Comparative pathology of nerve sheath tumors in mouse models and humans.

Despite the progress made in our understanding of the biology of neurofibromatosis (NF), the long-term clinical outcome for affected patients has not changed significantly in the past decades, and both NF1 and NF2 are still associated with a significant morbidity and a decreased life span. A number of NF1 and NF2 murine models have been generated to aid in the study of NF tumor biology and in the development of targeted therapies for NF patients. A single, universal pathological classification of the lesions generated in these murine models is essential for the validation of the models, for their analysis and comparison with other models, and for their future effective use in preclinical treatment trials. For the formulation of a pathological classification of these lesions, the WHO classification of human tumors was used as a reference. However, it was not adopted for the classification of the GEM lesions because of some important differences between the human and murine lesions. A novel classification scheme for peripheral nerve sheath tumors in murine models was therefore devised.

[Neurofibromatoses. Types, classification and diagnostic criteria]. / Nevrofibromatozi. Vidove, klasifikatsiia i diagnostichni kriterii.

According to the worldwide-accepted classification of the neurofibromatoses only neurofibromatosis type 1 (NF1) and neurofibromatosis type 2 (NF2) are well defined. Other described forms of neurofibromatosis are rare. The aim of this paper is to review the contemporary classification and diagnostic criteria of the different types of neurofibromatoses.

The different forms of neurofibromatosis.

In the last two decades our knowledge of the natural history, genetics and management of the different forms of neurofibromatosis has changed. Of the numerical classifications of neurofibromatosis proposed in the past, only neurofibromatosis type 1 (Nf1) and neurofibromatosis type 2 (Nf2) have been shown to be distinct at clinical and molecular levels. Mosaicism has been demonstrated both in patients with Nf1 and in patients with Nf2, and features of segmental or mosaic Nf1 and Nf2 have been defined. The outlying phenotypes and the molecular genetics of other, rarer, types of neurofibromatosis have been delineated: these are hereditary spinal neurofibromatosis, Schwannomatosis, familial intestinal neurofibromatosis, autosomal dominant "cafe-au-lait spots alone", autosomal dominant "neurofibromas alone", Watson syndrome, Noonan/neurofibromatosis syndrome and the so-called syndrome of multiple naevi, multiple schwannomas and multiple vaginal leiomyomas. In this article I will review the different forms of neurofibromatosis, focusing on those aspects that most commonly challenge the neurosurgeon.

Type of mutation in the neurofibromatosis type 2 gene (NF2) frequently determines severity of disease.

The gene predisposing to neurofibromatosis type 2 (NF2) on human chromosome 22 has revealed a wide variety of different mutations in NF2 individuals. These patients display a marked variability in clinical presentation, ranging from very severe disease with numerous tumors at a young age to a relatively mild condition much later in life. To investigate whether this phenotypic heterogeneity is determined by the type of mutation in NF2, we have collected clinical information on 111 NF2 cases from 73 different families on whom we have performed mutation screening in this gene. Sixty-seven individuals (56.2%) from 41 of these kindreds revealed 36 different putative disease-causing mutations. These include 26 proposed protein-truncating alterations (frameshift deletions/insertions and nonsense mutations), 6 splice-site mutations, 2 missense mutations, 1 base substitution in the 3' UTR of the NF2 cDNA, and a single 3-bp in-frame insertion. Seventeen of these mutations are novel, whereas the remaining 19 have been described previously in other NF2 individuals or sporadic tumors. When individuals harboring protein-truncating mutations are compared with cases with single codon alterations, a significant correlation (P < .001) with clinical outcome is observed. Twenty-four of 28 patients with mutations that cause premature truncation of the NF2 protein, schwannomin, present with severe phenotypes. In contrast, all 16 cases from three families with mutations that affect only a single amino acid have mild NF2. These data provide conclusive evidence that a phenotype/genotype correlation exists for certain NF2 mutations.

Germline mutations in the neurofibromatosis type 2 tumour suppressor gene.

The recent identification of the NF2 tumour suppressor gene has enabled large scale screening for pathological mutations in the gene. We have sought germline mutations in the NF2 gene by SSCP and heteroduplex analysis of cDNA and genomic DNA samples followed by cloning and sequencing of mutant alleles. In the present report we describe 11 putative pathological mutations, including five nonsense mutations, three short insertions or deletions causing frameshifts and three missense mutations. Most stop mutations and frameshift mutations were found in individuals expressing a severe phenotype while one of the three missense mutations was associated with a mild phenotype. Four unrelated NF2 patients of the 93 tested were found to have identical nonsense mutations caused by a C to T transition (C169) in a CpG dinucleotide, which is a potential mutational hotspot in the NF2 tumour suppressor gene.

