Giant plexiform neurofibroma in a patient with neurofibromatosis type I

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder primarily affecting the development and growth of nerve cell tissues. Plexiform neurofibroma is considered an uncommon skin tumor. The involvement of the genitourinary tract or the lower limb is rare, with bladder, upper urinary tract and genital involvement reported in decreasing order of frequency. The management of patients with plexiform neurofibroma is not well defined and aiming mostly at controlling symptoms. We present a case of a giant genitourinary plexiform neurofibroma associated with lower limb gigantism in a patient with NF1.

Colocalized cellular schwannoma and plexiform neurofibroma in the absence of neurofibromatosis. Case report

The authors report on a patient without neurofibromatosis Type 1 or 2 (NF1 or NF2) and without evidence of schwannomatosis, who was found to have an unusual combination of nerve sheath tumors-a large cellular schwannoma and multifascicular involvement of a plexiform neurofibroma arising from the same site within the radial nerve and posterior cord of the infraclavicular brachial plexus. This case broadens the spectrum of combined pathological features of nerve sheath tumors. Genetic studies revealed a combined loss of neurofibromin and merlin in both regions and chromosome arm 22q deletion within the neurofibroma component only. The latter finding supports the suggestion that these were two different clonal neoplasms, and is consistent with a collision tumor pattern.

Mesenteric plexiform neurofibroma in an 11-year-old boy with von Recklinghausen disease

We experienced the case of an 11-year-old boy diagnosed as having type 1 neurofibromatosis with intraabdominal and pelvic masses. On physical examination, there were multiple café-au-lait spots larger than 15 mm in diameter scattered over the patient's entire body and axillary freckling, but no cutaneous neurofibromas were present. Lisch nodules were detected in the iris by a slit lamp. A large, firm mobile mass was palpated in the lower abdomen. Abdominal computed tomographic scan showed the hypodense masses in the lower abdomen and pelvic cavity. At laparotomy, a 16 x 9-cm, firm nodular mass along the mesentery of the terminal ileum and ascending colon was found. The mesenteric mass was encasing the superior mesenteric vessels and extending into the serosa of the intestine. The mass was incompletely excised together with affected intestine. However, resection of the rectum could not be performed because of the extensive involvement of the entire mesorectum. Histopathologic study revealed a plexiform neurofibroma involving the mesentery and intestine without evidence of malignant transformation. The postoperative course was uneventful. Ten months after the operation, a magnetic resonance imaging showed no interval change of the mesorectal mass.

Neurofibromatosis 1 and neurofibromatosis 2: a twenty first century perspective

Historically, neurofibromatosis 1 (NF1) has been inextricably linked with neurofibromatosis 2 (NF2). Both are inherited autosomal-dominant neurocutaneous disorders that have high de novo mutation rates and carry a high risk of tumour formation. However, they are clinically and genetically distinct diseases and should be considered as seperate entities. NF1 is a common disease that mainly affects the skin and peripheral nervous system and causes characteristic bony dysplasia. By contrast, NF2 is a rare disorder with a relative paucity of skin manifestations and high-grade malignancy is unusual. Neurological symptoms are the predominant problem and the cardinal sign is bilateral vestibular schwannomas. In this Review, I discuss the pertinent diagnostic, clinical, and genetic symptoms of NF1 and NF2. I also examine the current views on the pathogenesis of these neurocutaneous disorders in the wake of advances in molecular genetics and the development of mouse models of disease.

Molecular profiles of neurofibromatosis type 1-associated plexiform neurofibromas: identification of a gene expression signature of poor prognosis

PURPOSE

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a complex variety of clinical symptoms. The hallmark of NF1 is the development of heterogeneous benign neurofibromas, which may appear as dermal neurofibromas or plexiform neurofibromas. NF1 patients with plexiform neurofibromas are at risk of developing malignant peripheral nerve sheath tumors.

EXPERIMENTAL DESIGN

To obtain additional insight into the molecular pathogenesis of plexiform neurofibromas, we used real-time quantitative reverse transcription-PCR assays to quantify the mRNA expression of 349 selected genes in plexiform neurofibromas in comparison with dermal neurofibromas and patient-matched malignant peripheral nerve sheath tumors.

