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PubMed2005

Subtotal and total resection of superficial plexiform neurofibromas of face and neck: four case reports.

INTRODUCTION: Plexiform neurofibromas are benign tumours of the peripheral nerves and connective tissue. They develop most often in patients with neurofibromatosis type 1 (NF1) and often grow continuously. Removal of plexiform neurofibromas is usually unsatisfactory because the network-like growth of these tumours often involves multiple nerve fascicles and other adjacent tissues. It has been previously shown that magnetic resonance tomography can distinguish the growth patterns of plexiform neurofibromas into three different categories: superficial, displacing and invasive. PATIENTS AND METHODS: Three cases are described with successful subtotal resections of superficial plexiform neurofibromas, and one case with total resection following the diagnosis of tumour subtype using magnetic resonance imaging (MRI). RESULTS: There was a significant, lasting improvement in appearance which demonstrates that surgical intervention in the case of superficial plexiform neurofibroma is valuable. CONCLUSION: Careful classification of plexiform neurofibroma by means of MRI provides valuable information for the surgical management of patients. It enables the distinction to be drawn between this subtype and the other two subtypes of plexiform neurofibromas.

Adolescent↗
PubMed2001

Tumorigenic properties of neurofibromin-deficient neurofibroma Schwann cells.

Dermal and plexiform neurofibromas are peripheral nerve sheath tumors that arise frequently in neurofibromatosis type 1. The goal of the present study was to examine the tumorigenic properties of neurofibromin-deficient human Schwann cells (SCs) that were found to represent a subset of SCs present in approximately half of the total neurofibromas examined. Highly enriched SC cultures were established from 10 dermal and eight plexiform neurofibromas by selective subculture using glial growth factor-2 and laminin. These cultures had low tumorigenic potential in classical in vitro assays yet several unique preneoplastic properties were frequently observed, including delayed senescence, a lack of density-limited growth, and a strong propensity to spontaneously form proliferative cell aggregates rich in extracellular matrix. Western blot analysis failed to detect full-length neurofibromin in any of the neurofibroma SC cultures, indicating that neurofibromin-deficient SCs had a substantial growth advantage. Immunohistochemical staining of the originating tumors showed the majority were comprised principally of neurofibromin-negative SCs, whereas the remainder contained both neurofibromin-negative and neurofibromin-positive SCs. Lastly, engraftment of neurofibromin-deficient SC cultures into the peripheral nerves of scid mice consistently produced persistent neurofibroma-like tumors with diffuse and often extensive intraneural growth. These findings indicate that neurofibromin-deficient SCs are involved in neurofibroma formation and, by selective subculture, provide a resource for the development of an in vivo model to further examine the role of these mutant SCs in neurofibroma histogenesis.

Adolescent↗
PubMedDate not supplied

[Melanotic neurofibroma].

BACKGROUND: Melanotic neurofibromas are rare tumours. The clinical and histological diagnosis is often difficult to make. CASE REPORT: A 41 year-old woman with type-1 neurofibromatosis presented with an old, large (16 cm by 6 cm) pigmented tumour on her left arm. It was initially considered to be a congenital naevus. Partial surgical resection was performed. Histological examination showed a loose proliferation of spindle-cells within the dermis and subcutaneous layers, with multiple foci of melanin-laden cells but no mitotic figures or atypical cells. There was no melanocytic theca. The tumour had immunoreactivity for the S-100 protein, neuron-specific-enolase, neurofilaments, synaptophysin, A-103 and HMB-45. The association of a benign pigmented tumour producing melanin and the presence of Schwann cells and nervous cells, led to the diagnosis of diffuse melanotic neurofibroma. DISCUSSION: Melanotic neurofibromas can occur on their own or be associated with neurofibromatosis. They must be distinguished from classical neurofibromas when pigmentation occurs in the latter. Melanotic neurofibromas usually appear in the second or third decade of life and rarely in childhood. It is worth noting that hairs may overlie a melanotic neurofibroma, mimicking a giant naevus or a neurocristic cutaneous hamartoma. These are the two main differential diagnoses among children. Among adults, the main difficulty is to distinguish melanotic neurofibroma from pigmented dermatofibrosarcoma, because of the clinical and histological similarities between these two.

Adult↗
PubMed2006

Cellular neurofibroma with atypia mimics sarcoma: report of a case with immunohistochemical staining pattern analysis and literature review.

