Lymphoid enhancer binding factor 1 (LEF1) expression is significantly higher in Hodgkin lymphoma associated with Richter syndrome relative to de novo classic Hodgkin lymphoma

Diagnostic utility of lymphocyte enhancer factor 1 in aggressive B-cell lymphoma with MYC rearrangement

OBJECTIVES

We sought to investigate the diagnostic value of lymphocyte enhancer factor 1 (LEF1) expression in aggressive B-cell lymphomas (BCL) with MYC gene rearrangement (MYC-R).

METHODS

Sixty-seven cases of BCL were studied and included Burkitt lymphoma (BL) (23 cases); diffuse large B-cell lymphoma (DLBCL), not otherwise specified (NOS) with MYC-R (13 cases); and DLBCL/high-grade B-cell lymphoma with MYC, BCL2, and/or BCL6 rearrangements (double-hit [DH] or triple-hit [TH], 17 cases). Random DLBCL-NOS (14 cases) without MYC-R was recruited as a control group. By immunohistochemical stains, 3 patterns of LEF1 staining were recorded as pattern 0 (negative), pattern 1 (weak and heterogeneous staining, <80%), and pattern 2 (moderate/strong and uniform staining, ≥80%).

RESULTS

Pattern 1 can be seen in all BCLs with MYC-R included in this study and more commonly seen in DLBCL without MYC-R (8/14 cases). Pattern 2 is characteristic (positive predictive value = 86%) for Epstein-Barr virus (EBV)-negative BL, while pattern 0 was seen in 22 (76%) of 29 cases of DLBCL-MYC-R/DH/TH (P < .001). Seven of 8 EBV-positive BL cases showed pattern 0, which was completely opposite to the common pattern 2 in EBV-negative BL (12/15 cases). Pattern 2 was not detected in all DH/TH cases.

CONCLUSIONS

Weak and heterogeneous staining of LEF1 can be seen in all the BCLs with and without MYC-R. Strong and uniform staining of LEF1 is highly characteristic of EBV-negative BL among all aggressive BCLs with MYC-R, while the negative staining of LEF1 is mostly suggestive of DLBCL-MYC-R/DH/TH. Lymphocyte enhancer factor 1 provides additional diagnostic value in the differentiation of BL from other aggressive BCLs with MYC-R, especially in a limited specimen.

Immunophenotypic and genomic landscape of Richter transformation diffuse large B-cell lymphoma

Integrated clinicopathological and molecular analyses of Richter transformation of diffuse large B-cell lymphoma subtype (RT-DLBCL) cases remain limited. This study group included 142 patients with RT-DLBCL. Morphological evaluation and immunophenotyping, using immunohistochemistry and/or multicolour flow cytometry, were performed. The results of conventional karyotyping, fluorescence in situ hybridisation analysis and mutation profiling performed using next generation sequencing were reviewed. Patients included 91 (64.1%) men and 51 (35.9%) women with a median age of 65.4 years (range 25.4-84.9 years) at the time of RT-DLBCL diagnosis. Patients had CLL for a median of 49.5 months (range 0-330 months) before onset of RT-DLBCL. Most cases (97.2%) of RT-DLBCL had immunoblastic (IB) morphology, the remainder had a high grade morphology. The most commonly expressed markers included: CD19 (100%), PAX5 (100%), BCL2 (97.5%), LEF1 (94.7%), CD22 (90.2%), CD5 (88.6%), CD20 (85.7%), CD38 (83.5%), MUM1 (83.3%), CD23 (77%) and MYC (46.3%). Most (51/65, 78.4%) cases had a non-germinal centre B-cell immunophenotype. MYC rearrangement was detected in 9/47 (19.1%) cases, BCL2 rearrangement was detected in 5/22 (22.7%) cases, and BCL6 rearrangement was detected in 2/15 (13.3%) cases. In comparison to CLL, RT-DLBCL had higher numbers of alterations involving chromosomes 6, 17, 21, and 22. The most common mutations detected in RT-DLBCL involved TP53 (9/14, 64.3%), NOTCH1 (4/14, 28.6%) and ATM (3/14, 21.4%). Among RT-DLBCL cases with mutant TP53, 5/8 (62.5%) had TP53 copy number loss, and among those, such loss was detected in the CLL phase of the disease in 4/8 (50%) cases. There was no significant difference in overall survival (OS) between patients with germinal centre B-cell (GCB) and non-GCB RT-DLBCL. Only CD5 expression correlated significantly with OS (HR=2.732; 95% CI 1.397-5.345; p=0.0374). RT-DLBCL has distinctive morphological and immunophenotypic features, characterised by IB morphology and common expression of CD5, MUM1 and LEF1. Cell-of-origin does not seem to have prognostic implications in RT-DLBCL.