Neurofribroma plexiforme de colon transverso: relato de caso / Large bowel plexiform neurofibroma: a case report

Tumores neurogenicos de colon sao raros na populacao geral, mas podem ocorrer em 11 a 25 por cento dos pacientes com doenca de von Recklinghausen . Apresentamos o caso de uma paciente de 24 anos de idade com neurofibroma plexiforme do intestino grosso cuja manifestacao inicial caracterizou-se por aparecimento de massa no hipocondrio e flanco esquerdos. A paciente nao apresentava, ao exame fisico, sinais de neurofibromatose

[Ophthalmologic differentiation of various forms of neurofibromatosis]. / Ophthalmologische Differenzierung von Neurofibromatoseformen.

Neurofibromatosis (NF) is one of the most frequent autosomal-dominant hereditary disorders. The molecular-genetic differentiation of NF 1 and NF 2 has important implications for the ophthalmologist. Among 80 patients with NF 1, Lisch nodules were diagnosed in 83% as typical criteria for the disease. In 6 patients who did not meet the NIH criteria for NF 1 and NF 2, the ophthalmological investigation showed no cataracts or Lisch nodules; thus, the ophthalmological examination can help to confirm a subtype of NF. In 8 out of 22 NF 2 patients a juvenile posterior subcapsular cataract was diagnosed. Our examination demonstrates that the diagnostic value of lens opacities in NF 2 patients--especially for early detection of the disease--must be clarified, especially with regard to the fact that there were no patients with incipient cataract and no neuroradiological criteria for the disease.

Nosological considerations of the neurofibromatoses.

We are on the threshold of evaluating the NF1 and NF2 loci with respect to variant forms of the neurofibromatoses. Genetic mapping of NF1, gene cloning and characterization of its encoded product, neurofibromin, provides a framework for the evaluation of the variant forms of NF. This may also apply to NF2 variant forms in the near future. The mapping approach in evaluating variant forms of NF should begin with the rigorous clinical assessment of familial cases whereby the establishment of genetic linkage in families with overlap syndromes might determine if either NF1, NF2, or a separate locus is involved in the phenotype. Conditions mapping to the NF1 locus could then be screened for mutations in hopes of identifying the etiologies of the variant forms of NF. Mutation identification should provide a molecular-based classification scheme for the variant forms of NF, now tentatively divided into alternative and related forms. It is expected that the nosology of the neurofibromatoses will most certainly change as more is learned of the NF1 and NF2 loci.

[Central nervous system lesions in neurofibromatosis. Clinical, MRI and histopathological correlations. A trial of classification]. / Lésions centrales dans les neurofibromatoses. Corrélations cliniques d'IRM et histopathologiques. Essai de classification.

The National Institute of Health Consensus Panel on Neurofibromatosis (NF) recently recognized 2 distinct forms of NF (NF-1 and NF-2) and stated that variant forms may exist. We selected 30 patients who fulfilled the criteria of NF-1 or whose condition was consistent with NF-2. All patients showed pathological magnetic resonance images (MRI), and in 19 cases confirmation was obtained from histopathology. We established correlations between the site and nature of the lesions on the one hand and the diagnostic criteria of NF on the other hand, there by hoping to contribute to a better knowledge and classification of neurofibromatosis. Nineteen patients had only intraparenchymatous lesions of the central nervous system (CNS) and fulfilled the criteria of NF-1; histopathological examination demonstrated pilocytic astrocytoma in 8 cases. Eleven patients showed only extra-axial lesions; 8 of them had criteria suggestive of NF-2, except for familial history. Pathological examination revealed either acoustic, pluriradicular of mixed schwannomas (7/8) or pluriradicular ganglioneuromas (1/8). Two patients had unilateral extra-axial pluriradicular cervical lesions and fulfilled the diagnostic criteria of NF-1; pathological examination revealed neurofibroma in both cases. One female patient had both intra- and extra-axial lesions that fulfilled the criteria of NF-1 and NF-2, suggesting the existence of a mixed form (NF-3).