IGLL5 and hairy cell leukemia: FGR is not only connected to NFIB, but FGR also shares a protein–protein interaction with IGLL5 and a gene–gene interaction with FCRL1. FCRL1 expressed in a majority of chronic lymphocytic leukemia, follicular lymphoma, hairy cell leukemia, and mantle cell lymphoma38 and might play an important role in the onset of these malignancies.