A Combined Biomarker of Bright CD38 and MYC ≥55% Is Highly Predictive of Double-/Triple-Hit High-Grade B-Cell Lymphoma

Clinicopathologic features of relapsed CD19(-) B-ALL in CD19-targeted immunotherapy: Biological insights into relapse and LILRB1 as a novel B-cell marker for CD19(-) B lymphoblasts

INTRODUCTION

The mechanism of relapsed CD19(-) B-ALL after anti-CD19 immunotherapy (Kymriah [CART-19] and blinatumomab) is under active investigation. Our study aims to assess LILRB1 as a novel B-cell marker for detecting CD19(-) B-lymphoblasts and to analyze the clinicopathologic/genetic features of such disease to provide biological insight into relapse.

METHODS

Six patients (3 males/3 females, median age of 14 years) with relapsed CD19(-) B-ALL were analyzed for cytogenetic/genetic profile and immunophenotype.

RESULTS

CD19(-) B-ALL emerged after an interval of 5.8 months following anti-CD19 therapy. Five of six patients had B-cell aplasia, indicative of a persistent effect of CART or blinatumomab at relapse. Importantly, LILRB1 was variably expressed on CD19(-) and CD19(+) B lymphoblasts, strong on CD34(+) lymphoblasts and dim/partial on CD34(-) lymphoblasts. Three of six patients with paired B-ALL samples (pre- and post-anti-CD19 therapy) carried complex and different cytogenetic abnormalities, either as completely different or sharing a subset of cytogenetic abnormalities.

CONCLUSION

LILRB1 can be used as a novel B-cell marker to identify CD19(-) B lymphoblasts. The emergence of CD19(-) B-ALL appears to be associated with complex cytogenetic evolutions. The mechanism of CD19(-) B-ALL relapse under anti-CD19 immune pressure remains to be explored by comprehensive molecular studies.

RNASeq Analysis for Accurate Identification of Fusion Partners in Tumor Specific Translocations Detected by Standard FISH Probes in Hematologic Malignancies

Background

Fluorescence labeled DNA probes and in situ hybridization methods had shorter turn round time for results revolutionized their clinical application. Signals obtained from these probes are highly specific, yet they can produce fusion signals not necessarily representing fusion of actual genes due to other genes included in the probe design. In this study we evaluated discordance between cytogenetic, FISH and RNAseq results in 3 different patients with hematologic malignancies and illustrated the need to perform next generation sequencing (NGS) or RNASeq to accurately interpret FISH results.

Methods

Bone marrow or peripheral blood karyotypes and FISH were performed to detect recurring translocations associated with hematologic malignancies in clinical samples routinely referred to our clinical cytogenetics laboratory. When required, NGS was performed on DNA and RNA libraries to detect somatic alterations and gene fusions in some of these specimens. Discordance in results between these methods is further evaluated.

Results

For a patient with plasma cell leukemia standard FGFR3 / IGH dual fusion FISH assay detected fusion that was interpreted as FGFR3-positive leukemia, whereas NGS/RNASeq detected NSD2::IGH. For a pediatric acute lymphoblastic leukemia patient, a genetic diagnosis of PDGFRB-positive ALL was rendered because the PDGFRB break-apart probe detected clonal rearrangement, whereas NGS detected MEF2D::CSF1R. A MYC-positive B-prolymphocytic leukemia was rendered for another patient with a cytogenetically identified t(8;14) and MYC::IGH by FISH, whereas NGS detected a novel PVT1::RCOR1 not previously reported.

Conclusions

These are 3 cases in a series of several other concordant results, nevertheless, elucidate limitations when interpreting FISH results in clinical applications, particularly when other genes are included in probe design. In addition, when the observed FISH signals are atypical, this study illustrates the necessity to perform complementary laboratory assays, such as NGS and/or RNASeq, to accurately identify fusion genes in tumorigenic translocations.

Double/triple hit lymphoma in the gastrointestinal tract: clinicopathological features, PD-L1 expression and screening strategy

We aimed to detect the clinicopathological features and immune microenvironment of double-hit/triple-hit lymphoma in the gastrointestinal tract (GI-DHL/THL) and identify the best diagnostic strategies. A total of 114 cases, including 15 GI-DHL/THL, 42 non-GI-DHL/THL and 57 control diffuse large B-cell lymphoma (DLBCL) cases, were comparatively analyzed for their clinicopathological characteristics, the expression of the immune-regulatory checkpoint PD-L1 and immune microenvironment. We applied univariate and multivariate analyses to determine predictors of DHL/THL. GI-DHL/THL patients showed a higher prevalence of previous infection with hepatitis B virus (HBV) than those with GI-DLBCL. Morphologically, 87% of cases exhibited features of DLBCL. Regarding immunohistochemistry results, the MYC protein expression and the Ki-67 proliferation index were significantly higher in the GI-DHL/THL group than in the GI-DLBCL group. The main source of PD-L1 expression in DHL was tumor-associated macrophages, whereas some tumor cells were positive for PD-L1 in GI-DLBCL cases, as determined through multiplex immunofluorescence staining. The multivariable logistic analysis suggested that 5 variables, namely, age, Mum1, CD10, MYC, and HBV infection status, reflect the risk of DHL/THL. The GI-DHL/THL group show different clinicopathological features and immune microenvironments from DLBCL, which might suggest that different signaling pathways are involved. More work is needed to elucidate the pathogenic mechanism of GI-DHL/THL.