6th ESACP Congress, Heidelberg, April 7-11, 1999

A132
ANALYSIS OF GENETIC ALTERATIONS BY COMPARATIVE GENOMIC HYBRIDIZATION IN PILOCYTIC ASTROCYRTOMAS
Szymas J 1, Petersen I 2, Wolf G 2 , Nowak S 3

1) Department of Pathology, K. Marcinkowski University of Medical Sciences, Poznan, Poland. 2) Institute of Pathology, University-Hospital Charite, Berlin, Germany, 3) Department of Neurosurgery, K. Marcinkowski University of Medical Sciences, Poznan, Poland.

Pilocytic astrocytomas are the most prevalent tumor type in children and considered being benign glioma. In this study, we used comparative genomic hybridization (CGH) to identify genetic alterations unique to this tumor type. We analyzed 18 pilocytic astroctomas by means of comparative genomic hybridization. Ten cases of pilocytic astrocytoma were located in the cerebellum and eight supratentorial. All tumors showed gains and losses of DNA by CGH, and in many cases multiple changes were observed. The most commonly observed genetic aberration, occurring in ten tumors, was deletions on chromosome 13q, suggesting that this chromosome contain loci involved in the development of pilocytic astrocytoma. Moreover, we have observed the large number of random chromosomal alterations in this tumor. The prevalent changes for cerebellar pilocytic astrocytomas were: -4q, -6q, -13q, -18q, +17p, +17q-ter, +19p, +19q whereas for supratentorial location most common changes were: -1q-ter, -2q, -13q, -19q, -20q-ter. One case of optic glioma was characterized by following changes: -6q, -14q, -17p, -19q, -21q and -22q. We concluded that although pilocytic astrocytomas are benign tumors, multiple chromosomal gain and losses were observed Specific combination of multiple chromosomal losses characterizes pilocytic astrocytomas may help to differentiate them unequivocally from other types of tumors of the central nervous system.