Comparative genomic hybridization indicating two distinct subgroups of pilocytic astrocytomas

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Abstract
Object: The authors investigated the spectrum of chromosomal imbalances of pilocytic astrocytoma by using comparative genomic hybridization (CGH). Methods: Tumor DNA was extracted from surgically obtained samples of 18 pilocytic astrocytomas that were examined for the presence of neoplastic tissue on frozen sections. Comparative genomic hybridization was performed using standard procedures, and digital image analysis was conducted using out by custom-made software. The chromosomal alterations were determined by a statistical procedure in which Student's t-test (99% confidence interval) was used. Details on CGH analysis and individual ratio profiles are available at http://amba.charite.de/cgh/. Conclusions: The results suggests the presence of two distinct genetic subgroups of pilocytic astrocytoma, with imbalances of chromosome 19 being the major change for differentiation. In the first group (10 samples), deletions on chromosome 19 were shown as well as multiple gains mainly on chromosomes 5 and 6q but also on chromosomes 4, 7, 8, 10, and 11. The second group (eight samples) was characterized by overrepresentation on chromosomes 19p and 22q, which were associated with deletions on 4q, 5q, 6q, 9p, 13q, and 18q. To understand the diverse biological and clinical behavior exhibited by this tumor type, it is important that pilocytic astrocytomas be classified into distinct subgroups according to their genetic makeup.