Neurofibromatosis Type I (NF1) is a rare genetic disorder. NF1 patients frequently develop a benign tumor in peripheral nerve plexuses called plexiform neurofibroma. In the past two decades, tissue-specific Nf1 knockout mouse models were developed using commercially available tissue-specific Cre recombinase and the Nf1 flox mice to mimic neurofibroma development. However, these models develop para-spinal neurofibroma, recapitulating a rare type of neurofibroma found in NF1 patients. The NPcis mouse model developed a malignant version of neurofibroma called malignant peripheral nerve sheath tumor (MPNST) within 3 to 6 months but intriguingly without apparent benign precursor lesion. Here, we revisited the NPcis model and discovered that about 20% display clinical signs similar to Nf1 tissue-specific knockout mice models. However, a systematic histological analysis could not explain the clinical signs we observed although we noticed lesions reminiscent of a neurofibroma in a peripheral nerve, a cutaneous neurofibroma, and para-spinal neurofibroma on rare occasions in NPcis mice. We also observed that 10% of the mice developed a malignant peripheral nerve sheath tumor (MPNST) spontaneously, coinciding with their earring tag identification. Strikingly, half of the sciatic nerves from NPcis mice developed plexiform neurofibroma within 1-6 months when intentionally injured. Thus, we provided a procedure to turn the widely used NPcis sarcoma model into a model recapitulating plexiform neurofibroma.

UNASSIGNED: This summary describes a publication about a study called SPRINT. The SPRINT study included 50 children with neurofibromatosis type 1 (NF1) and plexiform neurofibroma (PN) that could not be removed with surgery. PNs are tumors that grow along nerves and can cause various problems for children, such as pain, changes to appearance, and muscle weakness. In SPRINT, the study team wanted to learn whether a medication called selumetinib was able to shrink the PN caused by NF1 (also known as NF1-related PN), and if shrinking PNs helped relieve children of the problems caused by it. To assess how selumetinib might help, children had scans to measure the size of their PN, completed questionnaires, and had a variety of other tests done by their doctor. Their caregivers also completed questionnaires about their child. The children took selumetinib capsules twice a day on an empty stomach.
UNASSIGNED: The results showed that selumetinib was able to shrink the PN for most children (68%). The results also showed that the problems caused by the children\'s PNs mostly improved while on selumetinib treatment. SPRINT also showed that the side effects of selumetinib were mainly mild and could be managed by doctors.
UNASSIGNED: Before SPRINT, there were not many treatment options for children with NF1 and PN as there were no medications that had been shown to shrink PN, and surgery was not always possible. SPRINT showed that this medication shrinks most PNs and could help children with NF1 and PN. In April 2020, selumetinib was approved by the US Food and Drug Administration (FDA) because of the results of SPRINT. Selumetinib was the first and, as of February 2024, is the only medicine that can be prescribed by doctors to help children with NF1-related PN. Clinical Trial Registration: NCT01362803 (SPRINT) (ClinicalTrials.gov).

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Isolated intraparotid neurofibromas are exceptionally rare and often associated with neurofibromatosis type 1 (NF1). Diagnosing these tumors proves challenging because of the clinical resemblance to primary salivary gland masses. This case report details an 18-year-old with a painful, enlarging parotid mass, diagnosed through fine needle aspiration biopsy (FNAB) revealing myxoid stroma and spindle cells. Magnetic resonance imaging confirmed a plexiform neurofibroma involving the parotid gland and facial nerve. Histopathology validated the diagnosis, emphasizing the importance of cytological and radiological correlation. Notably, the absent NF1 association makes this case unique. Surgical excision with facial nerve reconstruction was performed, highlighting the complexity of managing such rare intraparotid neurofibromas. Awareness of this entity is crucial for accurate diagnosis and appropriate management.

Selumetinib is clinically used for pediatric patients with neurofibromatosis type 1 and symptomatic, inoperable plexiform neurofibromas. Until recently, selumetinib had to be taken twice daily, after 2 hours of fasting and followed by 1 hour of fasting, which could be inconvenient. This population analysis evaluated the effect of low- and high-fat meals on the pharmacokinetic (PK) parameters of selumetinib and its active metabolite N-desmethyl selumetinib. The dataset comprised 511 subjects from 15 clinical trials who received ≥1 dose of selumetinib and provided ≥1 measurable postdose concentration of selumetinib and N-desmethyl selumetinib. A 2-compartment model with sequential 0- and 1st-order delayed absorption and 1st-order elimination adequately described selumetinib PK characteristics. A 1-compartment model reasonably described N-desmethyl selumetinib PK characteristics over time simultaneously with selumetinib. Selumetinib geometric mean area under the concentration-time curve ratio (1-sided 90% confidence interval [CI] lower bound) was 76.9% (73.3%) with a low-fat meal and 79.3% (76.3%) with a high-fat meal versus fasting. The lower bound of the 1-sided 90% CI demonstrated a difference of <30% between fed and fasted states. Considering the flat exposure-response relationship within the dose range (20-30 mg/m2), the observed range of exposure, and the variability in the SPRINT trial, this was not considered clinically relevant.

