Identification of subgroups of high-grade oligodendroglial tumors by comparative genomic hybridization

In contrast to astrocytic tumors, approximately two thirds of anaplastic ol igodendrogliomas are reported to be chemosensitive. Relatively little is kn own about the genetic aberrations in oligodendroglial tumors (OTs). In orde r to elucidate oligodendroglial oncogenesis and to find specific genetic ab errations that may have prognostic and therapeutic implications, we perform ed comparative genomic hybridization (CGH) to detect chromosomal copy numbe r changes in 17 low-grade OTs (LG-OTs) and 12 high-grade OTs (HG-OTs) lacki ng a prominent astrocytic component. Loss of chromosome 1p (798) and 19q (7 6%) were most frequently detected by CGH, all LG-OTs and 50% of the HG-OTs contained -1p (including 1p36-32), -19q (including 19q13.3), or both, and t he rest of the HG-OTs showed +7, -10, or both. Since losses of 1p36-32 and 19q13.3 were mutually exclusive with +7 or -10, the HG-OTs could be divided in -1p/-19q and +7/-10 tumors. While the -1p/-19q tumors can be considered as pure anaplastic oligodendrogliomas, the +7/-10 tumors may rather be gli oblastomas with prominent oligodendroglial differentiation. We conclude tha t CGH is a powerful tool to assist in the identification of 2 major subgrou ps of HG-OTs with prognostic and possibly therapeutic relevance.