Neurofibromatosis Type 1 with a Giant Diffuse Plexiform Neurofibroma Invading the Liver

To the editor, Neurofibromas are relatively common benign tumors that are composed of neuromesenchymal cells, including Schwann cells, perineurial cells, fibroblast and mast cells. Multiple neurofibromas are found as part of neurofibromatosis type I (von Recklinghausen's disease) and neurofibromas are evenly distributed over the body surface. However, as a solitary lesion, a neurofibroma is not associated with neurofibromatosis type I and is common in young adults without a gender preference. Neurofibromas have been known to exhibit a predilection for the trunk and head compared to other body surfaces1. However, in 1949 Herzog2 first reported a plantar neurofibroma in a case of von Recklinghausen's disease. It has been thought that neurofibroma rarely occurs on the palm or sole of the hands or feet. Yamamoto et al.3 reported a plantar neurofibroma as a rare case that was not associated with neurofibromatosis type I. There has been a report of a solitary palmar neurofibroma as a rare case4. Other solitary neurofibromas in uncommon sites have been reported on the male breast5 and the subungual area6-10. In order to investigate the commonly affected sites of solitary neurofibromas, we reviewed the medical records of patients diagnosed with solitary neurofibroma between January 2005 and June 2010. There were 8 patients with solitary neurofibroma and these patients were otherwise healthy. The mean age of the patients was 54-years and the disease duration of solitary neurofibromas ranged from several months to several decades (Table 1). None of the patients had a personal or familial history of neurofibromatosis type I or cafe-au-lait patches. The histopathologic examinations, including S100 stains, were done in all cases for making the differential diagnosis. The histopathologic examination showed unencapsulated tumors in the dermis and the tumors were composed of a fine fibrillary lattice of haphazardly arranged slender spindle cells that showed S100 positivity. As was previously known, there was no gender difference. Interestingly, tumors on the palm and sole, which are considered to be uncommon sites of solitary neurofibroma, were observed in each case (Fig. 1A, B). There was also a case of solitary neurofibroma on the lower lip (Fig. 1C). We believe that these results necessitate the investigation of predilection sites of neurofibromas. Fig. 1 (A) A solitary, dome-shaped papule on the right sole in case No. 4. (B) A 0.5×0.5 cm sized, soft, dome-shaped papule on the left palm in case No. 7. (C) An obliquely arranged, 1×3 cm sized, rubbery nodule on the lower lip in case No. 8. ... Table 1 Gender, age, disease duration and locations of solitary neurofibromas (2005~2010) A previous report evaluated the electron microscopic findings of a solitary subungual neurofibroma, and the electron microscopic findings of a solitary neurofibroma on an exceptional location were in no way inconsistent with those of a neurofibroma on the commonly involved sites6. The histologic findings of our patients were also typical for neurofibroma regardless of the body locations of the tumors. Although several cases of solitary neurofibromas on uncommon sites have been reported, we concluded that neither a predilection site of neurofibroma nor an uncommon site exists for solitary neurofibromas. In our study, the mean age of patients with a solitary neurofibroma (54-years-old) was older than the previously reported age of young adults1. The pathogenesis of isolated solitary neurofibromas is still unclear and further studies on solitary neurofibroma with a larger number of cases are needed.

Neurofibromatosis type 1 (NF1) is a genetic disease that results from either heritable or spontaneous autosomal dominant mutations in the NF1 gene. A second-hit mutation precedes the predominant NF1 neoplasms, which include myeloid leukemia, optic glioma, and plexiform neurofibroma. Despite this requisite NF1 loss of heterozygosity in the tumor cell of origin, nontumorigenic cells contribute to both generalized and specific disease manifestations. In mouse models of plexiform neurofibroma formation, Nf1 haploinsufficient mast cells promote inflammation, accelerating tumor formation and growth. These recruited mast cells, hematopoietic effector cells long known to permeate neurofibroma tissue, mediate key mitogenic signals that contribute to vascular ingrowth, collagen deposition, and tumor growth. Thus, the plexiform neurofibroma microenvironment involves a tumor/stromal interaction with the hematopoietic system that depends, at the molecular level, on a stem cell factor/c-kit-mediated signaling axis. These observations parallel findings in other NF1 disease manifestations and are clearly relevant to medical management of these neurofibromas.

