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At least 127 records · Page 7Linked to original sources
PubMed2005

Analysis of somatic NF1 promoter methylation in plexiform neurofibromas and Schwann cells.

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder with the characteristic feature being the neurofibroma. It is believed that both NF1 alleles must be inactivated as the first step in tumorigenesis. However, often the somatic mutations are not identified, suggesting that epigenetic changes such as methylation could account for the "second hit" in some tumors. The literature reports that the region of the NF1 promoter surrounding the transcription start site is completely unmethylated in several normal tissues and some NF1-related dermal and plexiform neurofibromas. We analyzed the methylation state of the NF1 promoter in normal Schwann cells (the cell type clonally expanded in neurofibromas) and in NF1-related plexiform tumor samples with unidentified somatic mutations. In a region of 451 bp surrounding the transcription start site, a low level of methylation was found at several specific cytosines in 12 of 18 tumor samples. Overall, epigenetic silencing through methylation does not appear to be a major mechanism for the second hit. However, this study, which analyzed the largest number of NF1-related plexiform tumors and is the first to include Schwann cell-enriched tumor cultures, detected greater methylation than in any previous reports. This suggests that methylation, especially at potential transcription factor binding sites, is moderately perturbed in some plexiform neurofibromas and should be investigated further.

Cells, Cultured↗
PubMed2005

Plexiform neurofibroma of the cauda equina: case report.

BACKGROUND: Plexiform neurofibromas are rarely found in the cauda equina. The most recent report of a plexiform neurofibroma of the cauda equina noted only 2 previously described cases. CASE DESCRIPTION: To these we add the current case, as well as 2 additional previously published cases. We report the case of a 44-year-old man with a sudden exacerbation of his long-standing lower-back and bilateral leg pain. An intradural lesion was seen on magnetic resonance imaging and he underwent surgery. Intraoperatively, there were swollen nerve roots and tumor insinuating itself between the roots. A biopsy was performed, and pathology findings were consistent with plexiform neurofibroma. CONCLUSIONS: Plexiform neurofibroma of the cauda equina is a rare tumor, with variable manifestations. These tumors are not amenable to complete resection. Surgical treatment consists of either partial resection or biopsy, possibly with dural grafting for decompression.

Adult↗
PubMed2000

Surgical debulking of eyelid and anterior orbital plexiform neurofibromas by means of the carbon dioxide laser.

PURPOSE: To present the carbon dioxide laser as an effective tool for surgical debulking of eyelid and orbital neurofibromas. METHOD: Two patients with neurofibromatosis underwent surgical debulking of their eyelid and orbital plexiform neurofibromas by means of the carbon dioxide laser. RESULTS: Acceptable cosmetic results were obtained with the removal of eyelid and orbital neurofibromas with improved hemostasis and minimal destruction of surrounding tissue when compared with conventional methods of removal. CONCLUSIONS: The carbon dioxide laser may allow significant improvement in the removal of plexiform neurofibromas.

Adult↗
PubMed1992

Bilateral localized orbital neurofibromas.

BACKGROUND: The authors report on a 30-year-old man who presented with progressive bilateral exophthalmos over a 2-year period. FINDINGS: Computed tomography showed large heterogeneous masses in the superior aspect of both orbits. Excisional biopsy via bilateral lateral orbitotomies showed the tumors to be well-circumscribed, relatively avascular, localized neurofibromas. The patient had several features suggestive of multiple endocrine neoplasia type IIB, including Marfanoid habitus, enlarged corneal nerves, thickened lips, and mucosal neuromas. CONCLUSION: Localized neurofibromas are rare in the orbit and, unlike plexiform neurofibromas, are not typically associated with von Recklinghausen's neurofibromatosis. Bilaterality of such localized neurofibromas has not been previously reported. Recognition of ophthalmic lesions suggestive of multiple endocrine neoplasia IIB should prompt evaluation for systemic manifestations of this disorder.

Adult↗
PubMed1999

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.

Adult↗
PubMed1995

Development of a schwannoma within a facial nerve neurofibroma: a case report and literature review.

We report the presence of a schwannoma within a neurofibroma of the intratemporal facial nerve. This neurofibroma recurred 39 years after its first excision in the parotid gland. Although some believe that schwannomas and neurofibromas represent the same entity, these tumors present distinctive histopathologic and clinical characteristics, which are discussed. The extreme rarity of a schwannoma developing within a neurofibroma is underlined. This is the first report of such an association occurring within a cranial nerve.

Cranial Nerve Neoplasms↗
PubMedDate not supplied

Pedal plexiform neurofibroma: review of the literature and case report.

Plexiform neurofibroma typically occurs in the setting of neurofibromatosis type 1, and is included in the diagnostic criteria for neurofibromatosis. Plexiform neurofibromas generally affect larger peripheral nerves and are uncommon in the foot and ankle. While there are several reports of large neurofibromas involving the foot, they have been described on the plantar aspect. We report the first known case of plexiform neurofibroma involving the deep peroneal nerve of the foot. A review of the literature is also presented.