A case of two sporadic cellular neurofibromas with atypia and one widespread hyalinization neurofibroma of the lumbar spine in a 51-year-old man without evidence of neurofibromatosis-1 is reported. Cellular neurofibroma with atypia is an unusual variant. The definite criteria for low-grade and high-grade malignant peripheral nerve sheath tumors as well as cellular neurofibroma are not well defined in the literature. The clinical significance of atypical cellular neurofibroma has rarely been systematically studied. To our knowledge, the concomitance of cellular architecture and cytologic atypia is rarely documented, and this is a rare report of atypical cellular neurofibroma. The recognition of this entity is of great importance to both pathologists and clinicians because atypical cellular neurofibroma is clever at masquerading both histologically and cytologically as a sarcoma; therefore, a precise diagnosis of this variant is essential because of the differences in treatment and clinical behavior between benignancy and malignancy. We also examined the immunohistochemical characteristics of CD34 positive cells and focal high expression of p53 up to 73% encountered in our case. To our knowledge, seldom have series or case reports elucidated this phenomenon.

Antigens, CD34↗
PubMed1990

Angiogenic and invasive properties of neurofibroma Schwann cells.

Neurofibromas are benign tumors from patients with von Recklinghausen Neurofibromatosis (NF1) that are comprised primarily of Schwann cells. These Schwann cells are found both in association with axons and in the extracellular matrix that is prevalent in neurofibromas, and in which fibroblasts are also abundant. An unresolved question has been whether cells in neurofibromas are normal cells or are intrinsically abnormal. We have tested the hypothesis that cells in neurofibromas are abnormal and have shown that neurofibroma Schwann cells, unlike normal Schwann cells, promote angiogenesis in the chick chorioallantoic membrane model system, and invade basement membranes in this system. In contrast, neurofibroma fibroblasts neither promote angiogenic reactions nor invade basement membranes. When injected into nude mice, neurofibroma Schwann cells do not form progressive tumors. These results suggest that NF1 Schwann cells differ from normal Schwann cells, that they are preneoplastic, and that genetic and/or epigenetic changes in Schwann cells may be required for development of peripheral nerve tumors in NF1.

Allantois↗
PubMed2000

Schwann cells harbor the somatic NF1 mutation in neurofibromas: evidence of two different Schwann cell subpopulations.

Neurofibromas are one of the most characteristic features of neurofibromatosis type 1 (NF1), an inherited autosomal-dominant neurogenetic disorder affecting 1 in 3500 individuals worldwide. These benign tumors mainly consist of Schwann cells (SCs) and fibroblasts. Recent evidence demonstrates that somatic mutations at the NF1 gene are found in neurofibromas, but it has not been demonstrated whether SCs, fibroblasts and/or both cell types bear a somatic loss of NF1. We recently established a cell culture system that allows selective expansion of human SCs from neurofibromas. We cultured pure populations of SCs and fibroblasts derived from 10 neurofibromas with characterized NF1 mutations and found that SCs but not fibroblasts harbored a somatic mutation at the NF1 locus in all studied tumors. Furthermore, by culturing neurofibroma-derived SCs under different in vitro conditions we were able to obtain two genetically distinct SC subpopulations: NF1(-/-) and NF1(+/-). These data strongly support the idea that NF1 mutations in SCs, but not in fibroblasts, correlate to neurofibroma formation and demonstrate that only a portion of SCs in neurofibromas have mutations in both NF1 alleles.

Cell Division↗
PubMed2006

Nf1+/- mast cells induce neurofibroma like phenotypes through secreted TGF-beta signaling.

Neurofibromas are common tumors found in neurofibromatosis type 1 (NF1) patients. These complex tumors are composed of Schwann cells, mast cells, fibroblasts and perineurial cells embedded in collagen that provide a lattice for tumor invasion. Genetic studies demonstrate that in neurofibromas, nullizygous loss of Nf1 in Schwann cells and haploinsufficiency of Nf1 in non-neuronal cells are required for tumorigenesis. Fibroblasts are a major cellular constituent in neurofibromas and are a source of collagen that constitutes approximately 50% of the dry weight of the tumor. Here, we show that two of the prevalent heterozygous cells found in neurofibromas, mast cells and fibroblasts interact directly to contribute to tumor phenotype. Nf1+/- mast cells secrete elevated concentrations of the profibrotic transforming growth factor-beta (TGF-beta). In response to TGF-beta, both murine Nf1+/- fibroblasts and fibroblasts from human neurofibromas proliferate and synthesize excessive collagen, a hallmark of neurofibromas. We also establish that the TGF-beta response occurs via hyperactivation of a novel Ras-c-abl signaling pathway. Genetic or pharmacological inhibition of c-abl reverses fibroblast proliferation and collagen synthesis to wild-type levels. These studies identify a novel molecular target to inhibit neurofibroma formation.

