Aggressive B-cell lymphomas: a review based on the workshop of the XI Meeting of the European Association for Haematopathology

High-grade Follicular Lymphomas Exhibit Clinicopathologic, Cytogenetic, and Molecular Diversity Extending Beyond Grades 3A and 3B

Although follicular lymphoma (FL) is usually graded as FL1-2, FL3A, and FL3B, some borderline cases can be observed and led us to investigate the clinicopathologic diversity of grade 3 FL (FL3). Among 2449 FL patients enrolled in Lymphoma Study Association (LYSA) trials, 1921 cases with sufficient material underwent a central pathologic review. The resulting diagnoses comprised 89.6% FL1-2 (n=1723), 7.2% FL3A (n=138), and 0.5% purely follicular FL3B (n=9). The remaining 51 unclassifiable cases (2.7%) exhibited high-grade features but did not meet WHO criteria for either FL3A or FL3B; and were considered as "unconventional" high-grade FL (FL3U). FL3U morphological pattern consisted of nodular proliferation of large cleaved cells or small-sized to medium-sized blast cells. Compared with FL3A, FL3U exhibited higher MUM1 and Ki67 expression, less BCL2 breaks and more BCL6 rearrangements, together with a higher number of cases without any BCL2, BCL6 or MYC rearrangement. FL3U harbored less frequent mutations in BCL2, KMT2D, KMT2B, and CREBBP than FL3A. MYC and BCL2 were less frequently mutated in FL3U than FL3B. Rituximab cyclophosphamide, doxorubicin, vincristine, and prednisone treated FL3U patients had a worse survival than FL1-2 patients with similar follicular lymphoma international prognostic index and treatment. These results suggest that high-grade FLs encompass a heterogeneous spectrum of tumors with variable morphology and genomic alterations, including FL3U cases that do not strictly fit WHO criteria for either FL3A or FL3B, and display a worse outcome than FL1-2. The distinction of FL3U may be useful to allow a better comprehension of high-grade FLs and to design clinical trials.

Similar prognosis of transformed and de novo diffuse large B-cell lymphomas in patients treated with immunochemotherapy

BACKGROUND

The prognosis of diffuse large B-cell lymphomas (DLBCL) transformed from indolent lymphoma (TL) has been considered poorer than that of de novo DLBCL. However, it seems to have improved since the introduction of rituximab.

PATIENTS AND METHODS

We compared the characteristics (including the cell-of-origin), and the prognosis of 29 patients with TL and 101 with de novo DLBCL treated with immunochemotherapy.

RESULTS

Patients with TL and de novo DLBCL had similar characteristics. All TL cases evolving from follicular lymphoma were germinal-center B-cell-like, while those TL from marginal zone lymphoma or chronic lymphocytic leukemia were non-germinal-center B-cell-like. The complete response rate was similar in TL and de novo DLBCL (62 vs. 66%, P=.825). The 5-year overall and progression-free survival probabilities (95% CI) were 59% (40-78) and 41% (22-60) for TL and 63% (53-73) and 60% (50-70) for de novo DLBCL, respectively (P=.732 for overall survival and P=.169 for progression-free survival).

CONCLUSION

In this study, the prognosis of TL and de novo DLBCL treated with immunochemotherapy was similar. The role of intensification with stem cell transplantation in the management of TL may be questionable in the rituximab era.

[Primary mediastinal large B-cell lymphoma in women: about five cases]

Primary mediastinal large B-cell lymphoma (PMBL) is a lymphoma occurring in the anterior mediastinum starting from the cells B of the thymique medullary zone. This is a rare entity characterized by epidemiological, clinical and evolutionary peculiarities as well as by pathological and immunohistochemical peculiarities. We report a case series of 5 patients with diagnosed PMBL hospitalized in Pulmonology Department of Ibn Sina Hospital between January 2012 and May 2016. The average age was 34 years, the median of consultation time was 2 months. Reported symptoms were dyspnea, chest pain, dry cough; two patients suffered from superior vena cava syndrome. LDH level was high in 4 patients. Thoracic imaging showed an anterior mediastinal tissue processing in 5 patients. Histological diagnosis was based on ultrasound-guided transparietal puncture biopsy in 5 patients. The contribution of immunohistochemistry was decisive in all cases. Patients were sent to the National Institute of Oncology for therapeutic management. PMBL prognosis is reserved, it most commonly occurs in young women, which increases the need of aggressive therapy to improve survival rate.