Adult↗
PubMed2006

Neurofibroma of the lingual nerve: a case report.

A neurofibroma of the lingual nerve is a rare clinical finding, the most common lesion site of a lingual neurofibroma being the tongue. In most situations, it is difficult to determine the precise nerve origins. Herein, we report a case of lingual nerve neurofibroma that presented as a submandibular mass, mimicking a submandibular gland tumor or solitary lymphadenopathy. Complete surgical excision of such a lesion for histopathologic examination provides a better treatment and final diagnosis. For a patient presenting with neurofibromatosis and a submandibular mass, a neurofibroma of nerve origin should be considered in the differential diagnosis.

Adult↗
PubMed1996

Subcutaneous diffuse neurofibroma of the neck: a case report.

A case of a rare and unusual variant of neurofibroma, diffuse neurofibroma (paraneurofibroma), in a young patient is presented. The clinical, radiological and histopathological features of this case are reported. The magnetic resonance imaging (MRI) features of the diffuse neurofibroma are comparable with those described in other neurofibromas.

Child↗
PubMed2000

Microsatellite instability and promoter methylation as possible causes of NF1 gene inactivation in neurofibromas.

Neurofibromatosis type 1 (NF1) is a frequent hereditary disorder. One of the characteristic features of this disease is the development of neurofibromas. Since the NF1 gene is supposed to be a tumour suppressor gene, these neurofibromas should develop upon inactivation of both NF1 alleles. So far, mutation and deletion have been found to be involved in NF1 gene inactivation. However, these inactivating mechanisms explain the development of only a limited fraction of analysed neurofibromas. In this study, we investigated microsatellite instability (MSI) and promoter methylation as potential contributors to NF1 gene inactivation. As site-specific methylation in the NF1 promoter inhibits binding of transcription factors Sp1 and CREB, we studied the methylation status of their binding sites in particular. We analysed 20 neurofibromas and three neurofibrosarcomas, but did not find evidence for microsatellite instability or NF1 promoter methylation in any of the tumours. Thus, our data suggest that both microsatellite instability and promoter methylation are unlikely to be the major causes of NF1 gene inactivation in these tumours.

Base Sequence↗
PubMed2003

Liposuction: a less invasive surgical method of debulking plexiform neurofibromas.

BACKGROUND: Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder in humans. The hallmark of NF1 is development of neural tumors. Plexiform neurofibromas are a major source of morbidity associated with NF1. Surgical removal of these particular tumors is associated with a high risk of damage of surrounding vital structures as well as a risk of significant hemorrhage. Surgical debulking of tumors also sometimes leads to extensive scarring, which may be very disfiguring. OBJECTIVE AND METHODS: We report a novel approach to the surgical therapy of plexiform neurofibromas using liposuction in two patients. RESULTS: Debulking of plexiform neurofibromas with liposuction was successful in both patients. Postoperative follow-up 6 months later showed no evidence of tumor regrowth in either case. CONCLUSION: Liposuction may be a preferable surgical method for debulking of superficial plexiform neurofibromas in patients with NF1. This method is less invasive than conventional surgical tumor debulking.

Adolescent↗
PubMed2002

A rare case of a facial-nerve neurofibroma in the parotid gland.

The incidence of solitary neurofibroma of the facial nerve originating in the parotid region is extremely low. We report a case of a solitary neurofibroma in a 30-year-old male, who initially presented with a parotid mass without facial paresis or paralysis. A chain of small nodules had been palpable in the right parotid region for the previous 2-3 years. MRI and CT scans revealed several small ovoid lesions extending from the frontal margin of the parotid gland to the retromandibular region. The lesions were surgically removed. The main trunk of the facial nerve was adherent to the dorsal side of the largest nodule; however, this mass was resected atraumatically. Histopathological examination indicated neurofibroma. The incidence, presentation, diagnosis and surgical treatment of intraparotid neurofibroma are discussed and compared with those of Schwannoma.

Adult↗
PubMed1999

Thoracoscopic resection of intrathoracic vagus neurofibroma.

A thoracoscopic resection of mediastinal neurofibroma originating from the intrathoracic vagus nerve was successfully performed in an 18-year-old female. This report reviews the clinical and morphological features of intrathoracic vagus neurofibroma. Often neurofibroma has multiple lesions and/or multinodular shape. Thoracoscopic resection is a useful treatment for patients with intrathoracic neurofibroma, although careful observation is necessary when performing a radical resection.

Adolescent↗
PubMed1998

[Intra-parotid neurofibroma of the facial nerve].

