Interphase molecular cytogenetics of Ewing's sarcoma and peripheral neuroepithelioma t(11;22) with flanking and overlapping cosmid probes.

The translocation, t(11;22)(q24;q12), recurrently observed in Ewing's sarcoma and in peripheral neuroepithelioma has been recently cloned. The analysis of a series of ES/PNE has revealed that the chromosome 22 breakpoints are clustered in a small region of 7 kb, called EWSR1, and that those on chromosome 11 are spread over a larger region of 40-50 kb, called EWSR2. Cosmids from loci flanking or overlapping these two regions have been obtained. We demonstrate here that fluorescence in situ hybridization (FISH) with these cosmids allows the localization of the two breakpoints with a 10-kb resolution and leads to a rapid and reliable ES/PNE diagnosis.