HOOK3 and cancer: HOOK3 immunostaining was seen in 74.3% and 76.1% of cancers with TMPRSS2:ERG fusion detected by IHC and FISH, but found in only 38.2% of cancers without ERG staining and 44.1% of cancers without ERG rearrangements detected by FISH (p<0.0001 each, Fig 2).