Animals↗
PubMed2000

Evaluation of (18)fluorodeoxyglucose positron emission tomography ((18)FDG PET) in the detection of malignant peripheral nerve sheath tumours arising from within plexiform neurofibromas in neurofibromatosis 1.

OBJECTIVES: The ability of (18)fluorodeoxyglucose positron emission tomography ((18)FDG PET) to detect malignant change in plexiform neurofibromas from patients with neurofibromatosis 1 (NF1) was evaluated. METHODS: Eighteen NF1 patients who presented with pain, increase in size, or neurological deficit associated with a plexiform neurofibroma were assessed. Magnetic resonance imaging determined the site and extent of the lesion. Qualitative(18)FDG PET was performed and the standard uptake value (SUV) measured the regional glucose metabolism. Histological confirmation of the diagnosis was obtained in 10 patients. RESULTS: Twenty three plexiform neurofibromas were detected in 18 patients. Seven malignant peripheral nerve sheath tumours, four high grade and three low grade tumours, occurred in five patients. In one patient the clinical and radiological characteristics of the tumour suggested malignancy, but histology was inconclusive. Fifteen benign plexiform neurofibromas were identified in 12 patients and these findings were confirmed histologically in five lesions from four patients. Ten plexiform neurofibromas occurring in eight patients were considered benign on(18)FDG PET and the patients did not undergo surgery. They remained stable or their symptoms improved on clinical follow up (median 9 months). The results of qualitative (18)FDG PET were interpreted as indicating that 13 plexiform neurofibromas were benign and 10 were malignant. No malignant tumours were classified as benign, but two benign tumours were reported as malignant. The SUV was calculated for 20 tumours and was significantly higher in five malignant tumours 5.4 (SD 2.4), than in 15 benign tumours 1.54 (SD 0.7), p=0.002. There was an overlap between benign and malignant tumours in the SUV range 2.7-3.3. CONCLUSIONS: (18)FDG PET is helpful in determining malignant change in plexiform neurofibromas in NF1. Increased separation between benign and malignant lesions could be obtained by calculating the SUV at about 200 minutes after injection of (18)FDG, when the peak activity concentration is obtained in malignant tumours.

Adolescent↗
PubMed2005

Plexiform neurofibroma of the uterine cervix: a case report and review of the literature.

The female genital system is rarely affected in von Recklinghausen neurofibromatosis. The vulva is the most frequent genital location, but vaginal, cervical, uterine, and ovarian neurofibromas have rarely been reported. We describe a case of plexiform neurofibroma affecting the uterine cervix in a patient with chronic pelvic pain and menorrhagia who had multiple cutaneous neurofibromas and 1 large paraspinal neurofibroma. A small plexiform neurofibroma, which was not grossly visible, was confined to the uterine cervix and coexisted with a uterine leiomyoma and adenomyosis. There were no neurofibromas in the myometrium, fallopian tubes, or ovaries. Plexiform neurofibroma is a neoplasm that should be considered in the differential diagnosis of spindle cell neoplasms of the uterine cervix, especially in specimens from patients with neurofibromatosis.

Actins↗
PubMed1989

Mast cell and lymphoreticular infiltrates in neurofibromas. Comparison with nerve sheath tumors.

