PRIMITIVE NEUROECTODERMAL TUMORS OF THE CEREBRUM AND CEREBELLUM - ABSENCE OF T(11-22) TRANSLOCATION BY RT-PCR ANALYSIS

Cytogenetic analysis of peripheral primitive neuroectodermal tumors (P NETs) has demonstrated a consistent primary chromosomal change charact erized by a reciprocal translocation t(11; 22)(q24:q12). In the centra l nervous system PNETs, most frequent of which are the cerebellar medu lloblastomas, the most prevalent chromosomal abnormalities include del etions and unbalanced translocations. The recent cloning of the t(11;2 2) breakpoint has revealed the fusion of the human FLI-1 gene on chrom osome 11q24 with a gene EWS on chromosome 22q12 and permitted detectio n of fusion transcripts, Molecular genetic analysis for the presence o f EWS/FLI-1 fusion transcripts by the reverse transcriptase-polymerase chain reaction has recently been applied to peripheral PNETs. In the present study, we analyzed eight central PNETs by reverse transcriptas e-polymerase chain reaction for EWS/FLI-1 fusion transcripts. The tumo rs included six PNETs of the cerebellum, one supratentorial PNET of th e frontal lobe and one PNET of the pineal region. Polymerase chain rea ction analysis in all eight cases failed to reveal a t(11;22) transloc ation indicating that this is not a cytogenetic abnormality of the cen tral PNETs. Reverse transcriptase-polymerase chain reaction analysis o f EWS/FLI-1 fusion transcripts provides a novel adjunctive tool in the differentiation of central versus peripheral PNET.