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A 4-month-old male presented for a large, hypertrichotic brown patch on the upper back with several scattered 0.5-1.5 cm, round to oval, brown macules and patches on the trunk and extremities. The lesion was initially diagnosed as a giant congenital melanocytic nevus based on clinical exam and histopathology with immunohistochemical stains. The patient was later diagnosed with neurofibromatosis type 1, and the lesion on the back developed a \"bag of worms\" texture consistent with a plexiform neurofibroma and found to harbor a pathogenic variant in the NF1 gene. This case highlights the diagnostic challenge of differentiating these lesions and their overlapping clinical and histopathological features.

BACKGROUND: The approval of selumetinib in patients with neurofibromatosis type 1(NF1) and inoperable plexiform neurofibromas (PN) has reshaped the landscape of clinical management of the disease, and further comprehensive evaluation of the drug\'s efficacy and safety is needed.
METHODS: Original articles reporting on the efficacy and safety of elumetinib in patients with NF1 were comprehensively searched in the Pubmed database, Embase database, Cochrane Library, and Web of Science database and screened for inclusion of studies that met the criteria. We pooled the objective response rate (ORR), disease control rate (DCR), disease progression rate (DPR), and the rate of improvement in PN-related complications using meta-analysis. The incidence of drug-related adverse events was also statistically analyzed.
RESULTS: This study included 10 clinical trials involving 268 patients. The pooled ORR was 68.0% (95% CI 58.0-77.3%), the DCR was 96.8% (95% CI 90.8-99.7%) and the DPR was only 1.4% (95% CI 0-4.3%). The pooled improvement rate was 75.3% (95% CI 56.2-90.9%) for pain and 77.8% (95% CI 63.1-92.5%) for motor disorders. Most adverse events were mild, with the most common being gastrointestinal reactions (diarrhea: 62.5%; vomiting: 54.5%).
CONCLUSIONS: Our study demonstrates that selumetinib is effective in patients with NF1 and PN, significantly improving the serious complications associated with PN as well as having tolerable toxicities. Our findings help to increase clinicians\' confidence in applying selumetinib and promote the clinical adoption and benefit of the new drug.

BACKGROUND: Half of the patients with Neurofibromatosis type 1 (NF1) develop one or more tumours called plexiform neurofibromas, which can have a significant impact on Quality of Life (QoL). The PlexiQoL questionnaire is a disease-specific QoL measure for adults with NF1-associated plexiform neurofibromas. The aim of this study was to adapt and validate a Dutch version of the PlexiQoL for the Netherlands.
METHODS: The PlexiQoL was translated using the dual-panel methodology, followed by cognitive debriefing interviews to assess face and content validity. The psychometric properties were evaluated by administering the questionnaire on two separate occasions to a sample of adults with NF1 and plexiform neurofibromas. Feasibility was evaluated by the presence of floor/ceiling effects. Reliability was assessed by evaluating Cronbach\'s alpha coefficient and test-retest reliability, using Spearman\'s rank correlation coefficients. Mann-Whitney U tests were used to check for known group validity. The Nottingham Health Profile (NHP) questionnaire was used as comparator questionnaire to evaluate convergent validity.
RESULTS: The translation and cognitive debriefing interviews resulted in a Dutch version of the PlexiQoL that reflected the original concept and underlying semantic meanings of the UK English version. Forty participants completed the validation survey. The Dutch PlexiQoL demonstrated excellent internal consistency (Cronbach\'s α 0.825) and test-retest reliability (Spearman correlation coefficient 0.928). The questionnaire detected differences in PlexiQoL scores between participants based on self-reported general health and disease severity. Convergent validity was confirmed for relevant NHP subsections.
CONCLUSIONS: The Dutch PlexiQoL demonstrated excellent psychometric properties and can be reliably used to measure plexiform neurofibroma-related QoL in adults with NF1 in the Netherlands.

Plexiform neurofibromas (PNFs) are nerve tumors caused by loss of NF1 and dysregulation of RAS-MAPK signaling in Schwann cells. Most PNFs shrink in response to MEK inhibition, but targets with increased and durable effects are needed. We identified the anaphylatoxin C5a as increased in PNFs and expressed largely by PNF m acrophages. We defined pharmacokinetic and immunomodulatory properties of a C5aR1/2 antagonist and tested if peptide antagonists augment the effects of MEK inhibition. MEK inhibition recruited C5AR1 to the macrophage surface; short-term inhibition of C5aR elevated macrophage apoptosis and Schwann cell death, without affecting MEK-induced tumor shrinkage. PNF macrophages lacking C5aR1 increased the engulfment of dying Schwann cells, allowing their visualization. Halting combination therapy resulted in altered T-cell distribution, elevated Iba1+ and CD169+ immunoreactivity, and profoundly altered cytokine expression, but not sustained trumor shrinkage. Thus, C5aRA inhibition independently induces macrophage cell death and causes sustained and durable effects on the PNF microenvironment.