High-grade B cell lymphoma, unclassifiable, with blastoid features: an unusual morphological subgroup associated frequently with BCL2 and/or MYC gene rearrangements and a poor prognosis

AIMS

A subset of B cell lymphomas with blastoid features do not fit either as B lymphoblastic lymphoma/leukaemia or blastoid mantle cell lymphoma. Their classification is challenging, even with complete clinicopathological and genetic information. At a haematopathology workshop, experts had suggested the term 'high-grade B cell lymphoma, unclassifiable, with blastoid features', and recommended further studies.

METHODS AND RESULTS

We describe the clinicopathological, immunophenotypic and cytogenetic findings of 24 high-grade B cell lymphomas, unclassifiable, with blastoid features. Fifteen patients presented de novo and seven patients had a history of lymphoma. Twenty patients (83%) presented with nodal disease. All tumours expressed pan-B cell antigens and 17 (89%) of 19 tumours assessed had a germinal centre B cell immunophenotype. Ten (63%) of 16 tumours assessed by fluorescence in-situ hybridization (FISH) had MYC rearrangement, 13 of 18 (72%) carried IGH-BCL2 and nine of 15 (60%) had both (double-hit lymphoma). The median overall survival was 1.1 years. Using 2008 World Health Organization criteria, 15 cases were classified as B cell lymphoma, unclassifiable, with features intermediate between diffuse large B cell lymphoma (DLBCL) and Burkitt lymphoma, and nine as DLBCL, small centroblastic variant.

CONCLUSION

High-grade B cell lymphomas, unclassifiable, with blastoid features are clinically aggressive with poor survival. Most neoplasms have a germinal centre B cell phenotype. MYC rearrangements and IGH-BCL2 are common, and ~60% are double-hit lymphomas.

Comparison of outcomes after allogeneic hematopoietic stem cell transplantation in patients with follicular lymphoma, diffuse large B-cell lymphoma associated with follicular lymphoma, or de novo diffuse large B-cell lymphoma

The outcome after allogeneic hematopoietic stem cell transplantation (allo-HCT) for diffuse large B-cell lymphoma (DLBCL) associated with follicular lymphoma (FL), which includes DLBCL with pre- or co-existing FL, remains controversial, and few previous reports have compared the outcomes after allo-HCT for FL, DLBCL associated with FL, and de novo DLBCL. We retrospectively analyzed 97 consecutive patients with FL (n = 46), DLBCL associated with FL (n = 22), or de novo DLBCL (n = 29) who received allo-HCT at our institute between 2000 and 2010. With a median follow-up of 53 months, the 5-year overall survival (OS) and progression-free survival (PFS) were, respectively, 77% and 70% for FL, 62% and 57% for DLBCL associated with FL, and 26% and 23% for de novo DLBCL. The 5-year cumulative incidences of non-relapse mortality and disease progression/relapse were, respectively, 16% and 15% for FL, 19% and 24% for DLBCL associated with FL, and 36% and 41% for de novo DLBCL. By a multivariate analysis, the OS and PFS for DLBCL associated with FL were significantly better than those for de novo DLBCL, whereas they were not significantly different from those for FL. These results suggest that allo-HCT may be a promising option for patients with not only advanced FL but also DLBCL associated with FL.

Subsequent development of diffuse large B-cell lymphomas and Hodgkin lymphoma associated with primary immune disorder in a 6-year-old female: a case report and review of the literature

Neoplastic lymphoid proliferation may arise from immune deficiency or disordered regulation of the immune system. Often the neoplasms are associated with viral agents, such as Epstein-Barr virus, human immunodeficiency virus, or human herpes virus 8. Lymphoproliferative diseases have been documented in a variety of primary immune disorders. The most commonly encountered neoplastic lesion is diffuse large B-cell lymphoma (DLBCL), although Hodgkin lymphoma (HL), Burkitt lymphoma, and peripheral T-cell lymphomas and/or leukemias have also been documented in rare instances. We report a case of a 6-year-old girl with unclassifiable primary immunodeficiency diagnosed with 2 different clones of DLBCLs and subsequently developed lymphocyte-depleted, classical HL. Both neoplasms were associated with Epstein-Barr virus. To the best of our knowledge, this is the first reported occurrence of primary immune disorder-associated lymphoproliferative disease with sequential development of DLBCLs and HL in a pediatric patient. Thorough surveillance is paramount for accurate assessment of the associated lymphoproliferative disease and in ascertaining likely transformation to, or de novo evolution of a different lymphoid neoplasm. This is also important in evaluating treatment response with appropriate therapeutic adjustments if clinically indicated.

