analysis was used to identify incidence trends. Results: In our study of 50 patients diagnosed with MTT, a majority of the patients were male (62%), identified as White, and were of non-Spanish/non-Hispanic (90%) ethnicity. The average age at diagnosis was 49 years (SD = 20, range = 3-90) most and patients were treated in academic/research facilities (32%) or integrated network cancer programs (18%). Most patients (48%) had private insurance, with a significant number relying on government-funded programs (44%). The majority of patients (88%) underwent surgery as their primary treatment, with 30% having no residual tumor post-surgery. Additional treatments included radiation therapy (38%), chemotherapy (34%) and the most frequent primary site was the retroperitoneum (30%).The average survival time post-treatment was 35 months, with a survival rate of 43% at 2 years, 23% at 5 years, and a 15% at 10 years. Patients qualified for the top quartile of median housing income( $74,063 ≈). Conclusions: This study is the first analysis of patients with MTT, using the NCDB. It fills a gap in our understanding of this rare and aggressive disease. The majority of MTT patients were male, Caucasian, with an average age at diagnosis of 49 years, which supports previous case report descriptions. In addition, this study reveals the socio-economic factors associated with these patients who mostly earned a median income of $74,063 or more, were insured primarily by private insurance or managed programs (48%), and were treated predominantly in academic or research institutions (32%). It is necessary to continue research to further understand the influence of demographic and socio-economic factors on the diagnosis, treatments, and overall survival of patients with MTT.

The efficacy of immune checkpoint inhibitors as a part of multimodality treatment in soft tissue and bone sarcoma in an academic community setting.

e23564 Background: Prior studies have shown response to immune checkpoint inhibitors (ICI) in a variety of sarcoma subtypes, however, much is still unknown about ICI use in specific sarcoma subtypes due to disease rarity. Patients (pts) are often treated with these agents as part of clinical trials, and real world data in the community setting is lacking. The aim of this study is to report real world efficacy and safety of ICI in sarcoma either alone or with radiation (RT) and/or surgery. Methods: A retrospective cohort review was conducted to identify pts with soft tissue and bone sarcoma who were administered ICI at Kellogg Cancer Center at NorthShore University HealthSystem/Endeavor Health. Pts who received ICI as part of a clinical trial were excluded. Results: A total of 29 pts receiving ICI were identified. Pts had a median of 1 prior systemic therapy. ICI included pembrolizumab (n = 23), nivolumab (n = 5), and ipilimumab/nivolumab (n = 1). Treatment was discontinued in 28 pts due to disease progression (n = 18), toxicities (n = 3), death (n = 2), and maximal response (n = 5). One patient is still undergoing treatment. Median progression-free survival (PFS) was 4.9 months. Median overall survival (OS) was 14 months. Overall response rate (ORR) is 31%. Median duration of response was not reached (44+ months). Complete response (CR) (n = 5) reported in 3 pts with undifferentiated pleomorphic sarcoma (UPS), 1 pt with SMARCA4 deficient undifferentiated sarcoma, and 1 pt with dedifferentiated chondrosarcoma. Partial response (PR) (n = 4) reported in 1 pt with UPS, 1 pt with dedifferentiated liposarcoma, 1 pt with high grade spindle sarcoma of bone, and 1 pt with malignant peripheral nerve sheath tumor. Of those pts with a CR, 2 patients received only pembrolizumab, 1 pt was administered concomitant RT, and 2 pts had administered concomitant surgery. Of the pts who had PR, 3 were also treated with concomitant RT. Grade 3 immune related adverse effects were reported in 5 of the 29 patients. Of these patients, 2 had documented CR and 3 documented PR. Conclusions: This study expands on the real world efficacy of ICI in a variety of sarcoma subtypes. CR and PR rates in this setting were high, and responses were durable, although selection bias for treatment may have played a role. This data supports the treatment of metastatic sarcoma with ICI, especially with concomitant RT and surgery, in a variety of subtypes.

