Tumor location and growth pattern correlate with genetic signature in oligodendroglial neoplasms

Molecular genetic subsets of anaplastic oligodendroglioma behave in biologi cally distinct ways, in both their rates of growth and their responses to s tandard therapies. In a series of 64 cases, we evaluated whether allelic lo ss of chromosomal arms lp and 19q, an early molecular event in the genesis of chemosensitive oligodendrogliomas, is related to tumor location and exte nt of tumor spread in the brain. We observed that tumor genotype was closel y associated with tumor location (P < 0.001). Anaplastic oligo dendroglioma s located in the frontal, parietal, and occipital lobes were significantly more likely to harbor allelic loss of chromosomal arms lp and 19q than hist ologically indistinguishable tumors arising in the temporal lobe, insula, a nd diencephalon (P < 0.001). In addition, loss of heterozygosity for lp and 19q was significantly associated with a bilateral pattern of growth (P = 0 .037); all seven bilaterally distributed anaplastic oligodendrogliomas had lp and 19q allelic loss. We conclude, therefore, that molecular subtypes of oligodendrogliomas may arise preferentially in certain lobes of the brain and have differential patterns of growth, with tumors having allelic loss o f chromosomes lp and 19q occurring most frequently in the frontal lobes and having a tendency for widespread growth across the midline. These findings encourage inquiries into the biological basis of such marked differences a nd already have implications for the current management of these neoplasms.