Box 1 • HG/LBCL-11q is defined by chromosome 11q-gains and telomeric loss and can occur in the setting of immunodeficiency including post-transplant and HIV+ patients but also in patients with ataxia-telangiectasia. • FISH analysis is recommended for the diagnosis of HG/LBCL-11q. • LMO2 is a useful diagnostic marker for HG/LBCL-11q but expressed only in 50% of the cases. Burkitt lymphoma is LMO2 negative. • LBCL-IRF4 is mainly a disease of children and young adults but it also occurs in adults and elderly patients. • LBCL-IRF4 in children and young adults affects predominantly the Waldeyer’s ring and presents in clinical stages I/II; in contrast, in adults, it is more often a nodal disease and presents in advanced clinical stages (III/IV). • LBCL-IRF4 is an indolent lymphoma with excellent prognosis. • Morphologically, LBCL-IRF4 can be purely follicular, follicular/diffuse, or diffuse and often shows aberrant expression of CD10, BCL6, and MUM1. CD5 expression is not rare, especially in children. • In adults, IRF4 rearrangements can be observed in a variety of aggressive B-cell lymphomas in association with other chromosomal alterations. These cases should not be diagnosed as LBCL-IRF4. • Other novel molecular groups are discussed.