Interphase cytogenetic analysis of lymphoma-associated chromosomal breakpoints in primary diffuse large B-cell lymphomas of the central nervous system

The Molecular Landscape of Primary CNS Lymphomas (PCNSLs) in Children and Young Adults

Pediatric brain tumors are often noted to be different from their adult counterparts in terms of molecular features. Primary CNS lymphomas (PCNSLs) are mostly found in elderly adults and are uncommon in children and teenagers. There has only been scanty information about the molecular features of PCNSLs at a young age. We examined PCNSLs in 34 young patients aged between 7 and 39 years for gene rearrangements of BCl2, BCL6, CCND1, IRF4, IGH, IGL, IGK, and MYC, homozygous deletions (HD) of CDKN2A, and HLA by FISH. Sequencing was performed using WES, panel target sequencing, or Sanger sequencing due to the small amount of available tissues. The median OS was 97.5 months and longer than that for older patients with PCNSLs. Overall, only 14 instances of gene rearrangement were found (5%), and patients with any gene rearrangement were significantly older (p = 0.029). CDKN2A HD was associated with a shorter OS (p < 0.001). Only 10/31 (32%) showed MYD88 mutations, which were not prognostically significant, and only three of them were L265P mutations. CARD11 mutations were found in 8/24 (33%) cases only. Immunophenotypically, the cases were predominantly GCB, in contrast to older adults (61%). In summary, we showed that molecular findings identified in the PCNSLs of the older patients were only sparingly present in pediatric and young adult patients.

Analysis of the genomic landscape of primary central nervous system lymphoma using whole-genome sequencing in Chinese patients

Primary central nervous system lymphoma (PCNSL) is an uncommon non-Hodgkin's lymphoma with poor prognosis. This study aimed to depict the genetic landscape of Chinese PCNSLs. Whole-genome sequencing was performed on 68 newly diagnosed Chinese PCNSL samples, whose genomic characteristics and clinicopathologic features were also analyzed. Structural variations were identified in all patients with a mean of 349, which did not significantly influence prognosis. Copy loss occurred in all samples, while gains were detected in 77.9% of the samples. The high level of copy number variations was significantly associated with poor progression-free survival (PFS) and overall survival (OS). A total of 263 genes mutated in coding regions were identified, including 6 newly discovered genes (ROBO2, KMT2C, CXCR4, MYOM2, BCLAF1, and NRXN3) detected in ⩾ 10% of the cases. CD79B mutation was significantly associated with lower PFS, TMSB4X mutation and high expression of TMSB4X protein was associated with lower OS. A prognostic risk scoring system was also established for PCNSL, which included Karnofsky performance status and six mutated genes (BRD4, EBF1, BTG1, CCND3, STAG2, and TMSB4X). Collectively, this study comprehensively reveals the genomic landscape of newly diagnosed Chinese PCNSLs, thereby enriching the present understanding of the genetic mechanisms of PCNSL.

Extranodal lymphoma: pathogenesis, diagnosis and treatment

Approximately 30% of lymphomas occur outside the lymph nodes, spleen, or bone marrow, and the incidence of extranodal lymphoma has been rising in the past decade. While traditional chemotherapy and radiation therapy can improve survival outcomes for certain patients, the prognosis for extranodal lymphoma patients remains unsatisfactory. Extranodal lymphomas in different anatomical sites often have distinct cellular origins, pathogenic mechanisms, and clinical manifestations, significantly influencing their diagnosis and treatment. Therefore, it is necessary to provide a comprehensive summary of the pathogenesis, diagnosis, and treatment progress of extranodal lymphoma overall and specifically for different anatomical sites. This review summarizes the current progress in the common key signaling pathways in the development of extranodal lymphomas and intervention therapy. Furthermore, it provides insights into the pathogenesis, diagnosis, and treatment strategies of common extranodal lymphomas, including gastric mucosa-associated lymphoid tissue (MALT) lymphoma, mycosis fungoides (MF), natural killer/T-cell lymphoma (nasal type, NKTCL-NT), and primary central nervous system lymphoma (PCNSL). Additionally, as PCNSL is one of the extranodal lymphomas with the worst prognosis, this review specifically summarizes prognostic indicators and discusses the challenges and opportunities related to its clinical applications. The aim of this review is to assist clinical physicians and researchers in understanding the current status of extranodal lymphomas, enabling them to make informed clinical decisions that contribute to improving patient prognosis.

Lymphomas of Central Nervous System

Central nervous system (CNS) lymphoma consists of primary central nervous system lymphoma (PCNSL) and secondary CNS involvement by systemic lymphoma. This chapter focuses on the former. PCNSL is a relative rare disease, accounting for approximately 2.4-4.9% of all primary CNS tumors. It is an extra-nodal variant of non-Hodgkin's lymphoma (NHL), confined to the brain, leptomeninges, spinal cord, and eyes, with no systemic involvement. Recently, elderly patients (≥ 60 years) are increasing. Histologically, B cell blasts, which originate from late germinal center exit B cell, are growing and homing in CNS. Immunohistochemically, these cells are positive for PAX5, CD19, CD20, CD22, and CD79a. PCNSL shows relatively characteristic appearances on CT, MR imaging, and PET. Treatment first line of PCNSL is HD-MTX-based chemotherapy with or without rituximab and irradiation. Severe side-effect of this treatment is delayed onset neurotoxicity, which cause of cognitive impairment. Therefore, combined chemotherapy alone or chemotherapy with reduced-dose irradiation is more recommended for elderly patients. There is no established standard care for relapse of the PCNSLs. Temsirolimus, lenalidomide, temozolomide, and Bruton's tyrosine kinase (BTK) inhibitor ibrutinib are candidates for refractory patients. The prognosis of PCNSL has significantly improved over the last decades (median OS: 26 months, 5-year survival: 31%). Younger than 60 age and WHO performance status less than < or = 1 are associated with a significantly better overall survival.

Two cases of primary diffuse large B-cell lymphoma of the CNS associated with t(8;14)(q24;q32) or t(3;14)(q27;q32) identified by G-banding and fluorescence in situ hybridization applied to metaphase spreads

We describe two patients with primary diffuse large B-cell lymphoma of the central nervous system (PCNS-DLBCL). The first patient (case 1) was a woman in her late 70s who presented with a tumor in the left frontal lobe, whereas the second patient (case 2) was a man in his early 70s who presented with a left frontal lobe tumor associated with intratumoral hemorrhage. The histopathology of the tumor specimen disclosed the proliferation of large cells with centroblastic (case 1) or immunoblastic/plasmablastic (case 2) cytomorphology and an accumulation of the tumor cells within the perivascular space. The cells in both cases were positive for CD20, CD79a, BCL6, IRF4/MUM1, MYC, and BCL2 and negative for CD5 and CD10. G-banding revealed t(8;14)(q24;q32) in case 1, and the tetraploid-range karyotype including two or three copies of der(3)t(3;14)(q27;q32) and der(14)t(3;14)(q27;q32) in case 2. Fluorescence in situ hybridization applied to metaphase spreads confirmed colocalization of MYC and IGH (case 1) and BCL6 and IGH (case 2) hybridization signals on the relevant derivative chromosomes. Case 1 carried the MYD88^L265P mutation. This case report provides clear evidence for the occurrence of t(8;14)(q24;q32) and t(3;14)(q27;q32) in PCNS-DLBCL using metaphase-based cytogenetic analysis.