Cellular heterogeneity produced by non-Schwannian elements may distinguish neurofibromas from other Schwann cell neoplasma and contribute to a different tumor biology. The present study compared cell counts of mast cells, T and B lymphocytes, and macrophages in 32 neurofibromas with those in 27 schwannomas, 9 malignant nerve sheath tumors, and 17 traumatic neuromas. Immunohistochemical and histochemical analyses were performed on formalin-fixed, paraffin-embedded tissues using two monoclonal antibodies against B-lymphocyte epitopes (LN-1 and LN-2), one monoclonal antibody against T-lymphocyte epitopes (UCHL-1), one polyclonal antibody recognizing alpha 1-antichymotrypsin (ACT), a macrophage/histiocytemarker, and toluidine blue O stains. Neurofibromas contained relatively high concentrations of mast cells significantly greater than the concentrations in other neoplastic or reactive nerve sheath tumors. Most neurofibromas also displayed moderate concentrations of LN-2 immunoreactive cells, similar to the concentrations in traumatic neuromas and not statistically different from cell counts in other tumor types. Limited, variable LN-1 and UCHL-1 immunoreactive infiltrates were detected in neurofibromas and some peripheral schwannomas. Rare or moderate ACT immunoreactivity was detected in the majority of neurofibromas, in contrast with the absence, or rare appearance, of ACT immunostaining in cranial and peripheral nerve schwannomas and moderate numbers of immunoreactive cells in many malignant nerve sheath tumors. Mast cells are an important cellular marker of neurofibromas and may participate in the pathogenesis of these neoplasms.

Antibodies, Monoclonal↗
PubMed1995

[Exclusive nodular plexiform neurofibroma. An unusual case of neurofibromatosis type 1].

INTRODUCTION: Type 1 neurofibromatous tumours (NF) are benign skin tumours which include cutaneous, subcutaneous and plexiform neurofibromas. Plexiform neurofibromas are either diffuse or nodular, the latter form being much more frequent. CASE REPORT: We observed a particular form of neurofibroma in an 18-year-old patient who developed large deep subcutaneous which histology examination revealed to be exclusively nodular plexiform neurofibromas. The patient also had 6 café au lait spots leading to the diagnosis of sporadic NF 1. He did not have acoustic neuronoma, schwannoma or posterior cataract, eliminating NF 2. COMMENTS: In NF 1, subcutaneous neurofibromas develop in 5 p. 100 of the patients. These lesions are termed nodular plexiform neurofibromas when they form long formations along nerve branches. The exclusive nature of the nodular plexiform neurofibromas in our case was exceptional. It could be hypothesized that the particular phenotype in our patient might correspond to a particular anomaly of the NF 1 gene.

Adolescent↗
PubMed1994

Factor-XIIIa-positive cells in normal peripheral nerves and cutaneous neurofibromas of type-1 neurofibromatosis.

Cutaneous neurofibromas consist of heterogenous cell populations including Schwann cells, perineurial cells, and fibroblastlike cells. However, the histogenesis of neurofibromas, particularly the origin and nature of the fibroblastlike cells, is still controversial. Recently, cells containing blood coagulation factor XIIIa have been reported in cutaneous neurofibromas, although their identity is uncertain. In this report, by the combination of double immunohistochemical staining and immunoelectron microscopy, we demonstrate that factor-XIIIa-positive cells are distinct from Schwann cells, perineurial cells, endothelial cells, mast cells, and conventional macrophages, but correspond to the fibroblastlike cells in cutaneous neurofibromas. Such factor-XIIIa-positive cells in cutaneous neurofibromas, however, differ from conventional fibroblasts in the strong expression of HLA-DR antigen and lack of prolyl 4-hydroxylase. Similarly, so-called endoneurial fibroblasts and, occasionally, connective tissue cells within perineurium and epineurium in normal peripheral nerve fibers express factor XIIIa as well as HLA-DR antigen. The results suggest that fibroblastlike cells in cutaneous neurofibromas are probably derived from factor-XIIIa- and HLA-DR antigen-positive connective tissue cells in peripheral nerves. The role of such factor-XIIIa-positive cells in the growth and development of cutaneous neurofibromas is discussed.

Actins↗
PubMed2004

Elevated ankyrin G in a plexiform neurofibroma and neuromas associated with pain.

