Clinical features of patients with nodal marginal zone lymphoma compared to follicular lymphoma: similar presentation, but differences in prognostic factors and rate of transformation

Transformations of marginal zone lymphomas and lymphoplasmacytic lymphomas: Report from the 2021 SH/EAHP Workshop

OBJECTIVES

To summarize the conclusions of the 2021 Society for Hematopathology/European Association for Haematopathology workshop regarding transformations of marginal zone lymphoma (MZL) and lymphoplasmacytic lymphoma (LPL).

METHODS

Nineteen cases were submitted to this portion of the workshop. Additional studies were performed in cases with sufficient material.

RESULTS

Cases included splenic MZL (n = 4), splenic diffuse red pulp small B-cell lymphoma (n = 2), nodal MZL (n = 4), extranodal MZL (n = 1), and LPL (n = 8). The most common transformation was to diffuse large B-cell lymphoma (DLBCL), but others included classic Hodgkin lymphoma, high-grade B-cell lymphomas with MYC and BCL6 rearrangements, plasmablastic lymphoma, and plasma cell leukemia. Two splenic MZLs with transformation to DLBCL contained t(14;19)(q32;q13.3) IGH::BCL3 rearrangements in both samples. Paired sequencing studies in 5 MZLs with transformation to clonally related DLBCL identified a variety of mutations and gene fusions at the time of transformation, including CARD11, IGH::MYC, NOTCH2, P2RY8, TBLX1X1, and IGH::CD274.

CONCLUSIONS

Marginal zone lymphoma and LPL may undergo a variety of transformation events, most commonly to DLBCL, which is usually, although not always, directly clonally related to the underlying low-grade lymphoma. Multiparameter analysis including broad-based sequencing studies can assist in the diagnosis and classification of these uncommon cases.

Follicular lymphoma t(14;18)-negative is genetically a heterogeneous disease

Fifty-five cases of t(14;18)- follicular lymphoma (FL) were genetically characterized by targeted sequencing and copy number (CN) arrays. t(14;18)- FL predominated in women (M/F 1:2); patients often presented during early clinical stages (71%), and had excellent prognoses. Overall, t(14;18)- FL displayed CN alterations (CNAs) and gene mutations carried by conventional t(14;18)+ FL (cFL), but with different frequencies. The most frequently mutated gene was STAT6 (57%) followed by CREBBP (49%), TNFRSF14 (39%), and KMT2D (27%). t(14;18)- FL showed significantly more STAT6 mutations and lacked MYD88, NOTCH2, MEF2B, and MAP2K1 mutations compared with cFL, nodal marginal zone lymphoma (NMZL), and pediatric-type FL (PTFL). We identified 2 molecular clusters. Cluster A was characterized by TNFRSF14 mutations/1p36 alterations (96%) and frequent mutations in epigenetic regulators, with recurrent loss of 6q21-24 sharing many features with cFL. Cluster B showed few genetic alterations; however, a subgroup with STAT6 mutations concurrent with CREBBP mutations/16p alterations without TNFRSF14 and EZH2 mutations was noted (65%). These 2 molecular clusters did not distinguish cases by inguinal localization, growth pattern, or presence of STAT6 mutations. BCL6 rearrangements were demonstrated in 10 of 45 (22%) cases and did not cluster together. Cases with predominantly inguinal presentation (20 of 50; 40%) had a higher frequency of diffuse growth pattern, STAT6 mutations, CD23 expression, and a lower number of CNAs, in comparison with noninguinal cases (5.1 vs 9.1 alterations per case; P < .05). STAT6 mutations showed a positive correlation with CD23 expression (P < .001). In summary, t(14;18)- FL is genetically a heterogeneous disorder with features that differ from cFL, NMZL, and PTFL.

Long-Term Observation of the Progression From Nodal Marginal Zone Lymphoma to Diffuse Large B-Cell Lymphoma in a Dog

A 4-year and 10-month old female Pembroke Welsh Corgi presented with an enlarged right popliteal lymph node, and a histopathological diagnosis of nodal marginal zone lymphoma (nMZL) was made. After resection of the lymph node, follow-up observation was continued without chemotherapy. At 22 months after initial presentation, the dog developed enlargement of peripheral lymph nodes, and the histopathological diagnosis was late-stage nMZL. Multidrug chemotherapy induced clinical complete remission, but the tumor relapsed with enlargement of peripheral and abdominal lymph nodes 42 months after initial presentation. Second-round multidrug chemotherapy induced complete clinical remission again; however, the tumor relapsed with lymphadenopathy 47 months after initial presentation. The dog died 59 months after initial presentation, and postmortem examination revealed generalized lymphadenopathy; the histopathological diagnosis was diffuse large B-cell lymphoma (DLBCL). Polymerase chain reaction for antigen receptor gene rearrangements revealed that the nMZL and DLBCL samples were derived from the same B-lymphocyte clone.