Neurofibromatosis type 1 (NF1) and type 2 (NF2) are genetically and medically distinct neurocutaneous disorders that are both associated with tumors affecting the central and peripheral nervous systems. NF1 has a frequency of 1 in 3,000, compared with 1 in 30,000 for NF2. Careful surveillance is important for both conditions, to allow early identification and treatment of complications. The most common and important problems in NF1 are cognitive impairment, optic pathway gliomas, plexiform neurofibromas, and orthopaedic issues. Early intervention and tailored educational programs are indicated for learning difficulties. Attention deficit hyperactivity disorder may be amenable to treatment with stimulant medication. A clinical trial is under way to evaluate lovastatin in the treatment of cognitive problems in children with NF1. Chemotherapy with vincristine and carboplatin is the current standard of care for symptomatic optic pathway gliomas, but new agents with improved efficacy are needed. Plexiform neurofibromas may be treated with surgery, but often recur. To date, no medical therapy has proven effective in limiting plexiform neurofibroma growth, but several candidate medications are under consideration in clinical trials. Malignant peripheral nerve sheath tumors may arise in preexisting plexiform neurofibromas, so changes in tumor growth or an increase in pain or focal neurologic deficit should prompt further investigation and early treatment with wide surgical resection, with or without adjuvant chemotherapy or radiotherapy. Specialist surgical intervention may be needed for scoliosis and tibial pseudoarthrosis. In NF2, surgical treatment remains a cornerstone of management for symptomatic progressive vestibular schwannomas, meningiomas, and spinal tumors. Vascular endothelial growth factor inhibitors show promise for the treatment of vestibular schwannomas, with the aim of delaying surgery, and other targeted molecular therapies are becoming available as investigational options. Hearing aids and brainstem and cochlear implants have a role in optimizing functional hearing in some patients. Specialist ophthalmology input should be arranged to monitor for ophthalmologic complications. A coordinated effort is needed to enroll NF1 and NF2 patients in international multicenter clinical trials of promising new pharmacologic agents. Genetic testing is useful for prenatal diagnosis and may be important in understanding individual responses to novel medical therapies in the future. Effective transition to adult services is important, considering the likelihood of further complications in the adult years.

The close association of neurofibromatosis type 1 (NF1) with gliomas raises the question of whether the NF1 gene may be involved in the pathogenesis of sporadic astrocytic brain tumors. However, no frequent mutations within NF1 have been described in these tumors. Recent data on a limited series of gliomas indicate that NF1 expression may even be increased, thereby questioning the role of NF1 as a tumor suppressor in astrocytomas. In the present study, we examined the expression of NF1 in a series of 96 tumors including astrocytomas, meningiomas and plexiform neurofibromas. NF1 RNA transcription levels were compared to those of the reference genes B2M, ACTB and GAPD. The expression of OMGP, which is interposed in the NF1 gene, served as an additional control. NF1 expression did not significantly diverge among different malignancy stages of astrocytomas. As expected, the plexiform neurofibromas showed only very low NF1 expression. A striking finding was the highly variable expression of those genes selected to serve as references. While B2M and ACTB exhibited comparable levels of expression within different grades of astrocytomas and meningiomas, GAPD showed an inverse pattern in these tumors. In conclusion, NF1 expression is strongly reduced in NF1-associated plexiform neurofibromas but not in astrocytic tumors. The significant differences between B2M, ACTB and GAPD transcript levels brings into question the common practice of defining gene expression as a ratio between the transcripts of interest and those of these reference genes.