The genomic and transcriptional landscape of primary central nervous system lymphoma

Primary lymphomas of the central nervous system (PCNSL) are mainly diffuse large B-cell lymphomas (DLBCLs) confined to the central nervous system (CNS). Molecular drivers of PCNSL have not been fully elucidated. Here, we profile and compare the whole-genome and transcriptome landscape of 51 CNS lymphomas (CNSL) to 39 follicular lymphoma and 36 DLBCL cases outside the CNS. We find recurrent mutations in JAK-STAT, NFkB, and B-cell receptor signaling pathways, including hallmark mutations in MYD88 L265P (67%) and CD79B (63%), and CDKN2A deletions (83%). PCNSLs exhibit significantly more focal deletions of HLA-D (6p21) locus as a potential mechanism of immune evasion. Mutational signatures correlating with DNA replication and mitosis are significantly enriched in PCNSL. TERT gene expression is significantly higher in PCNSL compared to activated B-cell (ABC)-DLBCL. Transcriptome analysis clearly distinguishes PCNSL and systemic DLBCL into distinct molecular subtypes. Epstein-Barr virus (EBV)+ CNSL cases lack recurrent mutational hotspots apart from IG and HLA-DRB loci. We show that PCNSL can be clearly distinguished from DLBCL, having distinct expression profiles, IG expression and translocation patterns, as well as specific combinations of genetic alterations.

Impact of a Faulty Germinal Center Reaction on the Pathogenesis of Primary Diffuse Large B Cell Lymphoma of the Central Nervous System

Simple Summary

The pathogenetic mechanisms and peculiar tropism of primary CNS lymphoma (PCNSL) of the central nervous system (CNS) have been the subject of debate for decades. Hypothesis-driven targeted molecular studies have revealed that PCNSLs derived from self-/polyreactive B cells that have escaped developmental control mechanisms. The early acquisition of activating mutations targeting the B cell receptor pathway provides a survival advantage. The failure of the germinal center (GC) reaction and its checkpoints increases tumor B cell affinity for the CNS. During this faulty GC reaction, PCNSL tumor cells acquire further oncogenic alterations converging on the Toll-like receptor, B cell receptor, and NF-κB pathway. These activated pathways sustain proliferation. Concomitantly, cells become unable to complete terminal B cell differentiation, becoming trapped within the vicious cycle of the GC reaction as low-affinity IgM+ B cells related to memory cells.

Abstract

Primary lymphoma of the central nervous system (PCNSL, CNS) is a specific diffuse large B cell lymphoma (DLBCL) entity confined to the CNS. Key to its pathogenesis is a failure of B cell differentiation and a lack of appropriate control at differentiation stages before entrance and within the germinal center (GC). Self-/polyreactive B cells rescued from apoptosis by MYD88 and/or CD79B mutations accumulate a high load of somatic mutations in their rearranged immunoglobulin (IG) genes, with ongoing somatic hypermutation (SHM). Furthermore, the targeting of oncogenes by aberrant SHM (e.g., PIM1, PAX5, RHOH, MYC, BTG2, KLHL14, SUSD2), translocations of the IG and BCL6 genes, and genomic instability (e.g., gains of 18q21; losses of 9p21, 8q12, 6q21) occur in these cells in the course of their malignant transformation. Activated Toll-like receptor, B cell receptor (BCR), and NF-κB signaling pathways foster lymphoma cell proliferation. Hence, tumor cells are arrested in a late B cell differentiation stage, corresponding to late GC exit B cells, which are genetically related to IgM+ memory cells. Paradoxically, the GC reaction increases self-/polyreactivity, yielding increased tumor BCR reactivity for multiple CNS proteins, which likely contributes to CNS tropism of the lymphoma. The loss of MHC class I antigen expression supports tumor cell immune escape. Thus, specific and unique interactions of the tumor cells with resident CNS cells determine the hallmarks of PCNSL.

PD-L1 and IDO1 are potential targets for treatment in patients with primary diffuse large B-cell lymphoma of the CNS

BACKGROUND

Programmed cell death 1 (PD-1) and its ligands PD-L1 and PD-L2, as well as Indoleamine 2,3-deoxygenase (IDO1) can be expressed both by tumor and microenvironmental cells and are crucial for tumor immune escape. We aimed to evaluate the role of PD-1, its ligands and IDO1 in a cohort of patients with primary diffuse large B-cell lymphoma of the CNS (PCNSL).

MATERIAL AND METHODS

Tissue microarrays (TMAs) were constructed in 45 PCNSL cases. RNA extraction from whole tissue sections and RNA sequencing were successfully performed in 33 cases. Immunohistochemical stainings for PD-1, PD-L1/paired box protein 5 (PAX-5), PD-L2/PAX-5 and IDO1, and Epstein-Barr virus encoding RNA (EBER) in situ hybridization were analyzed.

RESULTS

High proportions of PD-L1 and PD-L2 positive tumor cells were observed in 11% and 9% of cases, respectively. High proportions of PD-L1 and PD-L2 positive leukocytes were observed in 55% and 51% of cases, respectively. RNA sequencing revealed that gene expression of IDO1 was high in patients with high proportion of PD-L1 positive leukocytes (p = .01). Protein expression of IDO1 in leukocytes was detected in 14/45 cases, in 79% of these cases a high proportion of PD-L1 positive leukocytes was observed. Gene expression of IDO1 was high in EBER-positive cases (p = .0009) and protein expression of IDO1 was detected in five of six EBER-positive cases.

CONCLUSION

Our study shows a significant association between gene and protein expression of IDO1 and protein expression of PD-L1 in the tumor microenvironment of PCNSL, possibly of importance for prediction of response to immunotherapies.

Primary Central Nervous System Lymphomas: A Diagnostic Overview of Key Histomorphologic, Immunophenotypic, and Genetic Features

Primary central nervous system lymphoma (PCNSL) is a rare form of extranodal non-Hodgkin lymphoma that primarily arises in the brain, spinal cord, leptomeninges, and vitreoretinal compartment of the eye. The term is sometimes used interchangeably with primary central nervous system diffuse large B-cell lymphoma (PCNS DLBCL) because DLBCL comprises a great majority (90–95%) of PCNSL. Although rare, other types of lymphomas can be seen in the central nervous system (CNS), and familiarity with these entities will help their recognition and further workup in order to establish the diagnosis. The latter is especially important in the case of PCNSL where procurement of diagnostic specimen is often challenging and yields scant tissue. In this review, we will discuss the most common types of primary lymphomas that can be seen in the CNS with emphasis on the diagnostic histomorphologic, immunophenotypic, and molecular genetic features. The differential diagnostic approach to these cases and potential pitfalls will also be discussed.

