Evolution of tumor chromosome abnormalities after therapy in a pediatric astrocytoma.

Chromosome studies originally performed on a patient with an untreated pontine astrocytoma showed a trisomy for 1q as the sole chromosome aberration. After the patient received radiation and chemotherapy, subsequent study indicated the presence of the original trisomy for 1q, as well as trisomy for chromosomes 2, 3q, and 17, in a tumor that now, histologically, is glioblastoma multiforme. In addition to the numerical aberrations, chromosome rearrangements were observed, involving translocation breakpoints that have been reported as "hot spots" associated with the clastogenetic effect of ionizing radiation.