Neurofibromatosis type 1 (NF1) is an autosomal dominant cancer predisposition syndrome caused by a germline mutation in the NF1 gene. The loss of the second copy of NF1 within Schwann cell precursors (SCPs) contributes to the formation of plexiform neurofibromas (PNs) found in 30-50% of NF1 patients. PNs can progress into malignant peripheral sheath tumors (MPNSTs), an aggressive form of cancer and a leading cause of mortality in NF1 patients. Our lab previously demonstrated frequent chromosome 8 (Chr8) gain in NF1-MPNST patient-derived xenografts (PDX) and patient tumors. To investigate Chr8 gain’s role, we created isogenic NF1-/- iPSC cell lines with and without Chr8 gain. Trisomy 8 fibroblasts were obtained and single-cell cloned to establish wildtype (WT) and Chr8 gain populations. Washington University’s Genome Engineering & Stem Cell Center (GESC@MGI) reprogrammed these cells into human induced pluripotent stem cells (hiPSCs). Using synthetic gRNA and CRISPR/Cas9, NF1 knockout lines were generated. Four iPSC cell lines were differentiated into SCPs, and cell survival and proliferation were assessed using Incucyte cell survival and CellTiter-Glo® Assay. Fluorescence in situ hybridization (FISH) and karyotyping validated the human iPSCs. qPCR revealed high expression of iPSC markers OCT3/4 and SOX2 in all iPSC lines. After differentiation, SCP markers (GAP43 and ITGA4) were upregulated in WT, NF1-/-, and Chr8 gain;NF1-/- SCP lines, demonstrating successful differentiation. Furthermore, Chr8 gain; NF1-/- SCPs displayed enhanced proliferation and increased cell survival compared to WT and NF1-/- SCPs, suggesting improved characteristics in the presence of Chr8 gain. In summary, our research provides insights into Chr8 gain and NF1 loss effects on SCP differentiation, proliferation, and survival. Understanding these molecular mechanisms may contribute to developing targeted therapies for NF1.

Café-au-lait spots and neurofibromas are defining features of neurofibromatosis 1 (NF1), but they vary greatly in number, size, and clinical importance from patient to patient. The cause of this variability is unknown. We tested the hypotheses that development of these lesions is influenced by local or familial factors. The presence or absence of café-au-lait spots, cutaneous neurofibromas, and diffuse plexiform neurofibromas was recorded for each of 10 divisions of the body surface in 547 NF1 patients, including 117 affected individuals in 52 families. We used stratified Mantel-Haenszel tests to look for local associations between the presence of diffuse plexiform neurofibromas, cutaneous neurofibromas, and café-au-lait spots in individual body segments of NF1 patients. We used a random effects model to obtain intrafamilial correlation coefficients for the age-adjusted number of body divisions affected with each of the three lesions. No significant association was observed between the occurrence of cutaneous and diffuse plexiform neurofibromas, between café-au-lait spots and cutaneous neurofibromas, or between café-au-lait spots and plexiform neurofibromas in the same body segment. The correlation among relatives in the number of body segments affected with café-au-lait spots was 0.45 (95% confidence interval [CI] = 0.18-0.71), with cutaneous neurofibromas, 0.37 (95% CI = 0.15-0.55), and with plexiform neurofibromas, 0.35 (95% CI = 0.15-0.57). We conclude that the development of café-au-lait spots, cutaneous neurofibromas, and plexiform neurofibromas are spatially independent in NF1 patients but that the development of all three lesions is influenced by familial factors.

Objective:To explore the impact of plexiform neurofibromas on the lives of adults with neurofibromatosis type 1.Background:Neurofibromatosis type 1 is a complex neurogenetic syndrome that affects many aspects of health and functioning. A common manifestation of neurofibromatosis type 1 is plexiform neurofibromas, non-cancerous tumours that can cause disfigurement, pain and neurologic disability. Patient-reported outcome measures used in this condition have addressed symptoms and functional ability but not how the condition affects patients’ lives, particularly, their ability to meet their human needs.Methods:Unstructured qualitative interviews were conducted with adults with neurofibromatosis type 1–associated plexiform neurofibromas in the United Kingdom and United States. Interviewees were encouraged to describe how plexiform neurofibromas affected their ability to meet their needs. Interviews were audio-recorded and transcribed verbatim. The UK and US transcripts were combined and theoretical thematic analysis was conducted.Results:In all, 42 interviews (United Kingdom = 20, United States = 22) were conducted. Transcripts revealed 696 statements on the impact of plexiform neurofibromas on need fulfilment. Five major themes emerged: appearance, relationships, independence, role fulfilment and pleasure.Conclusion:Neurofibromatosis type 1–associated plexiform neurofibromas have a major effect on individuals’ ability to meet their needs. An understanding of need fulfilment will complement information generated from traditional patient-reported outcome measures, particularly in a multi-faceted syndrome such as neurofibromatosis type 1.

