PRDM9 and cancer: The recent discovery of recurrent mutations in another histone methyltransferase, KMT2D, in IM highlights the importance of epigenetics in the tumorigenesis of this uncommon tumor.2 From studies of cancers in other parts of the body, therapies that target tumor addiction to epigenetic dysregulation, such as recurrent EZH2 overexpression or gain of function mutations, have emerged as one of the most promising strategies against cancer.