PRDM9 and neoplasm: Epigenetics is defined as heritable changes in gene expression mediated mostly by DNA methylation and histone tail modifications without changes in DNA sequence.1 Epigenetic abnormalities in cancer lead to reprogramming of gene expression resembling embryonic stem cells, loss of tumor suppressors, or reactivation of oncofetal genes.2, 3 For example, enhanced histone 3 lysine 27 trimethylation (H3K27me3), mediated by a complex of proteins, including the histone methyltransferase EZH2, causes the silencing of tumor-suppressor genes.4, 5