Molecular features of a large cohort of primary central nervous system lymphoma using tissue microarray

The objective of this study was to evaluate the distribution and prognostic impact of a broad range of molecular attributes in a large cohort of immunocompetent patients with primary central nervous system lymphoma (PCNSL) by using tissue microarray. Patients diagnosed with PCNSL were initially identified in the BC Cancer Lymphoid Cancer clinical and pathology databases. Tissue microarrays were constructed by using archival formalin-fixed paraffin-embedded diagnostic biopsy tissue. Immunohistochemistry and fluorescent in situ hybridization studies were performed. A total of 115 patients with PCNSL with diffuse large B-cell lymphoma (DLBCL) histology were identified. The majority of cases (≥75%) had a non-germinal center B-cell phenotype according to immunohistochemistry algorithms, but cell of origin did not affect progression-free or overall survival. MYC (40%), BCL2 (75%), and programmed death-ligand 1 (29%) protein expression were common, but their corresponding gene rearrangements were rare (≤1% each), suggesting that alternate mechanisms were driving expression. There were no dual rearrangements involving MYC and BCL2. Only 22% of cases had membranous expression of major histocompatibility complex class II, suggesting a mechanism for escape from immune surveillance. Epstein-Barr virus-encoded RNA was positive in 1 immunocompetent patient. BCL6 protein expression (77%) and BCL6 rearrangements (31%) were frequent; the latter was the only factor associated with a poor prognosis in the overall cohort and in the subgroup of 52 patients treated with high-dose methotrexate-based regimens. This large population-based study shows that prominent molecular features of PCNSL are unique and different from those of systemic DLBCL. These results may better inform drug development in PCNSL.

Analysis of primary central nervous system large B-cell lymphoma in the era of high-grade B-cell lymphoma: Detection of two cases with MYC and BCL6 rearrangements in a cohort of 12 cases

High-grade diffuse large B-cell lymphoma (HG-DLBCL) refers to DLBCL with MYC and BCL2 and/or BCL6 rearrangements (double-hit or triple-hit DLBCL) that exhibits poor prognosis. Double-expressor DLBCL (c-myc+/bcl-2+) has intermediate prognosis when compared to HG-DLBCL. Primary central nervous system lymphoma (PCNSL) has distinct pathophysiology (frequent non-germinal center-like subtype and double-expressor) and has worse prognosis than systemic DLBCL. By fluorescence in situ hybridization (FISH), 25-30% of PCNSLs harbor BCL6 abnormalities with rare alterations in MYC, BCL2, double-hit or triple-hit events. We describe the clinicopathologic features and status of MYC, BCL2 and BCL6 in 12 PCNSLs (7 women, 5 men; median age 63 years; range: 28-79). Six cases showed focal starry-sky pattern. Immunohistochemically, all (100%) were of non-germinal center-like subtype, and 8/10 (80%) cases were double-expressors. Ki-67 ranged from 70 to 100%. FISH was positive in 9/12 (75%) cases: 4 (33%) harbored a BCL6 rearrangement, 3 (25%) had a gain of BCL2, 2 (17%) cases each had a gain of BCL6 and gain of IGH, and gain of MYC and deletion of MYC were observed in 1 case each (8%). Two (16%) cases were MYC/BCL6 double-hit PCNSLs. No MYC/BCL2 or triple-hit cases were identified. Eleven (92%) patients received chemotherapy and one also received whole brain radiation. The median time of follow-up was 4.4 months (range, 0.3-40.3). Seven (58%) patients are alive, 4 (33%) have died, and 1 (8%) had no follow-up. Five alive patients are in remission, including one MYC/BCL6 double-hit PCNSL. Our results add two new cases of rare double-hit PCNSL to the literature.

Molecular Diagnostics in Lymphoid Neoplasms of the Central Nervous System

Primary lymphoid neoplasms of the central nervous system are rare tumors that span a wide range of histopathologic appearances and can overlap occasionally with non-neoplastic processes. Application of modern molecular techniques has not only begun to unravel their unique underlying biology but has also started to lay a valuable diagnostic and therapeutic framework for these frequently aggressive malignancies. This review summarizes the existing landscape of clinicopathologic and genomic features of lymphoid neoplasms that may arise primarily within the central nervous system.

Rare cases of primary central nervous system anaplastic variant of diffuse large B-cell lymphoma

BACKGROUND

Primary central nervous system (CNS) diffuse large B-cell lymphoma (DLBCL) is a rare intracranial tumor, defined as DLBCL arising from the brain, spinal cord, leptomeninges and eye, with an overall annual incidence of 5 cases per million. The primary CNS anaplastic variant of DLBCL (A-DLBCL) is even less common; to our knowledge, there are only two other case reports in the literature. The aim of this report is to present rare cases of primary CNS A-DLBCL and study their clinicopathologic and genetic features.

CASE PRESENTATION

We report 3 patients, two men and one woman, aged 54, 55 and 67 years old, with primary CNS A-DLBCL. All 3 patients had a high International Extranodal Lymphoma Study Group (IELSG) score; although the patients were treated with methotrexate-based regimens and/or with radiation therapy, the overall survival was only 2, 5, and 8 months. All 3 patients presented with characteristic features of perivascular space infiltration with bizarre-shaped tumor cells, leading to the diagnosis of primary CNS A-DLBCL. Concurrent of MYC and BCL2 and/or BCL6 abnormalities and MYC/BCL2 double-expressor DLBCL occurred in all 3 patients; two patients had MYC/BCL2/BCL6 triple extra copies, and one patient had MYC extra copy and BCL6 translocation. All 3 patients displayed mutations in MYD88 L265P and nuclear positivity for RELA, RELB and/or c-Rel, indicating constitutive activation of the NF-κB pathway.

CONCLUSIONS

These cases shed light on the unique genetic alterations and biological features of primary CNS A-DLBCL. Patients with primary CNS A-DLBCL may often have a MYC/BCL2 double-expressor and concurrent MYC and BCL2 and/or BCL6 genetic abnormalities, as well as constitutive activation of the NF-κB pathway. Primary CNS A-DLBCL follows a very aggressive disease course and poor prognosis. In the future, a large number of cases should be analyzed, and the evaluation of molecular genetic characteristics could help with practical and therapeutic implications for primary CNS A-DLBCL.

