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We herein present an overview of the upcoming 5 th edition of the World Health Organization Classification of Haematolymphoid Tumours focussing on lymphoid neoplasms. Myeloid and histiocytic neoplasms will be presented in a separate accompanying article. Besides listing the entities of the classification, we highlight and explain changes from the revised 4 th edition. These include reorganization of entities by a hierarchical system as is adopted throughout the 5 th edition of the WHO classification of tumours of all organ systems, modification of nomenclature for some entities, revision of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities, as well as inclusion of tumour-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms., (© 2022. The Author(s).)

To determine whether the expression levels of Bcl-2 family apoptotic regulators are correlated with the histopathological heterogeneity of B cell non-Hodgkin's lymphomas (NHL), we quantified their expression in malignant B cell populations isolated from 33 biopsy samples, including small lymphocytic lymphoma (SLL, n = 9), mantle cell lymphoma (MCL, n = 8), follicular lymphoma (FL, n = 8), and diffuse large cell lymphoma (DLCL, n = 8). Normal B cells purified from reactive lymph nodes and tonsil (n = 3) were used as controls. Cell lysates were analyzed by Western blotting, and signals quantified by densitometry. Expression of Bcl-2 and its homologues, Bcl-xL, Bcl-xS, Bax, Bad, Bak and Bag-1, was detected in all NHL cases, with wide variations between histological subtypes and within each subtype. Statistically significant differences were: (1) a higher level of Bad expression in DLCL compared to FL and MCL; (2) a lower level of Bak expression in FL compared to DLCL, SLL and MCL; and (3) a higher Bag-1 expression level in FL compared to SLL. When compared to NHL cells, normal B cells showed a higher level of Bax expression, and a lower level of Bcl-xL expression. Thus, quantitative analysis shows ubiquitous expression of Bcl-2 family proteins in normal and neoplastic B cells; the variations in expression levels may contribute to both the B-NHL clinicopathological diversity and the different apoptotic sensitivities of normal B cells vs B-NHL cells.

We previously reported feasibility and efficacy of a monocentric pilot study of intensive sequential chemotherapy (ISC) in poor-risk aggressive non-Hodgkin's lymphoma (NHL) in patients < 60 years. To validate these results on a large cohort of patients, we designed a new and oligocentric study. After a COP (cyclophosphamide (Cy), vincristine (Vcr), prednisone (Pred) debulking, patients received four courses of high-dose CHOP (Cy, doxorubicin (Doxo), Ver, Pred), with the addition of etoposide and cisplatin during the two last courses. G-CSF was delivered after each cycle, and peripheral blood stem cells (PBSC) were used to support the two last cycles. Total duration of chemotherapy was 13 weeks, with a planned dose-intensity (DI) of 1420 mg/m2/week and 23 mg/m2/week for Cy and Doxo, respectively. Radiotherapy (involved fields) was then delivered for patients with node size > or = 5 cm at diagnosis. Forty-two patients were enrolled in this study; 36 completed the treatment and received 75% or more of the planned DI for both Cy and Doxo. Median duration of grade 4 neutropenia was 14 days (range, 2 to 28) for the regimen as a whole, and median duration of rehospitalization for febrile neutropenia was 18 days (range, 4 to 41). Overall response rate was 83%, with 29 patients (69%) in complete response (CR). Six patients failed to respond and one died of toxicity. With a median follow-up of 22.5 months (range, 10 to 42), the 3-year event-free survival (EFS) is 55% (95% CI, 39-71), while disease-free survival (DFS) is 79% (95% CI, 63-95). Ambulatory ISC is accessible and feasible in an oligocentric study. PBSC allow repeated delivery of high-dose chemotherapy cycles, and result in encouraging CR, EFS, and DFS rates for poor-risk aggressive NHL's patients.

Fas ligand (FasL) is capable of inducing apoptosis of lymphoid cells by cross-linking with its natural receptor, Fas. We aimed to investigate the possible role of the Fas/FasL-mediated apoptosis in the development of human lymphomas. FasL mRNA was detected by reverse transcriptase-polymerase chain reaction in 38 out of 63 lymphoma biopsy specimens representative of various subtypes of non-Hodgkin's lymphoma (NHL) and Hodgkin's disease. FasL was co-expressed with Fas mRNA in most cases. Flow cytometry (FACS) analysis showed a bright FasL staining in 31% to up to 75% of the total cell population from 14 out of 16 samples; the presence of the FasL protein was confirmed by Western blotting. Dual-color FACS analysis showed that FasL was expressed by T cells in B-NHLs and T-NHLs. A significant percentage of B cells in various B-NHLs also stained positively for FasL. Freshly separated neoplastic B cells from three FasL+ and one FasL- B-NHLs displayed a relative resistance to Fas-mediated apoptosis, when compared to reactive T cells isolated from the same tissue samples. In contrast, the sensitivity to Fas-mediated killing of the T cells isolated from two FasL+ T-NHLs was not uniform. These data show that (1) FasL is expressed in both neoplastic and reactive cells from a significant proportion of lymphoma cases, and (2) that the intratumoral FasL+/Fas+ reactive T cells are more sensitive to Fas-induced apoptosis than the neoplastic FasL+/Fas+ malignant B cells. A putative defect in the Fas/FasL pathway may thus favor the development of malignant B cell populations.