Multicolour and lineage-specific interphase chromosome Flow-FISH: method development and clinical validation.

Flow cytometry can be applied in the detection of fluorescence in situ hybridisation (FISH) signals to efficiently analyse chromosomal aberrations. However, such interphase chromosome (IC) Flow-FISH protocols are currently limited to detecting a single colour. Furthermore, combining IC Flow-FISH with conventional multicolour flow cytometry is difficult because the DNA-denaturation step in FISH assay also disrupts cellular integrity and protein structures, precluding subsequent antigen-antibody binding and hindering concurrent labeling of surface antigens and FISH signals. We developed a working protocol for concurrent multicolour flow cytometry detection of nuclear IC FISH signals and cell surface markers. The protocol was validated by assaying sex chromosome content of blood cells, which was indicative of chimerism status in patients who had received sex-mismatched allogeneic haematopoietic stem cell transplants (allo-HSCT). The method was also adapted to detect trisomy 12 in chronic lymphocytic leukaemia (CLL) subjects. We first demonstrated the feasibility of this protocol in detecting multiple colours and concurrent nuclear and surface signals with high agreement. In clinical validation experiments, chimerism status was identified in clinical samples (n=56) using the optimised IC Flow-FISH method; the results tightly corresponded to those of conventional slide-based FISH (R2=0.9649 for XX cells and 0.9786 for XY cells). In samples from patients who received sex-mismatched allo-HSCT, individual chimeric statuses in different lineages could be clearly distinguished with high flexibility in gating strategies. Furthermore, in CLL samples with trisomy 12, this method could demonstrate that enriched trisomy 12 FISH signal was present in B cells rather than in T cells. Finally, by performing combined labelling of chromosome 12, X chromosome, and surface markers, we could detect rare residual recipient CLL cells with trisomy 12 after allo-HSCT. This adaptable protocol for multicolour and lineage-specific IC Flow-FISH advances the technique to allow for its potential application in various clinical contexts where conventional FISH assays are currently being utilised.

Identification of CD5/SOX11 double-negative pleomorphic mantle cell lymphoma.

Cyclin D1 protein-positive diffuse large B cell lymphoma (DLBCL) has an immunophenotype of CD5(-) cyclin D1(+) SOX11(-), and most cases lack a CCND1 rearrangement and have a gene expression profile of DLBCL. Rarely, cyclin D1 protein-positive DLBCL harbors a CCND1 rearrangement, and some genetic copy number features typical of mantle cell lymphoma (MCL) have been detected. Since gene expression studies have not been performed, whether such CCND1-rearranged cases represent cyclin D1 protein-positive DLBCL or CD5/SOX11 double-negative pleomorphic MCL remains unclear. To date, no cases of CD5/SOX11 double-negative MCL have been reported. In this study, we collected eight cases initially diagnosed as cyclin D1 protein-positive DLBCL, including four with a CCND1 rearrangement and four without. Immunohistochemically, all four CCND1-rearranged cases had >50% of tumor cells positive for cyclin D1 protein, whereas only one (25%) non-rearranged case had >50% positive tumor cells. Analysis of genome-wide copy number, mutational, and gene expression profiles revealed that CCND1-rearranged cases were similar to MCL, whereas CCND1-non-rearranged cases resembled DLBCL. Despite the SOX11 negativity by immunohistochemistry, CCND1-rearranged cases had a notable trend (P = 0.064) of higher SOX11 mRNA levels compared to non-rearranged cases. Here, we show for the first time that CCND1 rearrangement could be useful for identifying CD5/SOX11 double-negative pleomorphic MCL in cases diagnosed as cyclin D1 protein-positive DLBCL. Cases with >50% cyclin D1 protein-positive tumor cells immunohistochemically and higher SOX11 mRNA levels are more likely to have a CCND1 rearrangement, and fluorescence in situ hybridization can be used to detect the rearrangement.

Nodal Low-Grade B-Cell Lymphoma Co-Expressing CD5 and CD10 but Not CD23, IRTA1, or Cyclin D1: The Diagnostic Challenge of a Splenic Marginal Zone Lymphoma.