UNLABELLED: Ankyrin G has recently been shown to be responsible for activation of sodium channels in the developing and regenerating axonal membrane. Via this sodium channel mechanism, elevated ankyrin G levels have been linked with spontaneous ectopic hyperexcitability and thus with pain phenomena in nervous tissue. Ankyrin G, a transmembrane, structural protein of the axon, was examined in four conditions: (a) painful plexiform neurofibroma; (b) painful neuroma; (c) non-painful neuromas; (d) normal nerve. Neurofibroma tissue was obtained from an 18-year old male patient who developed an intensely painful, plexiform neurofibroma of the posterior femoral cutaneous nerve and subsequently underwent surgery. Sample proteins were separated by PAGE and labeled with anti-ankyrin G antibodies in a Western blot procedure. RESULTS: The ankyrin G band density (mug) of protein for the painful neurofibroma was 6014 and was 3557 for the painful neuroma as compared to 3041, 1988 and 606 (mean+/-SD=1878+/-1221) for the three non-painful neuromas. Ankyrin G expression in normal nerves (8 specimens from 7 patients) was comparatively less (mean+/-SD=411+/-339). CONCLUSION: Our results may represent the first evidence for abnormally increased levels of ankyrin G protein with painful neurofibromas. Due to ankyrin G's multifunctional role in the development and remodeling of excitable membranes, it can be hypothesized that the significant increase contributes to the development of hyperexcitable axonal membranes in neurofibromas and potentially other peripheral pain conditions.

Adolescent↗
PubMed2005

[Orbito-temporal plexiform neurofibroma: 6 cases].

INTRODUCTION: Orbito-temporal plexiform neurofibroma is characteristic of Von Recklinghausen neurofibromatosis. We report 6 cases of orbito-temporal plexiform neurofibromas and review different aspects of diagnosis, course and treatment. PATIENTS AND METHODS: Six patients, 4 males and 2 females, with orbito-temporal plexiform neurofibromas were treated between 1986 and 2003. Patient age varied between 10 and 29 years (age average=19). Computed tomography and magnetic resonance imaging were performed in all 6 patients. Surgical resection of the neurofibroma was performed in all patients. RESULTS: The tumor was located on the left in 5 cases and on the right in one. Spheno-orbital dysplasia was found in all patients and was associated with fronto-temporal meningoencephalocele and pulsate exophthalmia. Surgical resection enabled reduction of the neurofibroma. Exenteration was performed in all patients because of a nonfunctional eye. Two patients underwent cure of fronto-temporal meningoencephalocelus with reconstruction of the large wing of the sphenoid using an iliac bone graft and a titanium plate. DISCUSSION: Surgery is essential for orbito-temporal plexiform neurofibroma but is usually difficult, particularly when the tumor has developed increasing the risk of hemorrhage. Bony reconstruction is difficult considering the risk of progressive osseous dysplasia. The cosmetic results achieved in this patient were considered good.

Adolescent↗
PubMed2002

Losses in chromosomes 17, 19, and 22q in neurofibromatosis type 1 and sporadic neurofibromas: a comparative genomic hybridization analysis.

Neurofibromatosis type 1 (von Recklinghausen's NF1) is an autosomal dominant disease associated with an increased risk of benign and malignant neoplasia including malignant peripheral nerve sheath tumors (MPNSTs). In this study, we employed comparative genomic hybridization (CGH) to determine changes in the relative chromosome copy number in 24 patients with neurofibromas, including 12 NF1-associated and 12 sporadic cases. Differences in the frequency and distribution of chromosomal imbalances were observed in both NF1-asociated and sporadic neurofibromas. Chromosomal imbalances were more common in NF1-associated tumors than in sporadic neurofibromas. In both groups, the number of losses was higher than the number of gains, suggesting a predominant role of tumor suppressor gene in tumorigenesis. A number of new chromosomal imbalances were noted including chromosomes 17, 19, and chromosome arm 22q, which may be related to oncogenes or tumor suppressor genes in neurofibromas. In NF1-associated neurofibromas, the most frequent losses were found in chromosome 17 (the minimal common regions were 17p11.2-->p13 in nine cases and 17q24-->q25 in six cases) and 19p (19p13.2 in nine cases). In addition, both NF1-associated and sporadic neurofibromas often exhibited losses at chromosome arms 19q and 22q (in NF1 tumors, the minimal common regions were 19q13.2-->qter in seven cases).

Adult↗
PubMed2001

The angiogenic factor midkine is aberrantly expressed in NF1-deficient Schwann cells and is a mitogen for neurofibroma-derived cells.

