Genetic heterogeneity in follicular lymphoma

: The genetic underpinnings of follicular lymphoma (FL) are now better understood through sequencing efforts of the last decade. Epigenetic deregulation, particularly through mutations in chromatin-modifying enzymes, is recognised as a pivotal hallmark that occurs alongside the t(14;18) chromosomal translocation, together with mutations in genes that affect a number of secondary biological pathways including mTORC1, JAK-STAT, NF-kB signalling and immune evasion. In recent years, the functional relevance of these genetic aberrations has been independently deciphered. The protracted nature of FL has provided an excellent model to chart the heterogeneity and evolution of the genetic features of the lymphomas both temporally and spatially. These studies have pointed to the early and late genetic drivers of the disease and the existence of a putative reservoir population that is difficult to eradicate with conventional treatment and most likely contributes to the relapsing-remitting nature of FL. Additionally, these sequencing studies have identified similarities and distinct differences in the genetic profiles of FL compared to related histological entities. In this review, we aim to summarise the current state of our understanding of the genetic landscape and heterogeneity, its contribution to the spectrum of clinical phenotypes in FL and related entities and finally, the ongoing efforts to utilise biology to provide lines of sight to the clinic.