Peterson JF, Pearce KE, Meyer RG, et al. - Researchers sought to examine their 5-year experience with clinical FISH testing for TP63 rearrangements utilizing both TP63 break-apart (BAP) and TBL1XR1/TP63 dual-fusion (D-FISH) probes to estimate the frequency of TP63 rearrangements and the distribution of TBL1XR1 vs. alternate partner loci and to evaluate whether both probe sets are necessary in all cases undergoing FISH testing. In a retrospective review of the Mayo Clinic cytogenetic database, they examine a sum of 470 individuals by FISH testing for TP63 rearrangements in formalin-fixed paraffin-embedded (FFPE) tissue using both BAP and D-FISH probes. Among cases referred to a large reference laboratory, the frequency of positive results for TP63 FISH testing was 5.3%. Nearly half of TP63 rearrangements have a TBL1XR1 partner. The data showed that TP63 BAP FISH testing is satisfactory for up-front testing of FFPE tissue samples. They suggested reflex TBL1XR1/TP63 D-FISH testing in positive and equivocal cases, because of the genomic proximity of the TP63 and TBL1XR1 loci.