Abstract Diffuse large B cell lymphoma (DLBCL), the most common form of human lymphoma, is a heterogeneous neoplasm comprising multiple genetic, phenotypic and clinical subtypes, approximately 50% of which are incurable. These tumors may arise de novo or from the transformation of more indolent lymphomas, as observed in 30-40% of follicular lymphoma (FL) cases. Over the past decade, the introduction of next-generation sequencing technologies combined with genome-wide copy number analysis has allowed to comprehensively define the genomic landscape of this disease, leading to the identification of multiple genes and signaling pathways that are dysregulated by genetic lesions and represent potential targets for diagnosis and therapy. In addition to perturbations in the transcriptional control of apoptosis, differentiation and DNA damage responses or NF-κB activation, these efforts revealed the frequent targeting of genes implicated in chromatin remodeling and immune recognition/surveillance. In particular, one of the most commonly disrupted programs in both de novo DLBCL, FL and transformed FL (tFL) comprises genes encoding histone/chromatin modifying enzymes, including methyltransferases (MLL2, EZH2) and acetyltransferases (CREBBP, EP300), which may play a central role during malignant transformation. Interestingly, sequential analysis of tumor samples during transformation of FL to tFL indicates that inactivating mutations of CREBBP and MLL2 are acquired early in the evolutionary history of a common mutated ancestral clone. The disruption of these genes by genetic alterations may thus contribute to malignant transformation by shaping the epigenetic landscape of the cancer cell as well as by perturbing specific biological programs, in part through the altered balance between acetylation-mediated activation of the p53 tumor suppressor and inactivation of the BCL6 proto-oncogene. This talk will cover recent advances in understanding the genetic basis of DLBCL, as revealed by in vitro and in vivo studies. Citation Format: Laura Pasqualucci. The genetic basis of diffuse large B cell lymphoma. abstract. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr IA39.