A case of solitary subependymal giant cell astrocytoma: two somatic hits of TSC2 in the tumor, without evidence of somatic mosaicism.

Department of Neurological Surgery, Okayama University Graduate School of Medicine and Dentistry, Japan.
Journal of Molecular Diagnostics (Impact Factor: 4.85). 10/2005; 7(4):544-9.
Source: PubMed


Subependymal giant cell astrocytoma (SEGA) is a unique brain tumor arising in tuberous sclerosis complex (TSC), an autosomal dominant inherited phacomatosis. There are several case reports of solitary SEGA without any other manifestations of TSC. Usually these cases are thought to be forme fruste of TSC due to somatic mosaicism. However, no previous reports have used molecular methodology to fully investigate mutations in TSC genes or the possibility of somatic mosaicism. Here, we report a 20-year-old woman with a brain tumor. Pathological diagnosis was consistent with SEGA, but comprehensive clinical screening found no other lesions indicative of TSC. Molecular analysis of the tumor revealed loss of heterozygosity and allelic mutation (5228G>A, R1743Q) of TSC2. To detect the small fraction of mosaic mutation in somatic cells, we developed a highly sensitive new method: triple-nested polymerase chain reaction-restriction fragment length polymorphism. The identical TSC2 missense mutation was not detected in any other tissues from the same patient, including peripheral blood, buccal mucosa, urinary sediment, nail, and hair. According to these results, this patient should be considered as having SEGA that developed from two somatic hit mutations in TSC2, rather than being a TSC2 patient with a very small fraction of somatic mosaicism.

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    ABSTRACT: Tuberous sclerosis complex (TSC) is an autosomal dominant disease characterized by the development of multiple hamartomas in many internal organs. Mutations in either one of 2 genes, TSC1 and TSC2, have been attributed to the development of TSC. More than two-thirds of TSC patients are sporadic cases, and a wide variety of mutations in the coding region of the TSC1 and TSC2 genes have been reported. Mutational analysis of TSC1 and TSC2 genes was performed in 84 Taiwanese TSC families using denaturing high-performance liquid chromatography (DHPLC) and direct sequencing. Mutations were identified in a total of 64 (76 %) cases, including 9 TSC1 mutations (7 sporadic and 2 familial cases) and 55 TSC2 mutations (47 sporadic and 8 familial cases). Thirty-one of the 64 mutations found have not been described previously. The phenotype association is consistent with findings from other large studies, showing that disease resulting from mutations to TSC1 is less severe than disease due to TSC2 mutation. This study provides a representative picture of the distribution of mutations of the TSC1 and TSC2 genes in clinically ascertained TSC cases in the Taiwanese population. Although nearly half of the mutations identified were novel, the kinds and distribution of mutation were not different in this population compared to that seen in larger European and American studies.
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    ABSTRACT: Subependymal giant cell astrocytoma (SEGA) is a benign, slowly growing tumor typically occurring in the setting of tuberous sclerosis complex (TSC). However there are several reported cases in which patients with a solitary SEGA had no other stigmata of TSC. We describe a case of SEGA in a 75-year-old woman representing the oldest patient reported to-date. The patient had a history of radical vulvectomy for malignant melanoma (MM), and died of autopsy-confirmed widespread systemic metastasis. Postmortem examination of the brain revealed a single 2.1 x 1.0 x 0.8 cm intraventricular nodule in the lateral ventricle. Histologically, it was composed of interlacing bundles of spindle-shaped tumor cells with thin delicate processes admixed with relatively large pleomorphic cells with abundant glassy eosinophilic cytoplasm, as seen in a SEGA. Immunohistochemically, GFAP, S-100 protein, and neuron specific enolase were positive, and synaptophysin labeled a few tumor cells. Also noted were rare isolated MM cells within the tumor (i.e., tumor-to-tumor metastasis). Autopsy showed no manifestations of TSC systemically or intracranially. The histopathological differential diagnosis was limited and included giant cell ependymoma and, much less likely, giant cell glioblastoma and pleomorphic xanthoastrocytoma. This case illustrates that SEGA can be found incidentally in an elderly individual with no associated symptoms and also indicates that SEGA can occur outside the setting of TSC. Tumor metastasis to an occult SEGA is extremely rare.
    Neuropathology 08/2008; 29(2):181-6. DOI:10.1111/j.1440-1789.2008.00941.x · 1.65 Impact Factor
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    ABSTRACT: Focal cortical dysplasia (FCD) is a common cause of pharmacoresistant human epilepsy. FCD has frequently been discussed as a "forme fruste" of tuberous sclerosis complex (TSC) because of the radiologic and histologic resemblance of dysplastic areas to tubers in TSC. Mutations or a germ-line predisposition in terms of increased polymorphisms in the TSC genes have been presumed to influence the pathogenesis of FCD. A detailed genotype-phenotype analysis of these patients has not been performed so far. In this study, 33 patients with FCD (among them 23 with FCD type 2 and 4 patients with multifocal FCD) were investigated (1) clinically as to dermatologic manifestations, retinal hamartoma, cardial rhabdomyoma, and renal angiomyolipoma, and (2) genetically by considering lesional brain tissue and blood using single strand conformation polymorphism (SSCP) electrophoresis and sequencing of the TSC1 and TSC2 genes. In the clinical examinations, no subtle features of TSC could be detected in this large group of patients with FCD, pointing to the fact that this is a different patient group without clinical overlap. Several sequence alterations were found in the TSC1 and TSC2 genes in both lesional brain tissue and blood of FCD patients, however, in similar frequencies to that of the normal population. Moreover, most of these sequence alterations were silent. This study shows that FCD-even multifocal FCD-is not caused by mutations in the TSC genes and seems not to be promoted by polymorphisms in the TSC genes. Therefore, FCD cannot be regarded as a "forme fruste" of TSC.
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