RESULTS

Thirty genes were significantly up-regulated in plexiform neurofibromas compared with dermal neurofibromas. None were down-regulated. The up-regulated genes mainly encoded transcription factors and growth factors and secreted proteins, cytokines, and their receptors, pointing to a role of paracrine and autocrine signaling defects in the genesis of plexiform neurofibromas. We also identified a gene expression profile, based on MMP9, FLT4/VEGFR3, TNFRSF10B/TRAILR2, SHH, and GLI1, which discriminated those plexiform neurofibromas most likely to undergo malignant transformation.

CONCLUSION

Our study has identified a limited number of signaling pathways that could be involved, when altered, in plexiform neurofibroma development. Some of the up-regulated genes could be useful diagnostic or prognostic markers or form the basis of novel therapeutic strategies.

Plexiform Neurofibromas Express the Transcription Factor Gli1

BACKGROUND

Plexiform neurofibromas occur commonly in individuals with neurofibromatosis type 1 (NF1) and consist of neurofibromatous change in multiple nerve fascicles. Previously, we had observed that both plexiform neurofibromas and normal cutaneous nerves expressed Hedgehogs (Hhs), which are intercellular signaling molecules and regulate growth and patterning during embryonic development, and their receptors. In the present study, we examined the expression of Gli1, a transcription factor which mediates Hh signaling to investigate the activation of Hh signaling in plexiform neurofibromas and normal cutaneous nerves.

METHODS

An antihuman Gli1 antibody was used with a standard immunoperoxidase technique to determine Gli1 expression in 5 specimens of plexiform neurofibromas and 5 specimens of normal cutaneous nerves.

RESULTS

Our results showed Gli1 expression in S-100-positive tumor cells within the involved nerve fascicles in plexiform neurofibromas but not in control normal skins.

CONCLUSIONS

Our findings indicate that the Hh signaling pathway is activated in plexiform neurofibromas.

Subclassification of nerve sheath tumors by gene expression profiling

Nerve sheath tumors are the most common tumors of Neurofibromatosis type 1 (NF1) patients. Dermal neurofibromas develop in nearly all NF1-patients, whereas plexiform neurofibromas are only observed in one-third of the patients. NF1-patients have about a 10% lifetime risk for developing malignant pheripheral nerve sheath tumors (MPNST). The origin of these tumors is thought to be the Schwann cell lacking functional neurofibromin. However, additional genetic alterations are likely to modulate tumor biology and to contribute to individual nerve sheath tumor entities. To gain insight into the molecular events and to determine whether these tumors can be classified according to gene expression profiles, we performed expression analysis applying cDNA array technology. Nine dermal neurofibromas, 7 plexiform neurofibromas, ten MPNST and two MPNST cell cultures were examined. All tumors but 6 sporadic MPNST were obtained from NF1-patients. We detected significant differences in gene expression patterns between neurofibromas and MPNST and between dermal neurofibromas and plexiform neurofibromas. Tumor class prediction agreed in all but one case with histological and clinical classification. NF1-associated and sporadic MPNST could not be distinguished by their gene expression patterns. We present a panel of discriminating genes that may assist subclassification of nerve sheath tumors.

Recent advances in neurofibromatosis type 1

PURPOSE OF REVIEW

The past decade, since the identification of the neurofibromatosis type 1 (NF1) gene, has witnessed great advances in our understanding of the role of the NF1 gene in the molecular pathogenesis of NF1-associated clinical abnormalities. The purpose of this review is to highlight recent advances in defining the molecular etiology of nervous system tumors and learning disabilities.

RECENT FINDINGS

Neurofibromas and optic pathway gliomas result from NF1 inactivation in Schwann cells and astrocytes, respectively, but other cellular factors contribute to tumorigenesis. In addition, malignant progression of plexiform neurofibromas to malignant peripheral nerve sheath tumors requires additional genetic changes, including increased expression of growth factor receptors, molecules that are involved in tumor invasion and metastasis, and inactivation of critical cell cycle regulators. In addition, specific types of NF1 gene mutation may be associated with an increased risk for malignancy in individuals with NF1.

