IDH2 and angioimmunoblastic T-cell lymphoma: Recently, a multistep lymphomagenesis model was proposed, in which the premalignant hematopoietic progenitor cells harboring early mutations in epigenetic regulators TET2, DNMT3A are predisposed to the development of blood cancer, and the second-hit mutations such as RHOA (G17V) and IDH2 (R172) in a subclone of TFH cells eventually leads to AITL [39–41].