BackgroundNeurofibromatosis type 1 is an autosomal dominantly inherited disorder caused by pathogenic variants in the neurofibromatosis type 1 gene, resulting in a predisposition to multiple tumors. Typical neurofibromatosis type 1-associated tumors include cutaneous and plexiform neurofibromas, optic pathway gliomas, breast cancer, and malignant peripheral nerve sheath tumors. The aim of the study was to report a rare case with multiple neurofibromatosis type 1-unrelated tumors in addition to neurofibromatosis type 1-related ones.Case presentationA 36-year-old Caucasian female patient with neurofibromatosis type 1 had a rare tumor spectrum including ganglioglioma, malignant teratoma, pheochromocytoma, vestibular schwannoma, and meningioma in addition to typical neurofibromatosis type 1 tumors such as cutaneous and plexiform neurofibromas. A pathogenic variant in the neurofibromatosis type 1 gene (c.2446C > T, p.Arg816*) was identified in blood-derived DNA while no pathogenic variant was found in the neurofibromatosis type 2 gene.ConclusionThough rare, multiple neurofibromatosis type 1-unrelated tumors can develop in neurofibromatosis type 1 patients, which demands attention and interdisciplinary management. All related genes should be screened for potential pathogenic variants.

Neurofibromatosis Type 1 (NF1) is a common autosomal dominant disorder characterized by high penetrance, widely variable expressivity and occurrence of specific skeletal changes such as tibial osteopathy (TO). We collected data on patients referred to the Italian Neurofibromatosis Study Group in order to compare clinical features between 49 NF1 patients with TO, and 98 age-matched NF1 patients without TO, and to determine whether the presence of TO is associated with a different risk of developing the typical NF1 complications. We assessed both groups for: age at diagnosis of NF1, gender distribution, family history, gender inheritance, presence of scoliosis, sphenoid wing osteopathy, other skeletal abnormalities, macrocrania, hydrocephalus, plexiform neurofibromas, tumors, optic pathway gliomas, T2H (high-signal intensity areas on T2 weighted brain MRI), epilepsy, headache, mental retardation, cardiovascular malformations, and Noonan phenotype. Patients of both groups were subdivided by gender and re-evaluated for these items. Statistical comparison was carried out between the two groups of patients for each feature. We collected data on type of treatment and on the clinical conditions of NF1-TO patients after follow-up. Patient's age at NF1 diagnosis was significantly younger in NF1-TO subjects compared with NF1 subjects without TO, and the incidence of T2H was significantly reduced in NF1-TO males compared with NF1 males without TO. The presence of TO does not imply that there is an increased risk of developing typical complications of NF1 (e.g., optic pathway glioma, plexiform neurofibroma, etc.), however, it does allow us to make an earlier diagnosis of NF1.

Plexiform neurofibromas (PN) in neurofibromatosis 1 (NF1) can cause substantial morbidities. Clinical trials targeting PN have recently described decreases in PN volumes. However, no previous study has assessed the association between changes in PN volumes and PN-related morbidities. Our objective was to assess if increasing PN volume in NF1 is associated with increasing PN-related morbidity. This is a retrospective review of patients enrolled on the NCI NF1 natural history study with ≥7 years of data available. Morbidities including pain, motor dysfunction, vision loss, and PN-related surgery were assessed at time of baseline PN MRI with volumetric analysis and time of MRI with maximum PN volume. Forty-one patients (median age at baseline 8 y) with 57 PN were included. At baseline, 40 PN had at least 1 PN-associated morbidity. During the observation period, 27 PN required increasing pain medication, and these PN grew faster per year (median difference 8.3%; 95% CI: 2.4, 13.8%) than those PN which did not. PN resulting in motor impairment at baseline (n = 11) had larger volumes compared with those that did not (median difference 461 mL; 95% CI: 66.9, 820). Many NF1 PN were associated with clinically significant morbidity at baseline, highlighting the need for longitudinal morbidity evaluations starting at an early age to capture changes in PN-associated morbidities. Prospective evaluation of standardized patient reported and functional outcomes in clinical trials are ongoing and may allow further characterization of the association of PN volume increase or decrease and clinical changes.

