Combined loss of 1p and 19q is a statistically significant predictor of prolonged survival in patients with pure oligodendroglioma, independent of tumor grade. Given the lack of this association in patients with astrocytic neoplasms and the previously demonstrated chemosensitivity of oligodendrogliomas, a combined approach of histologic and genotypic assessment could potentially improve existing strategies for patient stratification and management.

PTEN mutation and EGFR amplification are important prognostic factors in patients with anaplastic astrocytoma and in older patients with glioblastoma multiforme, respectively.

Allelic alterations of chromosomes 1 and 19 are frequent events in human di use gliomas and have recently proven to be strong predictors of chemotherapeutic response and prolonged survival in oligodendrogliomas (Cairncross et al., 1998; Smith et al., submitted). Using 115 human di use gliomas, we localized regions of common allelic loss on chromosomes 1 and 19 and assessed the association of these deletion intervals with glioma histological subtypes. Further, we evaluated the capacity of multiple modalities to detect these alterations, including loss of heterozygosity (LOH),¯uorescence in situ hybridization (FISH), and comparative genomic hybridization (CGH). The correlation coe cients for detection of 1p and 19q alterations, respectively, between modalities were: 0.98 and 0.87 for LOH and FISH, 0.79 and 0.60 for LOH and CGH, and 0.79 and 0.53 for FISH and CGH. Minimal deletion regions were de®ned on 19q13.3 (D19S412-D19S596) and 1p (D1S468-D1S1612). Loss of the 1p36 region was found in 18% of astrocytomas (10/55) and in 73% (24/33) of oligodendrogliomas (P50.0001), and loss of the 19q13.3 region was found in 38% (21/55) of astrocytomas and 73% (24/33) of oligodendrogliomas (P=0.0017). Loss of both regions was found in 11% (6/55) of astrocytomas and in 64% (21/33) of oligodendrogliomas (P50.0001). All gliomas with LOH on either 1p or 19q demonstrated loss of the corresponding FISH probe, 1p36 or 19q13.3, suggesting not only locations of putative tumor suppressor genes, but also a simple assay for assessment of 1p and 19q alterations as diagnostic and prognostic markers.

The cellular origin ol the sarcomatous component of gliosarcomas is controversial. It is not clear if the sarcoma arises in transition Irom the glial cells that comprise the gliomatous component or independently arises from non-neoplastic mesenchymal cells oí the tumor stroma. Using comparative genomic hybridization (CGH) along with cytogenetic analysis, fluorescence in situ hybridization (FISH) analysis, and polymerase chain reaction (PCR) analysis of microsatellite allelic imbalance, we have evaluated the genetic alterations in the gliomatous and sarcomatous components of five gliosarcomas. The glial element was grade 4 librillary astrocytoma (glioblastoma multiforme) in all five tumors. The sarcoma elements were fibroblastic without osseous* chondroid, or angiosareomatous differentiation. Gain of chromosome 7, loss of chromosome 10, deletions of the chromosome 9 p-arm. and alterations of chromosome 3 were frequently observed, demonstrating that gliosarcomas can be genetically classified as belonging to the spectrum of glioblastomas. Furthermore, the sarcomatous and gliomatous portions of each gliosareoma investigated were similar with respect to both the presence and absence of specific genetic alterations. This observation supports the hypothesis that the sarcomatous component of a gliosareoma either arises from the same common precursor cell as the gliomatous portion, or it arises from the gliomatous portion itself.