The diagnosis of lymphoma is based on histopathological and immunophenotypical features. CD5 and CD10 are traditionally considered a T-cell antigen and a germinal center B-cell antigen, respectively. It is very unusual for a low-grade B-cell lymphoma (BCL) to co-express CD5 and CD10. Although the biologic basis or clinical significance of such co-expression is unclear, this rare event may pose a significant diagnostic challenge. Here, we report a case of a 63-year-old male presenting with bilateral cervical lymphadenopathy and lymphocytosis. Histologically, the nodal tumor was largely diffuse with neoplastic small atypical lymphocytes co-expressing CD5, CD10, and CD20, but not CD23 or cyclin D1. The leukemic cells in the peripheral blood exhibited hairy projections. Taking together the marked splenomegaly, involvement of lymph nodes, bone marrow, and peripheral blood, a final diagnosis of splenic marginal zone lymphoma (SMZL) was reached. The patient was alive with partial response for 10 months after immunochemotherapy. The dual expression of CD5 and CD10 is extremely unusual for low-grade BCL and may lead to an erroneous diagnosis. Integrating the findings into peripheral blood smear tests, flow cytometry, histopathology, imaging, and clinical features is mandatory to exclude other lymphoma types and to reach a correct diagnosis, particularly for a case with nodal presentation.

Spatially-resolved transcriptomics reveal macrophage heterogeneity and prognostic significance in diffuse large B-cell lymphoma.

Macrophages are abundant immune cells in the microenvironment of diffuse large B-cell lymphoma (DLBCL). Macrophage estimation by immunohistochemistry shows varying prognostic significance across studies in DLBCL, and does not provide a comprehensive analysis of macrophage subtypes. Here, using digital spatial profiling with whole transcriptome analysis of CD68+ cells, we characterize macrophages in distinct spatial niches of reactive lymphoid tissues (RLTs) and DLBCL. We reveal transcriptomic differences between macrophages within RLTs (light zone /dark zone, germinal center/ interfollicular), and between disease states (RLTs/ DLBCL), which we then use to generate six spatially-derived macrophage signatures (MacroSigs). We proceed to interrogate these MacroSigs in macrophage and DLBCL single-cell RNA-sequencing datasets, and in gene-expression data from multiple DLBCL cohorts. We show that specific MacroSigs are associated with cell-of-origin subtypes and overall survival in DLBCL. This study provides a spatially-resolved whole-transcriptome atlas of macrophages in reactive and malignant lymphoid tissues, showing biological and clinical significance.

Clinicopathological and genetic landscape of plasmablastic lymphoma in Taiwan.

Plasmablastic lymphoma (PBL) is an aggressive large B-cell lymphoma with a terminal B-cell differentiation phenotype and is frequently associated with immunodeficiency. We aimed to investigate the clinicopathological and immunophenotypic features, genetic alterations, and mutational landscape of PBL in Taiwan. We retrospectively recruited 26 cases. Five (5/18; 28%) patients were HIV-positive and 21 (81%) presented extranodally. There were two morphological groups: one with purely monomorphic large cells (85%) and the other comprising large cells admixed with plasmacytic cells (15%). Phenotypically, the tumors expressed MYC (8/10; 80%), CD138 (20/26; 77%), and MUM1 (20/20; 100%), but not CD20 (n = 26; 0%). Fourteen (54%) cases were positive for EBV by in situ hybridization; the EBV-positive cases were more frequently HIV infected (p = 0.036), with extranodal presentation (p = 0.012) and CD79a expression (p = 0.012), but less frequent light chain restriction (p = 0.029). Using fluorescence in situ hybridization, we identified 13q14 deletion, MYC rearrangement, and CCND1 rearrangement in 74%, 30%, and 5% cases, respectively, without any cases having rearranged BCL6 or IGH::FGFR3 fusion. In the 15 cases with adequate tissue for whole exome sequencing, the most frequent recurrent mutations were STAT3 (40%), NRAS (27%), and KRAS (20%). In conclusion, most PBL cases in Taiwan were HIV-unrelated. Around half of the cases were positive for EBV, with distinct clinicopathological features. Deletion of chromosome 13q14 was frequent. The PBL cases in Taiwan showed recurrent mutations involving JAK-STAT, RAS-MAPK, epigenetic regulation, and NOTCH signaling pathways, findings similar to that from the West.