PURPOSE: Plexiform neurofibromas (PNF) are peripheral nerve sheath tumors that cause significant morbidity in persons with neurofibromatosis type 1 (NF1), yet treatment options remain limited. To identify novel therapeutic targets for PNF, we applied an integrated multi-omic approach to quantitatively profile kinome enrichment in a mouse model that has predicted therapeutic responses in clinical trials for NF1-associated PNF with high fidelity. EXPERIMENTAL DESIGN: Utilizing RNA sequencing combined with chemical proteomic profiling of the functionally enriched kinome using multiplexed inhibitor beads coupled with mass spectrometry, we identified molecular signatures predictive of response to CDK4/6 and RAS/MAPK pathway inhibition in PNF. Informed by these results, we evaluated the efficacy of the CDK4/6 inhibitor, abemaciclib, and the ERK1/2 inhibitor, LY3214996, alone and in combination in reducing PNF tumor burden in Nf1flox/flox;PostnCre mice. RESULTS: Converging signatures of CDK4/6 and RAS/MAPK pathway activation were identified within the transcriptome and kinome that were conserved in both murine and human PNF. We observed robust additivity of the CDK4/6 inhibitor, abemaciclib, in combination with the ERK1/2 inhibitor, LY3214996, in murine and human NF1(Nf1) mutant Schwann cells. Consistent with these findings, the combination of abemaciclib (CDK4/6i) and LY3214996 (ERK1/2i) synergized to suppress molecular signatures of MAPK activation and exhibited enhanced antitumor activity in Nf1flox/flox;PostnCre mice in vivo. CONCLUSIONS: These findings provide rationale for the clinical translation of CDK4/6 inhibitors alone and in combination with therapies targeting the RAS/MAPK pathway for the treatment of PNF and other peripheral nerve sheath tumors in persons with NF1.

Neurofibromatosis type 1 (NF1), also known as von Recklinghausen's disease, is an autosomal dominant disorder characterized by multiple café-au-lait macules and cutaneous neurofibromas. Although neurofibromas are common in NF1, involvement of the urinary tract is rare, with the bladder being the most frequently affected site. Urachal neurofibromas are extremely rare, and their diagnosis and management remain challenging due to nonspecific imaging characteristics and their often asymptomatic presentation.We report the case of a 30-year-old man with clinical features of NF1 in whom a 5-cm mass at the bladder dome was incidentally identified on MRI performed during evaluation for spinal cord symptoms. Imaging revealed a cone-shaped mass in the urachal region, and cystoscopy showed no mucosal abnormalities. Urinalysis and urine cytology were unremarkable. A transabdominal needle biopsy confirmed the diagnosis of a neurofibroma. Given the tumor’s size (>5 cm) and deep-seated location in the trunk, both known risk factors for malignant transformation, surgical excision was performed, including resection of the urachus and bilateral umbilical ligaments. Histopathological analysis confirmed a plexiform neurofibroma consistent with NF1. The postoperative course was uneventful, with no evidence of recurrence during 36 months of follow-up.This case highlights the rare presentation of a urachal plexiform neurofibroma in a patient with NF1. To reduce the potential risk of malignant transformation associated with plexiform neurofibromas larger than 5 cm and located in deep trunk regions, accurate diagnosis and timely surgical intervention are essential, even in asymptomatic cases.