Schwannomas: Experience from a single center reference in Peru.

e14043 Background: Schwannomas are nerve sheath tumors that originate in Schwann cells. They are usually solitary and sporadic and manifest on peripheral, spinal or cranial nerves. It is the most common type of benign peripheral nerve tumor in adults. These tumors represent a diagnostic challenge due to their rarity and difficult differential diagnosis. Our objective was to determine the clinical and pathological characteristics, as well as the therapeutic management of patients with Schwannoma admitted to our institution over a period of time. Methods: A retrospective, cross-sectional and descriptive study was carried out on the cases of patients with Schwannoma over 14 years of age, diagnosed at the National Institute of Neoplastic Diseases from 2009 to 2023. Medical records and pathology reports were reviewed. Results: A total of 225 patients were diagnosed with schwannoma on anatomopathology. Median age was 44 years, with a range of 15 to 92 years. 135 (60%) patients were female and 90 (40%) male, with a ratio of 1.5:1. 19 (8.4%) patients had a second cancer before or after the diagnosis of schwannoma. 6 (2.66%) patients were previously diagnosed with neurofibromatosis. According to anatomical origin: 27 (12%) patients had schwanommas of the abdominal region, 36 (16%) of the head and neck, 42 (18.66%) of the spinal cord, 17 (7.55%) of the extremities, 83 ( 36.88%) of the intracranial region and 20 (8.88%) of the thorax. At the intracranial level, 71 patients had location at the cerebellopontine angle, 5 at the orbital level, 2 at the level of the cerebellum and 5 in another location. At the abdominal level, 13 patients had a retroperitoneal location, 8 at the gastric level, 2 at the renal level and 4 in another location. In 130 patients we can obtain the ki67, median score was 2% (1-50%). Regarding treatment, 156 (69.33%) patients underwent surgery, and 42 (18.66%) patients received radiation treatment. During their follow-up, only 5 (2.22%) patients had local recurrence. Conclusions: Schwannomas are rare benign tumors. In many cases, its suspected diagnosis is difficult due to its similarity to other tumors that must be part of the differential diagnosis. Its treatment is surgical, with the objective of complete macroscopic resection. Radiotherapy is a complementary treatment in case of residual disease.

A Case of Giant Malignant Peripheral Nerve Sheath Tumor of Neck

Malignant peripheral nerve sheath tumor (MPNST) is an extremely rare sarcoma of soft tissue. It is locally invasive, frequently recurred and metastasizes distantly, therefore has a very poor prognosis. the most involved sites are human body and extremities, and MPNST occurs and involved very rarely in the parapharynx of neck. MPNST does not react to radiotherapy and chemotherapy, therefore complete surgical resection is the most important treatment. Since immunohistochemical staining is essential for the final diagnosis, it is common to be confirmed after surgery. We report a case of giant MPNST without symptom in the head and neck involving the right parapharynx with multiple distant metastases in a 74-year-old patient on a review of the literature.

Malignant melanotic schwannoma of the cervical spinal cord: a case report

Spinal cord malignant melanotic schwannoma (MMNST) is a rare central nervous system tumor that originates from the spinal cord or spinal myelin sheath cells and can produce melanin. This type of tumor is usually highly aggressive and malignant, with a poor prognosis. The clinical manifestations of spinal cord MMNST are mainly pain, paresthesia, muscle weakness, muscle atrophy, etc., and symptoms of spinal cord compression, such as intestinal and bladder dysfunction, paraplegia, etc. Early detection of tumor lesions can facilitate tumor removal, improve patients’ quality of life, and prolong patients’ survival. In this case report, a 27-year-old young woman was diagnosed with MMNST of the cervical spinal cord due to weakness of her limbs in our hospital, and underwent surgical resection. The patient’s limbs returned to normal after surgery. It is worth mentioning that the patient visited our hospital 7 months ago for “right upper limb pain for 3 days” and was diagnosed with a cervical spine space-occupying lesion at the same position this time, but the pathology report was “hemosiderosis”. This case report aims to raise awareness of the problem of spinal cord MMNST and contribute to greater knowledge of this rare tumor.