Deletion 20q12 is associated with histological transformation of nodal marginal zone lymphoma to diffuse large B-cell lymphoma

The genetic and molecular abnormalities underlying histological transformation (HT) of nodal marginal zone lymphoma (NMZL) to diffuse large B-cell lymphoma (DLBCL) are not well known. While del(20q12) is commonly deleted in myelodysplastic syndrome it has not previously been associated with DLBCL. We recently described a case of DLBCL harboring del(20q12) in a patient with a history of MZL involving lymph nodes and skin. Here we report eight matched cases of transformed MZL(tMZL): six from nodal MZL (tNMZL) and two from splenic MZL (tSMZL). We found >20% del(20q12) in 4/6 tNMZL, but not in tSMZL, nor in unmatched DLBCL, MZL with increased large cells (MZL-ILC), or MZL cases. To examine whether transformation is associated with a specific gene signature, the matched cases were analyzed for multiplexed gene expression using the Nanostring PanCancer Pathways panel. The differential gene expression signature revealed enrichment of inflammatory markers, as previously observed in MZL. Also, tMZL and de novo DLBCL were enriched for extracellular matrix proteins such as collagen and fibronectin, vascular development protein PDGFRβ, DNA repair protein RAD51, and oncogenic secrete protein Wnt11. A subset of genes is expressed differentially in del(20q12) tMZL cases vs non-del(20q12) tMZL cases. These results suggest a specific pathway is involved in the histological transformation of NMZL, which could serve as an indicator of aggressive clinical course in this otherwise indolent neoplasm.

IGHV mutational status of nodal marginal zone lymphoma by NGS reveals distinct pathogenic pathways with different prognostic implications

The precise B cell of origin and molecular pathogenesis of nodal marginal zone lymphoma (NMZL) remain poorly defined. To date, due to the rarity of NMZL, the vast majority of already-published studies have been conducted on a limited number of samples and the technical approach to analyze the immunoglobulin genes was of amplifying rearranged variable region genes with the classical direct sequencing of the PCR products followed by cloning. Here, we studied the B cell Ig heavy-chain repertoires by next-generation sequencing (NGS) in 30 NMZL cases. Most of the cases were mutated (20/28; 71.5%) with homologies to the respective germ line genes ranging from 85 to 97, 83%, whereas 8/28 (28.5%) were unmutated. In addition, our results show that NMZL cases have a biased usage of specific immunoglobulin heavy-chain variable (IGHV) region genes. Moreover, we documented intraclonal diversity in all (100%) of the mutated cases and ongoing somatic hypermutations (SHM) have been confirmed by hundreds of reads. We analyzed the mutational pattern to detect and quantify antigen selection pressure and we found a positive selection in 4 cases, whereas in the remaining cases there was an unspecific stimulation. Finally, the disease-specific survival and the progression-free survival were significantly different between cases with mutated and unmutated IGHV genes, pointing out mutational status as a possible new biomarker in NMZL.

Management of relapsed/refractory marginal zone lymphoma: focus on ibrutinib

Marginal zone lymphomas (MZLs) consist of a diverse family of malignancies, which are derived from B-cells. The disease subtypes are recognized extranodal, nodal, and splenic MZLs. The disease characteristics, clinical course, and treatment vary considerably based on the site of involvement. In 2017, the US Food and Drug Administration approved ibrutinib, a first in class Bruton’s tyrosine kinase inhibitor that revolutionized the care of chronic lymphocytic leukemia patients; for, the treatment of relapsed/refractory MZL based on pivotal open-label Phase II trial demonstrated an overall response rate of 48%, with a complete response rate of 3%, median progression-free survival of 14.2 months, and median overall survival not yet reached at a median follow-up of 19.4 months. In this review, we aim to summarize the current conundrums in the management of MZL and the evolving role of ibrutinib in the treatment of MZL.

Nodal marginal zone lymphoma: Clinical features, diagnosis, management and treatment

Nodular marginal zone lymphoma (NMZL) is a small B-cell lymphoma involving only lymph nodes and is the least common form of MZL constituting about 10% of cases. Patients usually present with advanced disease which must be distinguished from extranodal MZL with lymph node spread. NMZL shares cytological and immunophenotypic features with MALT and splenic MZL, but has a less favorable prognosis than these two categories. It occurs mostly in adults and pediatric cases are rare. Different therapeutic approaches have been used in NMZL, but because of the small patient numbers involved, more definitive treatment is still anticipated. Recent studies suggest that it probably represents a separate entity within the broader indolent lymphoma category. In NMZL there is an emerging need to utilize novel agents, already available for indolent lymphomas. Prospective studies are required to evaluate their therapeutic efficacy for NMZL in the future.

Transformation of marginal zone lymphoma (and association with other lymphomas)

Marginal zone lymphomas (MZL) are a diverse group of indolent lymphoproliferative disorders that comprise three subtypes: nodal, splenic and mucosal associated marginal zone lymphomas (MALT). Histologic transformation (HT) to an aggressive lymphoma is a rare event that can occur in any subtype, and at lower frequency compared to other indolent non Hodgkin lymphomas (NHL) like follicular lymphoma. There are few data directly associated with risk and prognosis of transformation in MZL. However, recent advances in the understanding of molecular and genetic features of MALT have contributed to an evolving appreciation of HT in this disease. Optimal treatment of HT of MZL remains unknown. Much of the approach to managing transformed MZL is extrapolated from other indolent NHLs.

The Comparative Diagnostic Features of Canine and Human Lymphoma

The non-Hodgkin lymphomas (NHLs) are a heterogeneous family of lymphoid malignancies that are among the most common neoplasms of both dogs and humans. Owing to shared molecular, signaling, incidence, and pathologic features, there is a strong framework supporting the utilization of canine lymphoma as a comparative, large animal model of human NHL. In alignment with the biologic similarities, the current approach towards the diagnosis and classification of canine lymphoma is based upon the human World Health Organization guidelines. While this approach has contributed to an increasing appreciation of the potential biological scope of canine lymphoma, it has also become apparent that the most appropriate diagnostic philosophy must be multimodal, namely by requiring knowledge of microscopic, immunophenotypic, and clinical features before establishing a final disease diagnosis. This review seeks to illustrate the comparative similarities and differences in the diagnosis of canine lymphoma through the presentation of the microscopic and immunophenotypic features of its most common forms.