<div>Abstract<p><b>Purpose:</b> The hallmark of neurofibromatosis type 1 (NF1) is the onset of dermal or plexiform neurofibromas, mainly composed of Schwann cells. Plexiform neurofibromas can transform into malignant peripheral nerve sheath tumors (MPNST) that are resistant to therapies.</p><p><b>Experimental Design:</b> The aim of this study was to identify an additional pathway in the NF1 tumorigenesis. We focused our work on Wnt signaling that is highly implicated in cancer, mainly in regulating the proliferation of cancer stem cells. We quantified mRNAs of 89 Wnt pathway genes in 57 NF1-associated tumors including dermal and plexiform neurofibromas and MPNSTs. Expression of two major stem cell marker genes and five major epithelial–mesenchymal transition marker genes was also assessed. The expression of significantly deregulated Wnt genes was then studied in normal human Schwann cells, fibroblasts, endothelial cells, and mast cells and in seven MPNST cell lines.</p><p><b>Results:</b> The expression of nine Wnt genes was significantly deregulated in plexiform neurofibromas in comparison with dermal neurofibromas. Twenty Wnt genes showed altered expression in MPNST biopsies and cell lines. Immunohistochemical studies confirmed the Wnt pathway activation in NF1-associated MPNSTs. We then confirmed that the knockdown of <i>NF1</i> in Schwann cells but not in epithelial cells provoked the activation of Wnt pathway by functional transfection assays. Furthermore, we showed that the protein expression of active β-catenin was increased in <i>NF1</i>-silenced cell lines. Wnt pathway activation was strongly associated to both cancer stem cell reservoir and Schwann–mesenchymal transition.</p><p><b>Conclusion:</b> We highlighted the implication of Wnt pathway in NF1-associated tumorigenesis. <i>Clin Cancer Res; 20(2); 358–71. ©2013 AACR</i>.</p></div>

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant genetic diseases with a variety of changes and complications of the peripheral and central nervous system. In this article we discuss the prevalence, clinical manifestations and general recommendations for the treatment of children with NF1. The most common neurological disturbances in NF during childhood are cognitive deficits and specific learning difficulties (up to 80 %). Peripheral cutaneous /subcutaneous neurofibromas are usually present in puberty, while plexiform neurofibromas, as inherited lesions in the first years of life, could remain unrecognized. Incidence of malignant peripheral nerve sheath tumors (neurofibrosarcomas) is higher in NF1 than in the general population, with an estimated value of 2%-5%. The most common brain changes are multiple T2-hyperintensities presented in 43% to 93% of children with NF1 age dependent. They are usually localized in basal ganglia, brainstem and cerebellum. Their clinical importance is still unknown which is why they are called „unidentified bright objects“. Visual pathway gliomas (pilocytic astrocytomas) are the most common brain tumors in children with NF1 with the prevalence of 20%. Second in the range are the brainstem tumors. Aqueductal stenosis is the most common reason for hypertensive hydrocephalus in children with NF1. The medical treatment of neurological complications in children with NF1 does not differ from the treatment of equivalent neurological changes in children without NF1.

The purpose of this study is to determine whether benign whole body tumor volume of plexiform neurofibromas (PNs) is a risk factor for malignant peripheral nerve sheath tumors (MPNST) in individuals with neurofibromatosis type 1 (NF1). Thirty-one NF1 patients with MPNSTs and 62 age- and sex-matched NF1 patients without MPNSTs, who had undergone whole body magnetic resonance imaging (MRI) were analyzed for benign whole body tumor volume. Mann-Whitney U test, Wilcoxon signed ranks test, Fisher's exact test (two-tailed), and logistic regression analysis were used for statistical analysis. Sixteen percent of all patients with MPNST did not have internal PN. The median whole body benign tumor volume in patients with PN was 352.0 mL among the MPNST group and 3.8 mL in the comparison group (p < 0.001). When the patients were stratified by age as younger or older than 30 years (median age of MPNST diagnosis), the median benign whole body tumor volume was 693.0 mL in MPNST patients and 0.0 mL in control patients younger than 30 years (p < 0.001). The mean number of PNs in MPNST patients was 2.8 (range 0-13, median 2.0) and 1.4 (range 0-13, median 1.0) in patients without MPNST (p = 0.001). The risk of MPNST development increased 0.2 % with each additional mL of benign PN volume (adjusted odds ratio [OR] = 1.002, 95 % confidence interval [CI] 1.001-1.003, p = 0.005) and was higher in patients younger than 30 years (adjusted OR = 1.007, 95 % CI 1.002-1.012, p = 0.003). Higher numbers of PNs, larger whole body benign tumor volume, and younger age are important risk factors for MPNST. We identified a subgroup of patients with MPNST without internal PN on MRI and the lack of correlation of MPNST development with tumor burden in older patients. These findings may alter our belief that all MPNSTs arise from pre-existing PNs and suggest that surveillance MRI based on clinical suspicion may be warranted in older patients, respectively.