[Primary mediastinal large B-cell lymphoma: histopathologic features. A specific tumour]

The diffuse large B-cell lymphomas of the mediastinum were long considered to be a variant of the classic forms of large B-cell lymphomas. However, their clinical and radiological features and especially their histopathological variants point to other lymphoid tumours such as Hodgkin's disease or anaplastic lymphomas, thymic tumours, germ cell tumours or metastatic tumors. The immunohistochemical findings are of prime importance in the diagnosis. This has recently been completed by molecular studies. Currently, they represent a distinct entity among the large B-cell lymphomas, due to their clinical, pathological and molecular features as well as the outcome. The authors report a new case in a young man.

Commentary on the WHO classification of tumors of lymphoid tissues (2008): "Gray zone" lymphomas overlapping with Burkitt lymphoma or classical Hodgkin lymphoma

The 2008 WHO Classification of Tumors of Haematopoietic and Lymphoid Tissues has introduced two new categories of high-grade B-cell lymphomas: entities in which features of diffuse large B-cell lymphoma (DLBCL) overlap with Burkitt lymphoma (DLBCL/BL) or classical Hodgkin lymphoma (DLBCL/HL). The DLBCL/BL category encompasses cases that resemble Burkitt lymphoma morphologically, but have one or more immunophenotypic or molecular genetic deviations that would exclude it from the BL category; conversely, some cases have immunophenotypic and/or genetic features of BL, but display cytologic variability unacceptable for BL. Many of the cases in the DLBCL/BL category contain a translocation of MYC as well as either BCL2 or BCL6 (so-called double-hit lymphomas) and have a very aggressive clinical behavior. The DLBCL/HL category encompasses lymphomas that exhibit the morphology of classical Hodgkin lymphoma but the immunophenotype of DLBCL, or vice versa. Most DLBCL/HL cases described present as mediastinal masses, but this category is not limited to mediastinal lymphomas. These new categories acknowledge the increasing recognition of cases that display mixed features of two well-established diseases. Whether the existence of such cases reflects shortcomings of our current diagnostic armamentarium or a true disease continuum in which such hybrid or intermediate neoplasms actually exist remains to be determined.

Diffuse large B-cell lymphoma after transformation from low-grade follicular lymphoma: morphological, immunohistochemical, and FISH analyses

Follicular lymphoma (FL) is one of the most common subtypes of non-Hodgkin lymphoma and frequently transforms to diffuse large B-cell lymphoma (DLBCL). To clarify some aspects of the natural history of FL, we retrospectively examined 43 consecutive patients who had DLBCL with pre- or coexisting FL grade 1 or 2. The patients comprised 22 men and 21 women with a median age of 53 years. Most of the patients (34/43) showed advanced-stage (III or IV) disease initially. We examined both FL and DLBCL components morphologically, immunohistochemically, and by interface fluorescence in situ hybridization (FISH: IGH/BCL2 fusion, BCL6 translocation) analysis. Most of the DLBCLs were classified as the centroblastic subtype, with two exceptions of the anaplastic subtype. Immunohistochemical analysis of both the FL and DLBCL components revealed the following respective positivity rates: CD20 100%/100%, CD10 86%/66%, Bcl-2 96%/91%, Bcl-6 84%/88%, MUM1 16%/34%, CD30 0%/20%, CD138 0%/0%, and CD5 0%/3%. Loss of CD10 (6/36, 17%) and gain of MUM1 (7/28, 25%) and CD30 (5/21, 24%) through transformation were not infrequent. High positivity rates for Bcl-2 and Bcl-6 were maintained throughout transformation. Among the DLBCLs, 84% were classified as the germinal center B-cell phenotype (GCB) and 16% as non-GCB in accordance with the criteria of Hans et al. IGH/BCL2 fusion was detected by FISH in 89% of FLs and 82% of DLBCLs. BCL6 translocation was detected in 1/6 (17%) DLBCLs without IGH/BCL2 fusion. Thus, although the morphological features and FISH results for DLBCL were consistent with transformed FL, the immunophenotype showed wide heterogeneity.