Primary vitreoretinal lymphoma

Primary vitreoretinal lymphoma (PVRL) is a rare ocular lymphoid malignancy, which consists a subset of primary central system lymphoma (PCNSL) and the most common type of intraocular lymphoma. The involvement of eyes is estimated to be approximately 20% of PCNSL, but the brain involvement may be up to 80% of PVRL. Typically, PVRL is a high grade B-cell malignancy of the retina and needs to be assorted from choroidal low-grade B-cell lymphomas. Very often PVRL masquerades and can be erroneously diagnosed as chronic uveitis, white dot syndromes or other neoplasms. Establishing an accurate diagnosis may involve cytology/pathology, immunohistochemistry, flow cytometry, molecular pathology and cytokine profile analysis. There is inadequate information about PVRL’s true incidence, ethnic/geographical variation and pathogenetic mechanisms. The therapeutic approach of PVRL involves aggressive chemotherapy and radiation therapy. Although PVRL tends to have a good response to the initial treatment, the prognosis is poor and the survival restricted due to the high relapse rates and CNS involvement.

MYC, BCL2, and BCL6 rearrangements in primary central nervous system lymphoma of large B cell type

Primary central nervous system lymphoma (PCNSL) is a rare specific subtype of non-Hodgkin lymphoma limited to the brain, leptomeninges, spinal cord, or eyes without any systemic presentation and relapse which mostly takes place in CNS. In more than 95% of patients, it is of diffuse large B cell lymphoma (DLBCL) type. Categorizing PCNSL to germinal center cell like or activated B cell like, as we usually do for DLBCL NOS, may not be applicable for predicting outcome. Possible prognostic significance of MYC, BCL2, and/or BCL6 rearrangements may be important given what we know about their impact in systemic DLBCL, but we have limited knowledge about the status of double or triple hit molecular changes in PCNSL. Here, we have investigated prevalence of these molecular alterations in PCNSL. Two independent tissue microarrays constructed from 78 formalin-fixed paraffin-embedded blocks of confirmed PCNSL were tested for rearrangement of MYC, BCL2, and BCL6 by interphase fluorescent in situ hybridization (FISH) using break apart dual color probes. BCL6 translocation was detected in 15 (12%) cases. Translocation involving MYC and BCL2 was identified in 3 cases (3.8%) and 1 case (1.3%) respectively. One double hit lymphoma was discovered with both MYC/BCL2 translocation (1.3%). To the best of our knowledge, few organized studies have been conducted for MYC, BCL2, and/or BCL6 rearrangement in PCNSL. This study is evaluating large number of PCNSL. Double or triple hit events which are rarely seen in PCNSL.

Characterization of genomic alterations in primary central nervous system lymphomas

PURPOSE

Primary central nervous system lymphoma (PCNSL) is a non-Hodgkin lymphoma that affects the central nervous system (CNS). Although previous studies have reported the most common mutated genes in PCNSL, including MYD88 and CD79b, our understanding of genetic characterizations in primary CNS lymphomas is limited. The aim of this study was to perform a retrospective analysis investigating the most frequent mutation types, and their frequency, in PCNSL.

METHODS

Fifteen patients with a diagnosis of PCNSL from our institution were analyzed for mutations in 406 genes and rearrangements in 31 genes by next generation sequencing (NGS).

RESULTS

Missense mutations were identified as the most common mutation type (32%) followed by frame shift mutations (23%). The highest mutation rate was reported in the MYD88 (33.3%), CDKN2A/B (33.3%), and TP53 (26.7%) genes. Intermediate tumor mutation burden (TMB) and high TMB was detected in 13.3% and 26.7% of PCNSL, respectively. The most frequent gene rearrangement involved the IGH-BCL6 genes (20%).

CONCLUSIONS

This study shows the most common genetic alterations in PCNSL as determined by a commercial next generation sequencing assay. MYD88 and CD79b are frequently mutated in PCNSL, IGH-BCL6 is the most frequent gene rearrangement and approximately 1/4 of cases show a high TMB. Mutations in multiple genes, in addition to high TMB and gene rearrangements, highlights the complex molecular heterogeneity of PCNSL. Knowledge about genetic alterations in PCNSL can inform the development of novel targets for diagnosis and treatment.

Primary extranodal diffuse large B-cell lymphomas: Many sites, many entities? Clinico-pathological, immunohistochemical and cytogenetic study of 106 cases

We analyzed the clinicopathological, immunohistochemical and cytogenetic features of 106 extranodal (EN) diffuse large B-cell lymphomas (DLBCLs) from stomach (34 cases), intestine (10), cervico-cephalic region (11), central nervous system (13), testes (21), skin (8), and miscellaneous sites (9). Hans' algorithm and the immunohistochemical double expressor score (DES) for MYC and BCL2 were applied to all cases. A subset of fifty-eight cases were analyzed with fluorescent in situ hybridization (FISH) with specific break apart probes for BCL6, MYC, BCL2, CCND1, BCL10 and MALT1 genes. Clinical records were available for all patients. The immunohistochemical study showed that, in our series of EN-DLBCLs, the Hans' subgroup and the DES differed significantly according to the site of origin. At FISH analysis, BCL6 and BCL2 were the most commonly rearranged genes in non-GC and in GC cases, respectively. Gastrointestinal lymphomas displayed the highest rate of gene rearrangements, often with MYC involvement. One testicular DLBCL showed BCL2/MYC double hit. At survival analysis, cerebral and testicular origin was associated with poor prognosis. In addition, Hans' subgroup and other immunohistochemical markers influenced patients' outcome. In conclusion, our data suggest that immunophenotypic, genetic and survival characteristics of EN-DLBCL are related to the specific primary site of the disease.

Target amplicon exome-sequencing identifies promising diagnosis and prognostic markers involved in RTK-RAS and PI3K-AKT signaling as central oncopathways in primary central nervous system lymphoma

Exome-sequencing for somatic mutation detection and copy number variation analysis are effective and valid methods for evaluating human cancers in current molecular medicine. We conducted target amplicon exome-sequencing analyses using PCR target enrichment and next-generation sequencing on Ion Proton semiconductor sequencers. Twenty-seven primary central nervous system lymphoma (PCNSL) specimens and their corresponding noncancerous tissues were used for multiplex PCR amplification to obtain targeted coverages of the entire coding regions of 409 cancer-related genes. The average of the total numbers of somatic mutations including single-nucleotide variations and insertion/deletion mutations in each specimen was 13.3. Of these, the average of the ratios of nonsynonymous substitutions in each specimen was 74.8%. The most frequent mutations in 27 specimens were in PIM1, MYD88, CD79B, DST, IRF4, ERBB3, MYH11, DCC, and KMT2D. Furthermore, somatic mutations of MYH11 were related to poor prognoses in PCNSL patients. Copy number variations were also duplicated and/or deleted from deep-sequencing in segmental genomic islands. In addition to these prognostic marker candidates, analysis of RTK-RAS-MAPK signaling and the PTEN-PI3K-AKT proapoptotic pathway showed that somatic activations and aberrations, respectively, may be involved in a promising central oncopathway harboring mTOR, c-Myc, FOXO1, and p53. This study provides a foundation for molecular targeted therapies based on genome diagnostics and prognosis in PCNSL.

Neural Tumors of the Orbit -- What Is New?

