[1685] Novel Translocation t(9;17)(q32;q24) in a Glioneuronal Tumor

RD McComb, LA Bruch, CA Reyes, MJ Puccioni, JA Bridge. University of Nebraska Medical Center, Omaha, NE; University of Iowa, Iowa City, IA; Children's National Medical Center, Washington, DC; Midwest Neurosurgery, Omaha, NE

Background: Glioneuronal tumors (GNT) with mixed neurocytic/ganglioid and glial components are rare and difficult to subclassify. One recently recognized variant, papillary GNT, is identified by the presence of a specific pseudopapillary architecture. Genetic data on such tumors are limited; gain of structurally aberrant chromosome 7 material was identified in an isolated case of papillary GNT.
Design: A seven-year-old boy underwent gross total resection of a large parieto-occipital cystic tumor that showed irregular contrast-enhancement. In addition to histologic and immunohistochemical evaluation, a representative portion of the tumor was examined by conventional cytogenetic analysis using standard procedures. The karyotypes were described according to the International System for Human Cytogenetic Nomenclature (ISCN 2009).
Results: Pathologic evaluation revealed a mixed glioneuronal tumor with a prominent synaptophysin-positive neurocytic/ganglioid cell component intimately mixed with a GFAP-positive glial element. Much of the tumor exhibited sheet-like growth with a delicate microvasculature. Focal areas showed a pseudopapillary architecture in which hyalinized blood vessels were ensheathed by a layer of tumor cells. GFAP-positive cells were located in the diffuse and interpapillary areas as well as perivascular regions. Mitoses were not identified, and the Ki67 immunolabeling index was low. Cytogenetic analysis revealed a diploid clone characterized by the following reciprocal translocation as the sole anomaly: t(9;17)(q32;q24). Six cells with a normal male 46,XY complement were also observed.
Conclusions: This tumor showed features of a papillary GNT with a prominent glial component. A novel 9;17 translocation was identified as the sole karyotypic abnormality, suggesting it could play an important role in the pathogenesis of this tumor and potentially serve as a useful diagnostic marker if it proves to be recurrent. In addition, these findings focus attention on specific regions of chromosomes 9 and 17 that may contain genes central to the glioneuronal neoplastic process.
Category: Neuropathology

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 232, Tuesday Afternoon


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