Loss of the tumor suppressor gene NF1 in neurofibromatosis type 1 (NF1) contributes to the development of a variety of tumors, including malignant peripheral nerve sheath tumors (MPNST) and benign neurofibromas. Of the different cell types found in neurofibromas, Schwann cells usually provide between 40 and 80%, and are thought to be critical for tumor growth. Here we describe the identification of growth factors that are upregulated in NF1-/- mouse Schwann cells and are potential regulators of angiogenesis and cell growth. Basic fibroblast growth factor (FGF-2), platelet-derived growth factor (PDGF) and midkine (MK) were found to be induced by loss of neurofibromin and MK was further characterized. MK was induced in human neurofibromas, schwannomas, and various nervous system tumors associated with NF1 or NF2; midkine showed an expression pattern overlapping but distinct from its homolog pleiotrophin (PTN). Immunohistochemistry revealed expression of MK in S-100 positive Schwann cells of dermal and plexiform neurofibromas, and in endothelial cells of tumor blood vessels, but not in normal blood vessels. Furthermore, MK demonstrated potent mitogenic activity for human systemic and brain endothelial cells in vitro and stimulated proliferation and soft agar colony formation of human MPNST derived S100 positive cells and fibroblastoid cells derived from an NF1 neurofibroma. The data support a possible central role for MK as a mediator of angiogenesis and neurofibroma growth in NF1. Oncogene (2001) 20, 97 - 105.

Adult↗
PubMed2000

Single cell Ras-GTP analysis reveals altered Ras activity in a subpopulation of neurofibroma Schwann cells but not fibroblasts.

Neurofibromatosis type 1 (NF1) is a common genetic disorder characterized by multiple neurofibromas, peripheral nerve tumors containing mainly Schwann cells and fibroblasts. The NF1 gene encodes neurofibromin, a tumor suppressor postulated to function in part as a Ras GTPase-activating protein. The roles of different cell types and of elevated Ras-GTP in neurofibroma formation are unclear. To determine which neurofibroma cell type has altered Ras-GTP regulation, we developed an immunocytochemical assay for active, GTP-bound Ras. In NIH 3T3 cells, the assay detected overexpressed, constitutively activated K-, N-, and Ha-Ras and insulin-induced endogenous Ras-GTP. In dissociated neurofibroma cells from NF1 patients, Ras-GTP was elevated in Schwann cells but not fibroblasts. Twelve to 62% of tumor Schwann cells showed elevated Ras-GTP, unexpectedly revealing neurofibroma Schwann cell heterogeneity. Increased basal Ras-GTP did not correlate with increased cell proliferation. Normal human Schwann cells, however, did not demonstrate elevated basal Ras activity. Furthermore, compared with cells from wild type littermates, Ras-GTP was elevated in all mouse Nf1(-/-) Schwann cells but never in Nf1(-/-) mouse fibroblasts. Our results indicate that Ras activity is detectably increased in only some neurofibroma Schwann cells and suggest that neurofibromin is not an essential regulator of Ras activity in fibroblasts.

Animals↗
PubMed2006

Neurofibroma-associated growth factors activate a distinct signaling network to alter the function of neurofibromin-deficient endothelial cells.

Genetic inactivation of tumor suppressor genes initiates human cancers. However, interaction of accessory cells with the tumor-initiating cell within the microenvironment is often required for tumor progression. This paradigm is relevant to understanding neurofibroma development in neurofibromatosis type I patients. Somatic inactivation of the Nf1 tumor suppressor gene, which encodes neurofibromin, is necessary but not sufficient to initiate neurofibroma development. In contrast, neurofibromas occur with high penetrance in mice in which Nf1 is ablated in Schwann cells in the context of a heterozygous mutant (Nf1+/-) microenvironment. Neurofibromas are highly vascularized, and recent studies suggest that Nf1+/- mice have increased angiogenesis in vivo. However, the function of neurofibromin in human endothelial cells (ECs) and the biochemical mechanism by which neurofibromin regulates neoangiogenesis are not known. Utilizing Nf1+/- mice, primary human ECs and endothelial progenitor cells harvested from NF1 patients, we identified a discrete Ras effector pathway, which alters the proliferation and migration of neurofibromin-deficient ECs in response to neurofibroma-derived growth factors both in vitro and in vivo. Thus, these studies identify a unique biochemical pathway in Nf1+/- ECs as a potential therapeutic target in the neurofibroma microenvironment.

Alleles↗