Primary neural tumors of the orbit account for approximately 10% of all orbital tumors. Different tumor entities include meningiomas, optic nerve gliomas, neurofibromas, schwannomas, malignant peripheral nerve sheath tumors, and granular cell tumors. This review summarizes current concepts regarding epidemiology, clinical presentation, diagnosis, pathology, immunohistochemistry, prognosis, and treatment for neural tumors of the orbit based on the available literature.

Primary Vitreoretinal Lymphoma -- A Review

Primary vitreoretinal lymphoma (PVRL) is the most common intraocular lymphoma occurring in the eye. It is a high-grade typically B-cell malignancy, arising in the retina, and is often associated with central nervous system (CNS) disease and thereby a poor prognosis. It needs to be distinguished from choroidal low-grade B-cell lymphomas, which do not disseminate to the brain and have a good prognosis. Because of the rarity of PVRL, information is lacking regarding its true incidence, its geographical or ethnic variation, and underlying risk factors apart from immunosuppression associated with human immunodeficiency virus (HIV) and Epstein Barr virus. PVRL often presents masquerading as other intraocular diseases and is therefore often associated with diagnostic delays. This is compounded by the fragility of the neoplastic B cells, which hampers vitrectomy yields and pathological work-up. The latter includes cytomorphology and immunoprofiling, with adjunctive tests such as cytokine analysis, polymerase chain reaction for clonality, MYD88 mutational testing, and possibly bespoke next generation sequencing. Recent examinations of PVRL and CNS lymphoma (CNSL) using whole genome sequencing confirm that these tumors arise from activated postgerminal center cells, reflecting their aggressive course in most cases. The treatment of PVRL varies between centers and is dependent on presence or absence of concomitant CNS disease. The prognosis remains poor, and yet progress is steadily being made through international collaborative clinical trials.

Primary central nervous system lymphoma: essential points in diagnosis and management

Primary central nervous system lymphoma (PCNSL) is an extra-nodal non-Hodgkin lymphoma. PCNSL is defined as lymphoma involving the brain, leptomeninges, eyes, or spinal cord without evidence of lymphoma outside the CNS. Treatment includes induction with chemotherapy and consolidation with whole-brain radiotherapy or high-dose chemotherapy supported by autologous stem cell transplantation. High-dose methotrexate is the most important drug in cases with PCNSL, and this drug will be used in combination with small molecules, BTK inhibitors, new monoclonal antibodies, and checkpoint blockers.

PD1 and PDL1 expression in primary central nervous system diffuse large B-cell lymphoma are frequent and expression of PD1 predicts poor survival

Primary central nervous system diffuse large B-cell lymphoma (PCNS-DLBCL) is a rare and aggressive type of diffuse large B-cell lymphoma (DLBCL) whit poorly understood pathogenesis. Finding biomarkers associated with patient survival may be important for understanding its physiopathology and to develop new therapeutic approaches. We investigated 32 PCNS-DLBCL from immunocompetent patients for BCL2, CMYC, LMO2, and P53 expression and for cytogenetic aberrations of BCL2, BCL6, and MYC genes, all known for their prognostic value in systemic DLBCL (s-DLBCL). We analyzed PD1 and PDL1 protein expression in both tumor infiltrating lymphocytes (TILs) and tumor cells. Finally, we searched for correlation between biological data and clinical course. The PCNS-DLBCL expressed BCL2, CMYC, LMO2, and P53 at similar frequency than s-DLBCL but without significant prognostic on survival. None cases harbored aberrations involving BCL2 and MYC gene whereas BCL6 abnormalities were present in 20.7% of cases but without value on survival. Expression of PD1 in TILs and PDL1 in tumor cells was observed at higher rates than in s-DLBCL (58% and 37%, respectively). The PD1 expression in TILs correlated with PDL1 expression in tumor cells (P = .001). Presence of PD1 positive TILs was associated with poorer overall survival (P = .011). Patients with PDL1 overexpression tended to better response to chemotherapy (P = .23). In conclusion PCNS-DLBCL pathogenesis differs from s-DLBCL without prognostic value of the phenotypic and cytogenetic parameters known for their pejorative impact in the latter. The PD1/PDL1 pathway plays a strong role in PCNS-DLBCL and represents an attractive target for this aggressive lymphoma.

How we diagnose and treat vitreoretinal lymphoma

The eye is a rare site for the development of malignant lymphoma. Based on cell type and involved intraocular structures, which as a whole represent an immune-privileged site, several subtypes of primary intraocular lymphoma need to be discerned. Primary vitreoretinal lymphoma (PVRL), the most common form, is an aggressive B-cell malignancy and considered a subtype of primary central nervous system (CNS) lymphoma. Ocular symptoms are non-specific and often mimic uveitis, frequently resulting in delayed diagnosis. Bilateral ocular involvement and dissemination/relapse in the CNS are common. Diagnosis of PVRL is usually based on the analysis of vitreous biopsy material. In addition to cytological and immunocytochemical examination, measurements of cytokine levels and molecular determination of B-cell clonality and recurrent mutations increase the diagnostic yield. Both systemic chemotherapy and exclusively local treatment, including ocular radiotherapy and intravitreal chemotherapy, are successful approaches for the management of PVRL, although it is currently not predictable which patients require systemic treatment in order to avoid cerebral dissemination, a complication associated with a considerably worse prognosis.

MYC protein expression is associated with poor prognosis in primary diffuse large B-cell lymphoma of the central nervous system

MYC and BCL2 gene translocations and protein expression have recently demonstrated to be of prognostic significance in systemic diffuse large B-cell lymphoma (DLBCL). However, their role in primary central nervous system DLBCL (CNS-DLBCL) prognosis has been scarcely analyzed. We studied the immunophenotype, the status of the MYC, BCL2, and BCL6 genes and the clinical features of a series of 42 CNS-DLBCL and evaluated their prognostic significance. We found high MYC protein expression in 43% of cases, and this was associated with lower overall survival (OS). Cases with concurrent expression of MYC and BCL2 showed a lower OS, although the difference did not reach statistical significance. Translocations involving the MYC or BCL2 genes were not detected. The BCL6 gene was frequently translocated, but was unrelated to survival. We conclude that MYC protein expression detected by immunohistochemistry identifies a CNS-DLBCL subset with worse prognosis and may contribute to a more accurate risk stratification of CNS-DLBCL patients.

Genome-Wide Analysis Uncovers Novel Recurrent Alterations in Primary Central Nervous System Lymphomas

PURPOSE

Primary central nervous system lymphoma (PCNSL) is an aggressive non-Hodgkin lymphoma confined to the central nervous system. Whether there is a PCNSL-specific genomic signature and, if so, how it differs from systemic diffuse large B-cell lymphoma (DLBCL) is uncertain.

EXPERIMENTAL DESIGN

We performed a comprehensive genomic study of tumor samples from 19 immunocompetent PCNSL patients. Testing comprised array-comparative genomic hybridization and whole exome sequencing.

