[1695] Intratumoral Heterogeneity of Chromosomal 1p/19q Status among Glial Neoplasms: Correlation with Outcome

N Schiavo, M Brunelli, G Martignoni, F Menestrina, F Lupidi, C Ghimenton. University of Verona, Verona, Italy; Ospedale Civile Maggiore, Verona, Italy

Background: Loss of 1p/19q is considered an important diagnostic and favourable prognostic parameter in oligodendrogliomas. Fluorescent in situ hybridization (FISH) is one of the most used technique for investigation of 1p/19q status in paraffin-embedded tissues. Heterogeneous intratumoral pattern of fluorescent signal scoring have been sometimes reported. We sought to assess different pattern and heterogeneity of 1p and 19q status among glial neoplasms.
Design: To test 1p/19q regions FISH analysis was used in a series of 49 glial neoplasms (26 oligodendrogliomas, 16 astrocytomas, 7 oligoastrocytomas) and 5 gliotic brain tissue as controls. For each case at least 200 nuclei were scored for fluorescent signals and different cut-offs were calculated to distinguish different pattern. We reported survivals on 32 patients among a period of 8 years (range: 3-8 years).
Results: 69% of oligodendrogliomas showed both chromosome 1p/19q deletions, 12% were not deleted, 12% presented gains of 1p signals, 8% displayed a polysomic pattern. Among cases with 1p/19q deletions, 12 cases (46%) showed heterogeneous population of nuclei characterized by gains and loss at 1p associated with deletion of 19q. Astrocytomas showed deletions of chromosomes 1p/19q in 6% of cases, polysomy in 81% whereas 7% were not deleted. Three oligoastrocytomas presented deletion, three with polysomy and one with gains of 1p Survival rate at the 8th year of observation was better in oligodendrogliomas (60%) than in astrocytomas (20%). Survival analysis revealed a similar trend between oligodendrogliomas with 1p/19q deleted pattern and tumours having heterogeneous pattern (about 70% of patient of both groups were alive at 8th year from diagnosis).
Conclusions: 1p/19q loss is more frequent in oligodendroglioma than in astrocytoma, the latter characterized by a polysomic pattern. Oligodendrogliomas present subgroups, such as isolated gains or heterogeneous gains and loss of 1p associated to loss of 19q, that could be referred as having a deleted pattern with a similar time of overall survival. 1p/19q status in oligoastrocytomas probably reflects the more oligodendrocytic or astrocytic nature of the neoplasm.
Category: Neuropathology

Tuesday, March 23, 2010 1:30 PM

Platform Session: Section G, Tuesday Afternoon


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