BCR-ABL1-like ALL (Ph-like ALL) is associated with a poor prognosis (5-year DFS of 60%) and is less common in pediatric B-cell ALL, at approximately 3%; however, it is the most common subtype in adult ALL, at approximately 25%.The incidence of Ph-like ALL is positively correlated with advancing age.Kinase activation is seen in 90% of Ph-like ALL Abnormalities such as ABL1, EPOR, JAK2, PDGFRB, EBF1, FLT2, IL7R, and SH2B3 are seen in 90% of Ph-like ALL and may be amenable to ABL1 TKI therapy. CRLF2 gene rearrangements can occur in approximately 30% of pediatric Ph-like ALL patients, of which approximately 90% are fusions with P2RY8 and 10% are fusions with IGH, and are associated with poor prognosis.

This probe can be used in conjunction with the F.01235-01CRLF2 (Xp22 Yp11) gene breakage probe (fluorescence in situ hybridization) for further differentiation of its partner genes. In particular, the type of P2RY8 fusion with CRLF2 is rather special, being a fusion with deletion, which is manifested as an atypical positive signal of 1 green and 1 yellow of the CRLF2 breakthrough probe. Therefore, when this type of signal is encountered using the CRLF2 breakage probe, it can be determined that its partner gene is P2RY8.