RESULTS

Biallelic inactivation of TOX and PRKCD was recurrently found in PCNSL but not in systemic DLBCL, suggesting a specific role in PCNSL pathogenesis. In addition, we found a high prevalence of MYD88 mutations (79%) and CDKN2A biallelic loss (60%). Several genes recurrently affected in PCNSL were common with systemic DLBCL, including loss of TNFAIP3, PRDM1, GNA13, TMEM30A, TBL1XR1, B2M, CD58, activating mutations of CD79B, CARD11, and translocations IgH-BCL6. Overall, B-cell receptor/Toll-like receptor/NF-κB pathways were altered in >90% of PNCSL, highlighting its value for targeted therapeutic approaches. Furthermore, integrated analysis showed enrichment of pathways associated with immune response, proliferation, apoptosis, and lymphocyte differentiation.

CONCLUSIONS

In summary, genome-wide analysis uncovered novel recurrent alterations, including TOX and PRKCD, helping to differentiate PCNSL from systemic DLBCL and related lymphomas.

The mutational pattern of primary lymphoma of the central nervous system determined by whole-exome sequencing

To decipher the mutational pattern of primary CNS lymphoma (PCNSL), we performed whole-exome sequencing to a median coverage of 103 × followed by mutation verification in 9 PCNSL and validation using Sanger sequencing in 22 PCNSL. We identified a median of 202 (range: 139-251) potentially somatic single nucleotide variants (SNV) and 14 small indels (range: 7-22) with potentially protein-changing features per PCNSL. Mutations affected the B-cell receptor, toll-like receptor, and NF-κB and genes involved in chromatin structure and modifications, cell-cycle regulation, and immune recognition. A median of 22.2% (range: 20.0-24.7%) of somatic SNVs in 9 PCNSL overlaps with the RGYW motif targeted by somatic hypermutation (SHM); a median of 7.9% (range: 6.2-12.6%) affects its hotspot position suggesting a major impact of SHM on PCNSL pathogenesis. In addition to the well-known targets of aberrant SHM (aSHM) (PIM1), our data suggest new targets of aSHM (KLHL14, OSBPL10, and SUSD2). Among the four most frequently mutated genes was ODZ4 showing protein-changing mutations in 4/9 PCNSL. Together with mutations affecting CSMD2, CSMD3, and PTPRD, these findings may suggest that alterations in genes having a role in CNS development may facilitate diffuse large B-cell lymphoma manifestation in the CNS. This may point to intriguing mechanisms of CNS tropism in PCNSL.

Systems biology of primary CNS lymphoma: from genetic aberrations to modeling in mice

Primary lymphoma of the central nervous system (CNS, PCNSL) is a specific diffuse large B cell lymphoma entity arising in and confined to the CNS. Despite extensive research since many decades, the pathogenetic mechanisms underlying the remarkable tropism of this peculiar malignant hematopoietic tumor remain still to be elucidated. In the present review, we summarize the present knowledge on the genotypic and phenotypic characteristics of the tumor cells of PCNSL, give an overview over deregulated molecular pathways in PCNSL and present recent progress in the field of preclinical modeling of PCNSL in mice. With regard to the phenotype, PCNSL cells resemble late germinal center exit IgM+IgD+ B cells with blocked terminal B cell differentiation. They show continued BCL6 activity in line with ongoing activity of the germinal center program. This together with the pathways deregulated by genetic alterations may foster B cell activation and brisk proliferation, which correlated with the simultaneous MYC and BCL2 overexpression characteristic for PCNSL. On the genetic level, PCNSL are characterized by ongoing aberrant somatic hypermutation that, besides the IG locus, targets the PAX5, TTF, MYC, and PIM1 genes. Moreover, PCNSL cells show impaired IG class switch due to sμ region deletions, and PRDM1 mutations. Several important pathways, i.e., the B cell receptor (BCR), the toll-like receptor, and the nuclear factor-κB pathway, are activated frequently due to genetic changes affecting genes like CD79B, SHIP, CBL, BLNK, CARD11, MALT1, BCL2, and MYD88. These changes likely foster tumor cell survival. Nevertheless, many of these features are also present in subsets of systemic DLBLC and might not be the only reasons for the peculiar tropism of PCNSL. Here, preclinical animal models that closely mimic the clinical course and neuropathology of human PCNSL may provide further insight and we discuss recent advances in this field. Such models enable us to understand the pathogenetic interaction between the malignant B cells, resident cell populations of the CNS, and the associated inflammatory infiltrate. Indeed, the immunophenotype of the CNS as well as tumor cell characteristics and intracerebral interactions may create a micromilieu particularly conducive to PCNSL that may foster aggressiveness of tumor cells and accelerate the fatal course of disease. Suitable animal models may also serve as a well-defined preclinical system and may provide a useful tool for developing new specific therapeutic strategies.

Chromosome abnormalities in diffuse large B-cell lymphomas: analysis of 231 Chinese patients

Genome instability is a hallmark of cancer. Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin lymphoma with high levels of chromosomal aberrations. The purpose of this study was to characterize chromosomal aberrations in Chinese DLBCL patients and to compare chromosomal abnormalities between germinal centre B-cell-like (GCB) and non-GCB subgroups. Fluorescence in situ hybridization, G-band cytogenetics and immunohistochemistry were performed in 231 cases of de novo DLBCL. We demonstrated that the rate of abnormal and complex karyotypes was 89.1% (139/156) and 92.8% (129/139), respectively. We found a total of 490 structural chromosomal aberrations, including 96 frequent and recurring structural alterations. Most importantly, we identified several rare or novel chromosomal alterations: eight gains (5, 13, 14q, 17, 19p, 20, 21p, Y), one loss (21) and three recurrent translocations [t(7;15)(q22;q22), t(3;20)(p24;q13.1), t(2;3)(q21;q25)]. Moreover, the frequent recurrent genomic imbalance between GCB and non-GCB subgroups was different. Finally, we discovered two cases of concurrent IGH-BCL6 and MYC rearrangements. The rate of abnormal karyotypes in DLBCL patients of Chinese descent was similar to that of Western countries, but some common karyotypes were different, as were the abnormal karyotypes of GCB and non-GCB subgroups. Our discovery of rare and novel abnormal karyotypes may represent unique chromosomal alterations in Chinese DLBCL patients.

Modern concepts in the biology, diagnosis, differential diagnosis and treatment of primary central nervous system lymphoma

Recent studies addressing the molecular characteristics of PCNSL, which is defined as malignant B-cell lymphoma with morphological features of DLBCL, have significantly improved our understanding of the pathogenesis of this lymphoma entity, which is associated with an inferior prognosis as compared with DLBCL outside the CNS. This unfavorable prognosis stimulated intense efforts to improve therapy and induced recent series of clinical studies, which addressed the role of radiotherapy and various chemotherapeutic regimens. This review combines the discussion of diagnosis, differential diagnosis and recent progress in studies addressing the molecular pathogenesis as well as therapeutic options in PCNSL.

