Subtyping of oligo-astrocytic tumours by comparative genomic hybridization

Oligo-astrocytic tumours (OAs) histologically show both oligodendroglial an d astrocytic differentiation. Unequivocal criteria for delineation of OAs f rom pure oligodendroglial (Os) and astrocytic (As) tumours and for grading of OAs are lacking, Molecular genetic analysis may allow for a better chara cterization of OAs and thereby guide prognostic and therapeutic decisions. Comparative genomic hybridization (CGH) was performed on 39 gliomas with va riable phenotypic expression of histological features characteristic of bot h astrocytic and oligodendroglial differentiation. The results show that OA s are genetically more heterogeneous than Os. In addition to the '- 1p/ - 1 9q' and '+ 7/ - 10' subtypes that have been previously recognized, two addi tional generic subtypes, 'intermediate' and 'other', were identified in the present study. 'Intermediate' OAs likely represent progression from '-1p/- 19q' tumours. The 'other' subtype appears to represent an additional, heret ofore unrecognized, genetic pathway (s). Application of rigorously 'strict' histopathological criteria, as opposed to 'relaxed' criteria, for the sele ction of oligo-astrocytic rumours resulted in a higher percentage of '-1p/- 19q' rumours, but some '- 1p/-19q' tumours might be missed. The results sug gest that molecular genetic analysis is a useful and valid additional tool for the classification of gliomas, particularly for the significant subset of rumours in which subjective histopathological criteria are insufficient for an unequivocal distinction between Os, As, and mixed OAs. Copyright (C) 2001 John Wiley & Sons, Ltd.