EZH2 and aneurysmal bone cyst: Gene expression profiling studies have contributed to unravel the complex biological and clinical heterogeneity of this disease, leading to the definition of a germinal center (GC) B-like DLBCL (GCB) subgroup and an activated B-like DLBCL (ABC subgroup), characterized by gene expression signatures such as constitutive activation of nuclear factor kB (NFkB) in ABC subgroup [4] and somatic mutations of polycomb repressor-2 complex gene EZH2 in GCB subgroup [5].