SUMMARY

Research over the past few years has resulted in a detailed understanding of the molecular genetics of benign and malignant tumors affecting individuals with NF1 as well as the development of refined small animal models for these tumors. In addition, clinical studies have begun to define specific subpopulations of patients at risk for cancer and have identified targeted therapies for NF1-associated tumors, based on basic science research advances.

Molecular profiling of malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1, based on large-scale real-time RT-PCR

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a complex range of clinical symptoms. The hallmark of NF1 is the onset of heterogeneous (dermal or plexiform) benign neurofibromas. Plexiform neurofibromas can give rise to malignant peripheral nerve sheath tumors (MPNSTs), and the underlying molecular mechanisms are largely unknown.

Results

To obtain further insight into the molecular pathogenesis of MPNSTs, we used real-time quantitative RT-PCR to quantify the mRNA expression of 489 selected genes in MPNSTs, in comparison with plexiform neurofibromas.

The expression of 28 (5.7%) of the 489 genes was significantly different between MPNSTs and plexiform neurofibromas; 16 genes were upregulated and 12 were downregulated in MPNSTs.

The altered genes were mainly involved in cell proliferation (MKI67, TOP2A, CCNE2), senescence (TERT, TERC), apoptosis (BIRC5/Survivin, TP73) and extracellular matrix remodeling (MMP13, MMP9, TIMP4, ITGB4). More interestingly, other genes were involved in the Ras signaling pathway (RASSF2, HMMR/RHAMM) and the Hedgehog-Gli signaling pathway (DHH, PTCH2). Several of the down-regulated genes were Schwann cell-specific (L1CAM, MPZ, S100B, SOX10, ERBB3) or mast cell-specific (CMA1, TPSB), pointing to a depletion and/or dedifferentiation of Schwann cells and mast cells during malignant transformation of plexiform neurofibromas.

Conclusion

These data suggest that a limited number of signaling pathways, and particularly the Hedgehog-Gli signaling pathway, may be involved in malignant transformation of plexiform neurofibromas. Some of the relevant genes or their products warrant further investigation as potential therapeutic targets in NF1.

Familial segmental neurofibromatosis

Segmental neurofibromatosis is considered to be the result of postzygotic NF1 gene mutations. We present a family in which the proband has generalized neurofibromatosis 1, whereas members of previous generations manifest segmental skin lesions. All, including the clinically asymptomatic grandmother, carry the same haplotype. This is the only case in the literature in which a parent with segmental skin findings has a child with full-blown neurofibromatosis 1 disease. The genetic mechanisms underlying this association are discussed. This family can be further investigated by examination of tissue samples from affected and unaffected sites for mutations.

Congenital glaucoma and neurofibromatosis in a monozygotic twin: case report and review of the literature

We describe a dramatic case of an identical twin presenting at birth with unilateral congenital glaucoma. Because of the suspicion of neurofibromatosis 1 a magnetic resonance image of the neural axis was obtained, which revealed a plexiform neurofibroma with spinal cord impingement. Diagnosis of neurofibromatosis 1 was confirmed by 3 months of age with the emergence of café-au-lait spots. This case was compared with all 19 reports published in the English literature of neurofibromatosis 1 associated with congenital glaucoma. Initial presentation, family history, characteristics ofthe clinical syndrome, and outcome of glaucoma in infants with neurofibromatosis 1 and congenital glaucoma were reviewed. A plexiform neurofibroma of the ipsilateral eyelid was present in eight patients and ipsilateral facial hypertrophy occurred in three patients. Café-au-lait spots appeared between the ages of 5 weeks and 8 years; none of the patients were reported to have café-au-lait spots at birth. Newborns with unilateral congenital glaucoma should raise high suspicion for neurofibromatosis 1 and its associated findings, which might need immediate intervention.

[Elephantiasis of the thoracic wall within the scope of von Recklinghausen neurofibromatosis, case report]

Neurofibromas are benign tumors arising from neuroectodermal tissues. They may occur as solitary lesions, or multiple, in which case they are referred to as neurofibromatosis, or von Recklinghausen's disease. We report about a 17-year-old patient with neurofibromatous elephantiasis located in the lateral aspect of the left hemithorax. CT showed massive chest wall infiltration and retroperitoneal tumor growth, but no abnormalities of the cranium. Our surgical treatment consisted of a two-stage, palliative tumor debulking and defect coverage with a splitthickness skin graft. The operative and postoperative course was uneventful.