Aberrant Expression of Lymphoid Enhancer-Binding Factor 1 (LEF1) in Hodgkin Lymphoma

Lymphoid enhancer-binding factor 1 (LEF1) is a transcription factor involved in T-cell maturation and is usually absent in mature B-cells. Previous studies have shown aberrant LEF1 expression as a sensitive and specific marker in chronic lymphocytic leukemia/small lymphocytic lymphoma. Our primary aims were i) to analyze LEF1 expression in classic Hodgkin lymphomas (CHL) including de novo and Richter syndrome (RS), and to assess if LEF1 can be a surrogate marker to assess clonal relationship in RS, and ii) to compare LEF1 expression in CHL and Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL). We included 117 patients: 24 CHL-RS, 66 CHL-de novo and 27 NLPHL. There was no significant difference in LEF1 expression between CHL-RS and CHL-de novo (79.2% vs 87.9%, P = 0.299), or in type I and type II CHL-RS (75% vs 81.3%, P = 1.000). However, CHL showed a significantly higher LEF1 expression compared to NLPHL (85.6% vs 44.4%, P<0.0001). As the Wnt/β-catenin pathway directly regulates LEF1 expression in a β-catenin-dependent way, β-catenin expression was assessed in 76 cases and all were negative. Additionally, no association between EBV-positivity and LEF1-expression was detected. Overall, our findings show high LEF1 expression in CHL, regardless of RS or de novo, indicating LEF1 cannot be utilized as a surrogate marker to suggest clonal relationship in RS. Compared with CHL, LEF1 expression is significantly less common in NLPHL, further attesting that they are biologically distinct entities. The absent β-catenin expression suggests LEF1 expression is independent of Wnt/β-catenin signaling pathway in Hodgkin lymphomas.

Geographic Variability of Nodular Lymphocyte-Predominant Hodgkin Lymphoma

OBJECTIVES

Nodular lymphocyte-predominant Hodgkin lymphoma (NLPHL) differs from classic Hodgkin lymphoma (CHL) in terms of clinicopathologic features, including Epstein-Barr virus (EBV) association. CHL geographic variability is well known, with higher frequencies of mixed-cellularity subtype and EBV positivity in low/middle-income countries (LMICs), but there are few well-characterized series of NLPHL from LMICs.

METHODS

We detail clinicopathologic findings of 21 NLPHL cases received in consultation from Kenya and summarize reports of NLPHL with EBV testing published since 2000.

RESULTS

Median age of consultation cases was 36 years, and male/female ratio was 3.2. All cases involved peripheral lymph nodes and showed at least some B-cell-rich nodular immunoarchitecture, with prominent extranodular lymphocyte-predominant (LP) cells and T-cell-rich variant patterns most commonly seen. LP cells expressed pan-B-cell markers, including strong OCT2; lacked CD30 and CD15 expression in most cases; and were in a background of expanded/disrupted follicular dendritic cell meshworks and increased T-follicular helper cells. LP cells were EBV negative in 18 cases. Historical cases showed a low rate of EBV positivity with no significant difference between LMICs and high-income countries.

CONCLUSIONS

Unlike CHL, NLPHL shows few geographic differences in terms of clinicopathologic features and EBV association. These findings have implications for diagnosis, prognostication, and treatment of patients with NLPHL in LMICs.