The B cell antigen receptor and overexpression of MYC can cooperate in the genesis of B cell lymphomas

A variety of circumstantial evidence from humans has implicated the B cell antigen receptor (BCR) in the genesis of B cell lymphomas. We generated mouse models designed to test this possibility directly, and we found that both the constitutive and antigen-stimulated state of a clonal BCR affected the rate and outcome of lymphomagenesis initiated by the proto-oncogene MYC. The tumors that arose in the presence of constitutive BCR differed from those initiated by MYC alone and resembled chronic B cell lymphocytic leukemia/lymphoma (B-CLL), whereas those that arose in response to antigen stimulation resembled large B-cell lymphomas, particularly Burkitt lymphoma (BL). We linked the genesis of the BL-like tumors to antigen stimulus in three ways. First, in reconstruction experiments, stimulation of B cells by an autoantigen in the presence of overexpressed MYC gave rise to BL-like tumors that were, in turn, dependent on both MYC and the antigen for survival and proliferation. Second, genetic disruption of the pathway that mediates signaling from the BCR promptly killed cells of the BL-like tumors as well as the tumors resembling B-CLL. And third, growth of the murine BL could be inhibited by any of three distinctive immunosuppressants, in accord with the dependence of the tumors on antigen-induced signaling. Together, our results provide direct evidence that antigenic stimulation can participate in lymphomagenesis, point to a potential role for the constitutive BCR as well, and sustain the view that the constitutive BCR gives rise to signals different from those elicited by antigen. The mouse models described here should be useful in exploring further the pathogenesis of lymphomas, and in preclinical testing of new therapeutics.

It has long been suspected that the malignant proliferation of B lymphocytes known as lymphomas might represent a perversion of how the cells normally respond to antigen. In particular, the molecular receptor on the surface of the cells that signals the presence of antigen might be abnormally active in lymphomas. We have tested this hypothesis by engineering the genome of mice so that virtually all of the B cells are commandeered by a single version of the surface receptor, then stimulated that receptor with the molecule it is designed to recognize. Our results indicate that both the unstimulated and stimulated states of the receptor can cooperate with an oncogene known as MYC in the genesis of lymphomas. But the two states of the receptor give rise to different forms of lymphoma. In particular, the stimulated form cooperates with MYC to produce a disease that closely resembles Burkitt lymphoma. These results illuminate the mechanisms that are responsible for lymphomas and could inform the development of new strategies to treat the disease.

A series of genetically engineered mice were used to substantiate a long-standing speculation that chronic immune-stimulus may be involved in the genesis of certain lymphomas, illuminating the pathogenesis of B cell lymphomas and suggesting new strategies to treat several forms of this malignancy, including Burkitt lymphoma.

Presence of simian virus 40 in diffuse large B-cell lymphomas in Tunisia correlates with germinal center B-cell immunophenotype, t(14;18) translocation, and P53 accumulation

Previously we have reported the presence of simian virus 40 DNA in 56% of diffuse large B-cell lymphomas in Tunisia. Here, we investigated the relationship between the status of simian virus 40 and t(14;18) translocation, germinal center status, and P53 and BCL2 expression to assess the clinical and biological relevance of simian virus 40 presence in diffuse large B-cell lymphomas. Therefore, we evaluated by immunohistochemistry the expression patterns of CD10, BCL6, MUM1, BCL2, and P53 in 86 diffuse large B-cell lymphomas (48 simian virus 40-positive and 38 simian virus 40-negative cases). The t(14;18) translocation was investigated by polymerase chain reaction. Immunostaining patterns for CD10, BCL6, and MUM1 were used to subclassify diffuse large B-cell lymphoma cases as germinal center or non-germinal center phenotypes. Germinal center phenotype, t(14;18), P53, and BCL2 expression were found in 71, 30, 55, and 65% of cases, respectively. Interestingly, germinal center phenotype, t(14;18), and P53 accumulation were found to be more frequent in simian virus 40-positive cases than in simian virus 40-negative ones (81, 44, 69 vs 58, 13, 37%; P=0.018, 0.002, and 0.003, respectively). However, there were no correlations between the presence of simian virus 40 and the expression of CD10, BCL6, MUM1 and BCL2, patient's age and gender, clinical stage, or the International Prognosis Index. Multivariate logistic regression analyses revealed that the germinal center phenotype, P53 accumulation, and t(14;18) were independent factors for simian virus 40 association (P=0.029, 0.006, and 0.014, respectively). There were no significant differences in overall survival regarding P53, BCL2, or t(14;18) status. However, patients with germinal center phenotype or low International Prognosis Index scores displayed a significantly better survival than those with non-germinal center phenotype or high International Prognosis Index scores (P=0.003 and 0.0001, respectively). These two prognosis factors remain independent in multivariate analyses (P=0.001 and <0.0001, respectively). Interestingly, among patients with germinal center phenotype, simian virus 40-positive subgroup displayed a significantly shorter survival than simian virus 40-negative subgroup (P=0.034). In summary, these findings support a role of simian virus 40 in the pathogenesis of diffuse large B-cell lymphomas. On other hand, they suggest that a significant proportion of diffuse large B-cell lymphoma cases with germinal center phenotype may result from early transformation by simian virus 40, mainly those harboring the t(14;18). Modern Pathology (2008) 21, 282-296; doi:10.1038/modpathol.3800993; published online 28 December 2007.