Determination of end points for treatment of neurofibromatosis 1

Neurofibromatosis 1 is a progressive disorder that affects multiple systems of the body. Management is currently focused on anticipatory guidance, genetic counseling, and symptomatic treatment of specific lesions, usually through surgery. Insights into pathogenesis of the disorder are beginning to suggest possible mechanisms of treatment, and clinical trials have begun for some types of lesions. The unpredictable natural history and variable phenotype present challenges for clinical trials in neurofibromatosis 1, which will need to be addressed to develop a system for reliable testing of potential therapies.

Therapy for plexiform neurofibromas in children with neurofibromatosis 1: an overview

Plexiform neurofibromas are one of the most common and disabling features of neurofibromatosis 1. Treatment options for patients with plexiform neurofibromas have been limited, with surgery being the primary option for patients with progressive lesions causing significant morbidity. Trials have evaluated other treatment approaches, including the use of antihistamines, maturation agents, and antiangiogenic agents. The design of such trials and entry criteria have been quite variable, and results have been difficult to interpret. As more is understood concerning the molecular genetic underpinnings of plexiform neurofibromas, new avenues of treatment are being explored. Evaluation of clinical trials is challenging because of the unpredictable nature of plexiform neurofibromas and difficulties in measuring objective responses. The use of innovative neuroimaging techniques and other outcome measures may greatly improve the design of trials and evaluation of potential effective agents.

NF1 mutations in neurofibromatosis 1 patients with plexiform neurofibromas

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder caused by genetic alterations of the NF1 gene on 17q11.2. About 30% of NF1 patients develop plexiform neurofibromas (PNFs), which often cause severe clinical deficits. To determine whether there is a certain genotype underlying PNFs or subtypes of PNFs, we screened 42 NF1 patients from 41 families with PNFs for mutations in the NF1 gene. In 33 out of the 41 (80%) unrelated patients NF1 mutations were found, 24 are novel while the other 9 have been described in previous studies. The 33 mutations included 23 nonsense and frameshift, six splice and four missense mutations. The tumors in these patients had various sizes and features/growth characteristics. No correlation was found between the type or location of the NF1 mutations and size, location or feature of the PNFs, suggesting that many types of NF1 mutations can lead to development of PNFs.

Malignant schwannoma of the sciatic nerve originating in a spinal plexiform neurofibroma associated with neurofibromatosis type 1--case report

A 26-year-old man with neurofibromatosis type 1 (NF1) presented with a giant malignant schwannoma of the sciatic nerve. The differential diagnosis of malignant peripheral nerve sheath tumor (MPNST) was based on clinical, radiological, and histological evidence. The tumor apparently originated in a spinal plexiform neurofibroma. The lesion was resected totally without neural damage to the sciatic nerve. However, the tumor recurred within 2 months. The patient died of unknown factors probably associated with the spinal involvement. MPNST associated with NF1 has a poor prognosis due to recurrence or metastasis despite complete macroscopic removal.

NF1 deletions in S-100 protein-positive and negative cells of sporadic and neurofibromatosis 1 (NF1)-associated plexiform neurofibromas and malignant peripheral nerve sheath tumors

Although plexiform neurofibroma (PN) is thought to represent a benign neoplasm with the potential for malignant transformation (malignant peripheral nerve sheath tumor; MPNST), its neoplastic nature has been difficult to prove due to cellular heterogeneity, which hampers standard molecular genetic analysis. Its mixed composition typically includes Schwann cells, fibroblasts, perineurial-like cells, and mast cells. Although NF1 loss of heterozygosity has been reported in subsets of PNs, it remains uncertain which cell type(s) harbor these alterations. Using a dual-color fluorescence in situ hybridization and immunohistochemistry technique, we studied NF1 gene status in S-100 protein-positive and -negative cell subpopulations in archival paraffin-embedded specimens from seven PNs, two atypical PNs, one cellular/atypical PN, and eight MPNSTs derived from 13 patients, seven of which had neurofibromatosis type 1 (NF1). NF1 loss was detected in four of seven PNs and one atypical PN, with deletions entirely restricted to S-100 protein-immunoreactive Schwann cells. In contrast, all eight MPNSTs harbored NF1 deletions, regardless of S-100 protein expression or NF1 clinical status. Our results suggest that the Schwann cell is the primary neoplastic component in PNs and that S-100 protein-negative cells in MPNST represent dedifferentiated Schwann cells, which harbor NF1 deletions in both NF1-associated and sporadic tumors.