How I treat primary CNS lymphoma

Primary CNS lymphoma (PCNSL) is a rare malignancy with peculiar clinical and biologic features, aggressive course, and unsatisfactory outcome. It represents a challenge for multidisciplinary clinicians and scientists as therapeutic progress is inhibited by several issues. Molecular and biologic knowledge is incomplete, limiting the identification of new therapeutic targets, and the particular microenvironment of this malignancy, and sanctuary sites where tumor cells grow undisturbed, strongly affects treatment efficacy. Moreover, active treatments are known to be associated with disabling neurotoxicity, posing the dilemma of whether to intensify therapy to improve the cure rate or to de-escalate treatment to avoid sequels. The execution of prospective trials is also difficult because of the rarity of the tumor and the impaired general condition and poor performance status of patients. Thus, level of evidence is low, with consequent uncertainties in therapeutic decisions and lack of consensus on primary endpoints for future trials. Despite this unfavorable background, laboratory and clinical researchers are coordinating efforts to develop new ideas, resulting in the recent publication of studies on PCNSL's biology and molecular mechanisms and of the first international randomized trials. Herein, these important contributions are analyzed to provide recommendations for everyday practice and the rationale for future trials.

Primary central nervous system lymphoma: a clinicopathological study of 75 cases

AIMS

Pathological and clinical data in a large series of immunocompetent patients with primary lymphoma of the central nervous system (PCNSL) were analysed.

METHODS

We immunostained tumour specimens of 75 patients for CD3, CD4, CD5, CD8, CD10, CD20, CD30, CD79a, Bcl-2, Bcl-6, CD138, MUM1, TDT, PAX5, FOXP1 and Ki-67 and performed in situ hybridisation for Epstein-Barr virus (EBV) RNA. Eleven cases were investigated for rearrangements of BCL6, immunoglobulin heavy chain (IGH) and FOXP1 genes using fluorescent in situ hybridisation (FISH).

RESULTS

Histologically, most cases were classified as diffuse large B-cell lymphoma (80.2%) predominantly of centroblastic type. Immunophenotypic profiling revealed that 96% and 4% of cases corresponded to non-germinal centre and germinal centre type, respectively. FISH analysis showed t(3;14)/IGH-BCL6 in 2/11 cases and trisomy 3 in 2/11 cases. FOXP1 rearrangements were not found. At survival analysis, Karnofsky index >80 and presence of Bcl-6 expression showed independent significant association with favourable patient outcome.

CONCLUSIONS

PCNSL represents a histologically and immunophenotypically very homogeneous lymphoma type, probably derived from germinal centre exit B cells. The frequent overexpression of FOXP1 appears not to be related to FOXP1 gene rearrangement. Survival analyses disclosed Bcl-6 expression and high Karnofsky performance score as independent prognostic parameters associated with favourable outcome.

Mutations of CARD11 but not TNFAIP3 may activate the NF-kappaB pathway in primary CNS lymphoma

Primary CNS lymphoma (PCNSL), the intracerebral subgroup of diffuse large B cell lymphoma (DLBCL), shows evidence for aberrant activation of the nuclear factor (NF)-kappaB pathway. In order to identify potential activators of the NF-kappaB complex, we analyzed the CARD11 and TNFAIP3 genes for the presence of somatic mutations and TNFAIP3 for aberrant promoter methylation in PCNSL. We also compared PCNSL to spinal DLBCL, because CARD11 and TNFAIP3 mutations have been described in systemic DLBCL. CARD11 mutations, located in the coiled-coil region, which may activate NF-kappaB, were detected in 16% (5/32) of PCNSL, while TNFAIP3 mutations were detected in 3% (1/32) of PCNSL. In PCNSL, all CARD11 mutations were heterozygous, in-frame, induced amino acid exchanges, and presumably led to activation of this oncogene. Spinal DLBCL harbored mutations of CARD11 and TNFAIP3 in 10% (1/10) and 20% (2/10) of cases, respectively. In both PCNSL and spinal DLBCL, mutations in CARD11 and TNFAIP3 were mutually exclusive. TNFAIP3 was unmethylated in all PCNSLs (30/30) and spinal DLBCLs (10/10). We conclude that mutations of the oncogene CARD11 may contribute to NF-kappaB activation and thereby play a role in the pathogenesis of PCNSL, while, in contrast to systemic DLBCL, inactivation of TNFAIP3 either by mutation or methylation seems to be of minor significance.

Chromosomal imbalances and partial uniparental disomies in primary central nervous system lymphoma

To determine the pattern of genetic alterations in primary central nervous system lymphomas (PCNSL), 19 PCNSL were studied by high-density single-nucleotide polymorphism arrays. Recurrent losses involved 6p21.32, 6q21, 8q12-12.2, 9p21.3, 3p14.2, 4q35.2, 10q23.21 and 12p13.2, whereas gains involved 18q21-23, 19q13.31, 19q13.43 and the entire chromosomes X and 12. Partial uniparental disomies (pUPDs) were identified in 6p and 9p21.3. These genomic alterations affected the HLA locus, the CDKN2A/p16, CDKN2B/p15 and MTAP, as well as the PRDM1, FAS, MALT1, and BCL2 genes. Increased methylation values of the CDKN2A/p16 promoter region were detected in 75% (6/8) PCNSL. Gene expression profiling showed 4/21 (20%) minimal common regions of imbalances to be associated with a differential mRNA expression affecting the FAS, STAT6, CD27, ARHGEF6 and SEPT6 genes. Collectively, this study unraveled novel genomic imbalances and pUPD with a high resolution in PCNSL and identified target genes of potential relevance in the pathogenesis of this lymphoma entity.

Insights into the biology of primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is a rare variant of non-Hodgkin lymphoma that is confined to the central nervous system. Biologic studies of PCNSL are challenging to conduct because the disease is rare and available tissue material is sparse. However, in recent years there has been progress in the understanding of PCNSL biology, largely as the result of multicenter studies using modern molecular techniques. Recent studies may improve insight into the pathogenesis of PCNSL and increase the chances of identifying prognostic factors and novel therapeutic targets. This review discusses recent advances in PCNSL biology, including immunologic and genetic risk factors, and focuses on the molecular alterations important in central nervous system lymphomagenesis.

Recurrent inactivation of the PRDM1 gene in primary central nervous system lymphoma

Primary lymphomas of the CNS (PCNSLs) show molecular features of the late germinal center exit B-cell phenotype and are impaired in their terminal differentiation as indicated by a lack of immunoglobulin class switching. Because the positive regulatory domain I protein with ZNF domain (PRDM1/BLIMP1) is a master regulator of terminal B-cell differentiation into plasma cells, we investigated a series of 21 PCNSLs for the presence of mutations in the PRDM1 gene and alterations in the expression pattern of the PRDM1 protein. Direct sequencing of all coding exons of the PRDM1 gene identified deleterious mutations associated with abrogation of PRDM1 protein expression in 4 of 21 (19%) PCNSLs. Thus, similar to systemic diffuse large B-cell lymphomas, PRDM1 may be a tumor suppressor in some PCNSL and contribute to lymphomagenesis by impairing terminal differentiation.

