The EWSR1 Breakapart probe contains a red 392kb probe and a green 631kb probe, which are positioned on each side of the EWSR1 gene.
Ewing's sarcoma (EWS) is the second most frequent primary bone cancer in patients under 20 years of age1. It is mainly characterised by a translocation between the two genes - EWSR1 (Ewing's Sarcoma Region 1) and FLI1 (Friend Leukaemia virus Integration 1) - in the t(11;22)(q24;q12) translocation, found in 83% of such tumours2. 10% of the remaining cases have a variant translocation involving EWSR1 and ERG, t(21;22)(q22;q12), and less than 1% carry one of the 7p22 (ETV1), 17q12 (E1AF) or 2q36 (FEV) translocations with EWSR13.
EWSR1 is also involved in translocations in desmoplasmic small round cell tumours, a subset of angiomatoid fibrous histocytomas, and possibly in myxoid liposarcoma4,5.
The EWSR1 breakapart probe can also be used to distinguish rare soft tissue sarcoma, a clear cell sarcoma, from malignant melanoma, a distinction that is difficult to make via either histology or immunohistology. The EWS-ATF1 (Activating Transcription Factor 1) translocation, t(12;22) (q13;q12), has been identified in 70-90% of clear cell sarcoma yet has not been observed in malignant melanoma6. This translocation can be detected using the EWSR1 breakapart probe.
FISH has been shown to be a more sensitive and reliable method than RT-PCR for the diagnosis of EWS in solid tissues7.
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