Mutations affecting mRNA splicing are the most common molecular defects in patients with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is one of the most common inherited disorders in humans and is caused by mutations in the NF1 gene. To date, the majority of the reported NF1 mutations are predicted to result in protein truncation, but very few studies have correlated the causative NF1 mutation with its effect at the mRNA level. We have applied a whole NF1 cDNA screening methodology to the study of 80 unrelated NF1 patients and have identified 44 different mutations, 32 being novel, in 52 of these patients. Mutations were detected in 87% of the familial cases, but in 51% of the sporadic ones. At least 15 of the 80 NF1 patients (19%) had recurrent mutations. The study shows that in 50% of the patients in whom the mutations were identified, these resulted in splicing alterations. Most of the splicing mutations did not involve the conserved AG/GT dinucleotides of the splice sites. One frameshift, two nonsense and two missense mutations were also responsible for alterations in mRNA splicing. The location and type of mutation within the NF1 gene, and its putative effect at the protein level, do not indicate any relationship to any specific clinical feature of NF1. The high proportion of aberrant spliced transcripts detected in NF1 patients stresses the importance of studying mutations at both the genomic and RNA level. It is possible that part of the clinical variability in NF1 could be due to mutations affecting mRNA splicing, which is the most common molecular defect in NF1.

Allelic loss of the NF1 gene in NF1-associated plexiform neurofibromas

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder with a complex variety of clinical symptoms. Genetic alteration of the NF1 gene on 17q11.2 is the disease. Neurofibromas of the peripheral nervous system are one main manifestation. A variant of neurofibroma is the plexiform neurofibroma which can be found in about 30% of NF1-patients, often causing severe clinical symptoms. In this study, we examined 14 such tumors from 10 NF1-patients for allele loss of the NF1 gene (LOH: loss of heterozygosity) using four intragenic polymorphic markers. Loss of heterozygosity was found in eight tumors from five patients, and suspected in one additional tumor from another patient. This finding suggests that loss of the second allele, and thus inactivation of both alleles of the NF1 gene, is associated with the development of plexiform neurofibromas. The 14 plexiform neufibromas were also examined for mutation in the TP53 gene by screening exons 5 through 8 using temperature gradient gel electrophoresis. No mutation was found in any of the tumors.

[Plexiform neurofibroma and basal ganglia anomaly in Watson syndrome]

A 4 year-old boy was referred for diagnostic reevaluation with known pulmonary valve stenosis. Physical examination revealed multiple cafe-au-lait spots, inguinal freckling and on the right side in supraclavicular region a softly, non-painful tumour. The boy showed a mild mental and language retardation. Ultrasound and MRT demonstrated supraclavicular a plexiform neurofibroma and intracranial increased intensity lesions in basal ganglia and mesencephalon. In our patient, we have diagnosed a Watson-Syndrome, the overlap and differences to neurofibromatosis type I is discussed.

Neurofibromatosis 1 in childhood

Neurofibromatosis 1 (NF1) is an autosomal-dominant disorder with an incidence of approximately 1 in 3,000. The cardinal features of the disorder are cafe au lait spots, axillary freckling, cutaneous neurofibromas, and iris hamartomas (Lisch nodules). Common complications include learning disability, scoliosis, and optic gliomas. Other complications (e.g., peripheral nerve malignancy, bony deformities, and epilepsy) are individually rare. The mainstay of care for patients with NF1 is anticipatory guidance, and the early detection and symptomatic treatment of disease complications. Counseling of patients and their families should provide a realistic overview of possible disease complications, while emphasizing that most individuals with NF1 lead healthy and productive lives. The gene for NF1 has been identified, and future cell biology research will focus on understanding the pathogenetic mechanisms that underly the diverse manifestations of the disorder.