The family/class of the large B-cell lymphomas (LBCL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) features only a few major changes as compared to the 4th edition. In most entities, there are only subtle changes, many of them only representing some minor modifications in diagnostic terms. Major changes have been made in the diffuse large B-cell lymphomas (DLBCL)/high-grade B-cell lymphomas (HGBL) associated with MYC and BCL2 and/or BCL6 rearrangements. This category now consists of MYC and BCL2 rearranged cases exclusively, while the MYC/BCL6 double hit lymphomas now constitute genetic subtypes of DLBCL, not otherwise specified (NOS) or of HGBL, NOS. Other major changes are the conceptual merger of lymphomas arising in immune-privileged sites and the description of LBCL arising in the setting of immune dysregulation/deficiency. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of the different entities are provided.

The conceptual description of Follicular lymphoma (FL) in the 5th edition of the World Health Organization (WHO) classification of haematolymphoid tumors (WHO-HAEM5) has undergone significant revision. The vast majority of FL (85%) with a follicular growth pattern are composed of centrocytes and centroblasts, harbor the t(14;18)(q32;q21) translocation and are now termed classic FL (cFL). They are set apart from three related subtypes, FL with predominantly follicular growth pattern, FL with unusual cytological features (uFL) and follicular large B-cell lymphoma (FLBCL). In contrast to the revised 4th edition of the WHO classification of haematolymphoid tumors (WHO-HAEM4R), grading of cFL is no longer mandatory. FL with a predominantly diffuse growth pattern had been previously recognized in WHO-HAEM4R. It frequently occurs as a large tumor in the inguinal region and is associated with CD23 expression. An absence of the IGH::BCL2 fusion and frequent STAT6 mutations along with 1p36 deletion or TNFRSF14 mutation is typical. The newly introduced subtype of uFL includes two subsets that significantly diverge from cFL: one with “blastoid” and one with “large centrocyte” variant cytological features. uFL more frequently displays variant immunophenotypic and genotypic features. FLBCL is largely identical to WHO-HAEM4R FL grade 3B and renaming was done for reasons of consistency throughout the classification. In-situ follicular B-cell neoplasm, pediatric-type FL, duodenal-type FL and primary cutaneous follicle center lymphoma are categorized as discrete entities. In addition, novel findings concerning underlying biological mechanisms in the pathogenesis of early and systemic follicular lymphoma will be presented.

Treatment response of follicular lymphomas (FL) is highly variable. We, therefore, investigated the role of FL cancer-associated fibroblasts (CAFs) on tumor cell viability, in particular in response to treatment with cytotoxic drugs. Stromal cells outgrown from FL patients were characterized and pure CAF populations were co-cultivated with FL cells. To analyze fibroblast-mediated effects, cells in co-culture were treated with ABT-737 and Bortezomib. The adherent cell population was positive for all fibroblastic markers tested and showed increased mRNA-expression of the activation marker FAP. No effect on FL cell viability was noted when co-cultivating them with CAFs. However, stromal cells protected tumor cells from apoptosis in response to cytotoxic treatment. This might be explained by mRNA-induction of ABCC1 and ABCG2 and up-regulation of BCL2L1 in FL cells. Our finding of protective mechanisms mediated by CAFs is of pivotal impact for further studies of cytotoxic agents in FL.

The impact of single-nucleotide polymorphisms (SNPs) on tumour susceptibility and pathogenesis has gained enormous attention. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)-based genotyping facilitates the analysis of short DNA amplicons and is, therefore, a promising tool for the investigation of formalin-fixed paraffin-embedded (FFPE) tissue samples, particularly in targeted genotyping analysis. To examine the applicability of genotyping FFPE DNA with MALDI-TOF MS in multiplex reactions, we investigated five DNA samples extracted from FFPE tumour specimens from follicular lymphoma patients using different extraction methods (phenol-chloroform, commercial kit). Thirty-one SNPs from 25 genes, integrated in different-sized multiplex assays (7-plex, 10-plex, 14-plex, 24-plex), were analyzed. To investigate the reliability of genotyping tumour-derived DNA extracted from FFPE tissue, we examined 64 FFPE tumour specimens in comparison with matched germline DNA samples. Call rates of 99.6 (274/275) and 93.5% (257/275) were observed for the DNA extracted with the phenol-chloroform approach or the commercial extraction kit, respectively. Increasing the number of SNPs per assay resulted in reduced genotyping call rates and genotyping quality, especially in the DNA samples isolated with the commercial extraction kit. When comparing the genotypes of DNA derived from germline and tumour (FFPE) specimens, a perfect concordance rate of 100% was detected. Our data delineate that MALDI-TOF-based genotyping of FFPE DNA is reliable and reproducible even in multiplex reactions, enabling the retrospective investigation of FFPE study cohorts in future experiments.

Introduction: Owing to tremendous advances in the understanding of mechanisms involved in the pathogenesis of malignant tumors an emerging field of novel targeted drugs has evolved within the last decade. This is of particular interest also for malignant lymphomas, constituting a heterogeneous tumor category with substantial variation in clinical outcome, ranging from indolent forms that do not require treatment over years to aggressive cases for which an immediate treatment is mandatory. The elucidation of different molecular strategies adopted by malignant cells has led to a profound profiling of tumor-specific features and consequently resulted in the development of new targeted therapies. Areas covered: A review of currently tested tailored approaches, in particular in B-cell lymphomas (B-NHL), ranging from monoclonal antibodies to inhibition of intrinsic and extrinsic effector molecules. These approaches are currently tested in several subtypes of B-NHL both in preclinical studies and in clinical trials and are summarized within this review. Expert commentary: Considering how quickly basic scientific discoveries could meanwhile be transferred to clinical trials and approvals, future perspectives for novel tailored therapeutic strategies are promising.