High frequency of IDH-1 mutation links glioneuronal tumors with neuropil-like islands to diffuse astrocytomas

Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY, 10065, USA, .
Acta Neuropathologica (Impact Factor: 10.76). 07/2011; 122(3):367-9. DOI: 10.1007/s00401-011-0855-6
Source: PubMed
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    ABSTRACT: Glioneuronal tumor with neuropil-like islands (GTNI) is featured by "neuropil-like islands (NIs)" within dominating astroglial components. Isocitrate dehydrogenase (IDH) mutations, particularly IDH1 R132H (G395A), are found in WHO Grade II and III diffuse gliomas as well as secondary, but not primary, glioblastomas. We reviewed 5 cases of GTNI, and assessed histology and immunohistochemistry with various antibodies, including those for IDH1 R132H, as well as direct DNA sequencing for IDH1 G395A. NIs were variable in morphology, and constantly synaptophysin-positive and glial fibrillary acidic protein-negative. The glioma components were primary glioblastoma in 2 cases, anaplastic astrocytoma in 1 and anaplastic oligoastrocytoma in 2. The IDH1 R132H was expressed in the 2 cases with oligoastrocytoma: In 1, NIs and the astrocytoma-like area as well as the oligodendroglioma-like area were positive. In the other, only the oligodendrogliomalike area was positive. The mutation analysis performed on the latter case with DNA separately sampled from the oligodendroglioma- like area and the astrocytoma-like area detected IDH1 G395A in both areas. We have shown diverse pathologic aspects of GTNI. Also, we have shown that the expression of IDH1 R132H in GTNI is largely concordant with that in diffuse gliomas, and that it can be dependent on each histologic component although the mutant IDH1 gene is ubiquitously present within the tumor.
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    ABSTRACT: The term long-term epilepsy associated tumor (LEAT) encompasses lesions identified in patients investigated for long histories (often 2 years or more) of drug-resistant epilepsy. They are generally slowly growing, low grade, cortically based tumors, more often arising in younger age groups and in many cases exhibit neuronal in addition to glial differentiation. Gangliogliomas and dysembryoplastic neuroepithelial tumors predominate in this group. LEATs are further united by cyto-architectural changes that may be present in the adjacent cortex which have some similarities to developmental focal cortical dysplasias (FCD); these are now grouped as FCD type IIIb in the updated International League Against Epilepsy (ILAE) classification. In the majority of cases, surgical treatments are beneficial from both perspectives of managing the seizures and the tumor. However, in a minority, seizures may recur, tumors may show regrowth or recurrence, and rarely undergo anaplastic progression. Predicting and identifying tumors likely to behave less favorably are key objectives of the neuropathologist. With immunohistochemistry and modern molecular pathology, it is becoming increasingly possible to refine diagnostic groups. Despite this, some LEATs remain difficult to classify, particularly tumors with "non-specific" or diffuse growth patterns. Modification of LEAT classification is inevitable with the goal of unifying terminological criteria applied between centers for accurate clinico-pathological-molecular correlative data to emerge. Finally, establishing the epileptogenic components of LEAT, either within the lesion or perilesional cortex, will elucidate the cellular mechanisms of epileptogenesis, which in turn will guide optimal surgical management of these lesions.
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