Burkitt lymphoma in adults

This review will begin with a detail of the revision of the WHO classification, and pathological definitions of Burkitt lymphoma. Over the past several years, molecular understanding of Burkitt lymphoma has improved significantly. Using gene expression profiling, a genomic "signature" of Burkitt lymphoma may be identified, that has fidelity beyond c-myc expression, and the presence of the classical t(8;14). Then, evaluation and therapy of the adult patient with Burkitt lymphoma will be reviewed. Relatively few data exist on optimal therapy of the adult patient with Burkitt lymphoma. Principles of therapy should include high doses of alkylating agents, frequent administration of chemotherapy, and attention to central nervous system (CNS) prophylaxis with high doses of systemic chemotherapy, intrathecal therapy, or both. The outcome of adult patients with Burkitt lymphoma, particularly those over 40 years of age, is inferior to the outcome of younger patients, but may be improving over the past few years. Results from an international collaborative effort, which are helpful in evaluating results of Burkitt lymphoma therapy in adults, will be presented. HIV-associated Burkitt lymphoma, and elderly patients with Burkitt lymphoma, comprise special clinical situations that will be also covered in this review.

Update on extranodal lymphomas. Conclusions of the Workshop held by the EAHP and the SH in Thessaloniki, Greece

Classification and proper treatment of extranodal lymphoma is hindered by the diversity of lymphoma types and the relative rarity of many of these tumour types. In order to review controversial issues in extranodal lymphoma diagnosis, a joint Workshop of the European Haematopathology Association (EAHP) and the Society for Hematopathology (SH) was held, where 99 selected cases were reviewed and discussed. This Workshop summary is focused on the most controversial aspect of cutaneous B-cell lymphoma, other extranodal B-cell lymphomas, plasmablastic lymphoma and anaplastic large-cell lymphoma in extranodal sites, and makes practical recommendations about diagnosis and therapeutic approaches.

Diffuse large B-cell lymphomas with plasmablastic differentiation

Recent evidence suggests that diffuse large B-cell lymphoma (DLBCL) with plasmablastic differentiation represents a clinically heterogeneous spectrum with different clinicopathologic characteristics representing distinct entities. Subtypes of DLBCL with plasmablastic features and terminal B-cell differentiation include plasmablastic lymphoma (PBL) of oral mucosa type; PBL with plasmacytic differentiation; primary effusion lymphoma (PEL); KSHV-positive solid lymphoma/extracavitary PEL/HHV-8 associated DLBCL; and DLBCL expressing ALK. In contrast, PBL associated with multicentric Castleman disease, DLBCL with secretory differentiation, pyothorax-associated lymphoma, and atypical Burkitt lymphoma with plasmacytoid differentiation have morphologic appearances of plasma cell differentiation but maintain a mature B-cell (CD20 positive) phenotype. These tumors as well as extramedullary plasmablastic tumors secondary to multiple myeloma or plasmacytomas are included in the differential diagnosis. In this review, we discuss recently described clinicopathologic insights, case observations, and recently reported molecules involved in terminal B-cell or plasma cell differentiation and their possible roles in disease pathogenesis.

Non-mediastinal grey zone lymphomas and report from the workshop

Grey zone lymphomas represent borderline lesions between classical Hodgkin lymphoma (cHL) and other morphologically and immunophenotypically related diseases and entities like nodular lymphocyte predominant HL, T-cell rich B-cell lymphoma, ALK-negative anaplastic large cell lymphoma (ALCL), diffuse large B cell lymphoma (DLBCL) anaplastic variant and primary mediastinal LBCL. The sharp definition of morphological, immunophenotypical and molecular features of the "text-book cases" of each disease and the comparison with grey zone cases has reduced most of the latter cases. Two reports in this workshop dealt with the problematic non-mediastinal grey zone lymphomas, one with a cHL of T cell-type presenting in the skin as a ALK-negative ALCL and the other with the grey zone between cHL of B-cell type and ALK-negative ALCL.