BACKGROUND: Solitary intraparotid facial neurofibromas are extremely rare. These tumours arise from Schwann cells, in most cases as a manifestation of neurofibromatosis. In an intraparotid localisation, they can mimic other parotideal tumours. Due to their slow growth, they may be clinically inapparent for a long time. CASE REPORT: We present the case of a patient with a right intraparotid neurofibroma originating from the facial nerve. He noted a slight facial weakness for the last three years and dullness over the preauricular area. On operation, all facial nerve branches were incorporated in the tumour mass. A total resection via monitoring technique of facial nerve function was performed. Postoperatively, the patient suffered from an incomplete facial palsy. CONCLUSION: This case highlights particularly the importance of a concise diagnostic work-up of every facial palsy. Precise histological diagnosis is particularly essential because of the different biological behaviour of neurofibromas in contrast to neurinomas. With preoperative facial palsy the chance of facial nerve preservation decreases. Clinical and operative experience with parotid gland neurofibromas shows that recovery of facial nerve defects is mostly incomplete.

Cranial Nerve Neoplasms↗
PubMed2003

Treatment of orbital schwannomas and neurofibromas.

We present an overview of the treatment and clinical outcome of five orbital peripheral nerve tumours, carried out in our centre from 1999 to 2003. The surgical approach was determined by the location and extension of the lesion. Supraorbital orbitotomy was performed in two superiorly located lesions, a transconjunctival approach in one medial, basal, extraconal lesion. A pterional extradural approach was used in two cases with involvement of the apex, superior orbital fissure and cavernous sinus. Three patients were diagnosed as having schwannoma, one as neurofibroma, and one as cystic mixed neurofibroma and schwannoma. One patient suffered from multiple schwannomas [bilateral acoustic schwannomas, cervical schwannomas (NF2)]. One patient showed bilateral orbital neurofibromas, plexiform cutaneous neurofibroma (NF1) and glaucoma due to a coexisting Marfan's syndrome. Local recurrences were not seen after complete resection in all patients. Surgery is the therapeutic goal.

Adult↗
PubMed2006

An absence of cutaneous neurofibromas associated with a 3-bp inframe deletion in exon 17 of the NF1 gene (c.2970-2972 delAAT): evidence of a clinically significant NF1 genotype-phenotype correlation.

Neurofibromatosis type 1 (NF1) is characterized by cafe-au-lait spots, skinfold freckling, and cutaneous neurofibromas. No obvious relationships between small mutations (<20 bp) of the NF1 gene and a specific phenotype have previously been demonstrated, which suggests that interaction with either unlinked modifying genes and/or the normal NF1 allele may be involved in the development of the particular clinical features associated with NF1. We identified 21 unrelated probands with NF1 (14 familial and 7 sporadic cases) who were all found to have the same c.2970-2972 delAAT (p.990delM) mutation but no cutaneous neurofibromas or clinically obvious plexiform neurofibromas. Molecular analysis identified the same 3-bp inframe deletion (c.2970-2972 delAAT) in exon 17 of the NF1 gene in all affected subjects. The Delta AAT mutation is predicted to result in the loss of one of two adjacent methionines (codon 991 or 992) ( Delta Met991), in conjunction with silent ACA-->ACG change of codon 990. These two methionine residues are located in a highly conserved region of neurofibromin and are expected, therefore, to have a functional role in the protein. Our data represent results from the first study to correlate a specific small mutation of the NF1 gene to the expression of a particular clinical phenotype. The biological mechanism that relates this specific mutation to the suppression of cutaneous neurofibroma development is unknown.

Adolescent↗
PubMed1988

Plexiforme neurofibroma of the skin.

Three cutaneous tumors showing massively thickened nerve fascicles, with a myxomatous matrix in a diffuse tumor mass, were studied by light and electron microscopy, immunohistochemically, and with 3H-thymidine autoradiography. Corresponding to plexiforme neurofibroma, these tumors were called plexiforme neurofibroma of the skin and are compared with nerve sheath myxoma (i.e., cutaneous lobular neuromyxoma, bizarre cutaneous neurofibroma, neurothekoma, and others). In the tumors, a high proportion of perineurial cells (30%) could be detected. Compared with results from regenerating nerves, organized traumatic neuroma, and other types of neurofibroma, these findings show that all constituents of normal peripheral nerves, especially Schwann cells and perineurial cells, may be involved in the growth of peripheral nerve sheath tumors. Furthermore, autoradiography demonstrated a high proliferative activity in one of the tumors. The possible clinical relevance of this finding and the question of whether these tumors may bear a higher risk for malignancy will be discussed.

Adolescent↗
PubMed2002

Intratumoral fat in neurofibroma.

Three cases of a solitary neurofibroma showing focal fatty changes are reported. Fatty changes in a neurofibroma are rarely observed and have not been reported, and also, the pathogenesis of neurofibroma has not been clarified. We postulate that the fatty changes in a neurofibroma may be the result of so-called senescent change or chronic injury. The origin of adipose cells may be attributable to fatty infiltration from abutting tissues or to a metaplasia of tumor cells or resident fibroblasts.

Adipose Tissue↗