Molecular genetic analysis of archival gliomas using diagnostic smears

Investigation of the clinical significance of genetic alterations in glioma s requires molecular genetic analysis using samples from retrospective or p rospective clinical studies. However, diagnostic tissue is often severely l imited and because of fixation, paraffin-embedded tissues (PET) contain deg raded DNA. Intra-operative cytological preparations (smears) archived after diagnosis may represent an additional source of clinical material for gene tic analysis. In this study, tissue samples were obtained by precision micr odissection of archived diagnostic smears from 20 cases (1961-1999). All sa mples produced polymerase chain reaction (PCR) products for the beta globin gene, but the most recent samples amplified best and gave longer amplimers . For six cases, direct comparison was made between samples microdissected from smears and the corresponding PET. Samples from smears showed improved PCR performance and similar alleles on microsatellite marker analysis. One case, with smears of uninvolved cortex and tumour tissue available for micr odissection, showed allelic imbalance at 10q23 on the basis of the smear re sults alone. PCR products from smears were shown to be suitable for direct sequence analysis (p53 gene). A PTEN mutation, found previously in an anapl astic astrocytoma by analysis of PET, was detected in the corresponding dia gnostic smear. The results of this study indicate that tissue samples micro dissected from diagnostic intra-operative cytological preparations may be s uitable for molecular genetic analysis of gliomas.