Modified IDARAM chemotherapy regimen for primary central nervous system lymphoma: experience of three cases

The use of radiotherapy (RT) with chemotherapy has improved disease free survival and control in primary central nervous system lymphoma (PCNSL). We have encountered three patients with histologically documented central nervous system lymphoma. In all patients pathological diagnosis was B-cell lymphoma. We modified IDARAM regimen to R-IDARAM to enhance and optimize chemotherapeutic components for the treatment of PCNSL. We made three changes: (i) we added rituximab 375 mg/m(2) day 1; (ii) increased dose of MTX from 2 to 3 g/m(2); and (iii) administered two additional courses of R-IDARAM after cranial RT. Following complete staging after course 2, radiotherapy was applied at a dosage of 3600-4140 cGy in conventional schedule (180 or 200 cGy per day) to whole brain (with 3600 cGy to eyes in one case because of eye involvement) and then 2 additional courses of R-IDARAM (totally four courses) chemotherapy regimen were applied. Complete remission (CR) was achieved after first two cycles of R-IDARAM in patient 1 and 3 and after four cycles in patient 2. Currently, three patients have been alive for 29, 10, 15 months respectively. Currently there is no standard treatment modality for PCNSL. Increased dosage of MTX, adding rituximab and consolidation of the IDARAM to R-IDARAM regimen may improve disease control and outcome in PCNSL patients.

Del(6)(q22) and BCL6 rearrangements in primary CNS lymphoma are indicators of an aggressive clinical course

PURPOSE

Primary CNS lymphoma (PCNSL) is an aggressive lymphoma but clinically validated biologic markers that can predict natural history to tailor treatment according to risk are lacking. Several genetic changes including BCL6 rearrangements and deletion of 6q22, containing the putative tumor suppressor gene PTPRK, are potential risk predictors. Herein we determined the prevalence and survival impact of del(6)(q22) and BCL6, immunoglobulin heavy chain (IGH), and MYC gene rearrangements in a large PCNSL cohort treated in a single center.

PATIENTS AND METHODS

Interphase fluorescence in situ hybridization was performed using two-color probes for BCL6, MYC, IGH-BCL6, and del(6)(q22) on thin sections of 75 paraffin-embedded samples from 75 HIV-negative, immunocompetent patients newly diagnosed with PCNSL. Survival data were analyzed using Kaplan-Meier survival curves, log-rank tests, and proportional hazards regression adjusting for age, deep structure involvement, and high-dose methotrexate (HDMTX) treatment.

RESULTS

The prevalence of del(6)(q22) and BCL6, IGH, and MYC translocations was 45%,17%, 13%, and 3%, respectively. The presence of del(6)(q22) and/or a BCL6 translocation was associated with inferior overall survival (OS; P = .0097). The presence of either del(6)(q22) alone or a BCL6 translocation alone was also associated with inferior OS (P = .0087). Univariable results held after adjusting for age, deep structure involvement, and HDMTX.

CONCLUSION

Del (6)(q22) and BCL6 rearrangements are common in PCNSL and predict for decreased OS independent of deep structure involvement and HDMTX. Unlike systemic diffuse large B-cell lymphoma, del(6)(q22) is common and IGH translocations are infrequent and usually involve BCL6 rather than BCL2, suggesting a distinct pathogenesis.

Gene expression profiling suggests primary central nervous system lymphomas to be derived from a late germinal center B cell

To characterize the molecular origin of primary lymphomas of the central nervous system (PCNSL), 21 PCNSLs of immunocompetent patients were investigated by microarray-based gene expression profiling. Comparison of the transcriptional profile of PCNSL with various normal and neoplastic B-cell subsets demonstrated PCNSL (i) to display gene expression patterns most closely related to late germinal center B cells, (ii) to display a gene expression profile similar to systemic diffuse large B-cell lymphomas (DLBCLs) and (iii) to be in part assigned to the activated B-cell-like (ABC) or the germinal center B-cell-like (GCB) subtype of DLBCL.

Primary testicular diffuse large B-cell lymphomas have activated B-cell-like subtype characteristics

Diffuse large B-cell lymphomas (DLBCLs) constitute a heterogeneous group of lymphomas in which germinal centre B-cell-like and activated B-cell-like subtypes can be discerned based on pathology, clinical presentation, and gene expression patterns. Testicular DLBCLs form an immune-privileged site-related subgroup of DLBCLs with an unfavourable prognosis. In the present study, cDNA microarray analysis, immunohistochemistry for CD10, Bcl6 and MUM1, and somatic hypermutation analysis of the immunoglobulin heavy chain gene rearrangements were used to determine the subtype of primary testicular DLBCL. Immunohistochemistry revealed 14/22 testicular DLBCLs with an activated B-cell-like immunophenotype and 8/22 with an ambiguous immunophenotype co-expressing CD10 and high levels of MUM1. cDNA microarray analysis of these 22 and four additional cases showed a uniform activated B-cell-like gene expression pattern for both immunophenotypes. Somatic hypermutation analysis of immunoglobulin heavy chain genes showed a very high mutation load in seven cases tested, but intraclonal heterogeneity was found at low level in only one of these cases. It is concluded that primary testicular DLBCLs have uniform activated B-cell-like subtype characteristics despite a number of cases showing an ambiguous immunophenotype.

Transcriptional profiling of the nuclear factor-kappaB pathway identifies a subgroup of primary lymphoma of the central nervous system with low BCL10 expression

Recent studies point to a role of nuclear factor (NF)-kappaB signaling in a subset of diffuse large B cell lymphomas. We have analyzed the expression of 21 genes encoding NF-kappaB family members, upstream modulators, and targets in 32 primary central nervous system lymphomas (PCNSLs) by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). Compared with nonmalignant germinal center centroblasts, expression of BCL10, REL, IAP1, and TRAF1 was significantly lower in PCNSLs, whereas that of BAX, BCLXL, BCL2, MALT1, CARD9, CARD10, CARD11, CARD14, CCND2, cFLIP, RELA, RELB, NFKB1, NFKB2, and IRF4 was higher. Hierarchical clustering of gene expression data revealed two distinct subgroups of PCNSLs, which were characterized by significantly different transcriptional levels, predominantly of BCL10, but also of REL and IAP1. Thus, these quantitative RT-PCR data with expression of genes of the NF-kappaB family as well as NF-kappaB-regulated genes together with immunohistochemical detection of nuclear RELA and REL indicate activation of the NF-kappaB pathway in PCNSLs, which may contribute to their high proliferative activity and the low level of apoptosis.

Chromosomal Translocations Fusing theBCL6Gene to Different Partner Loci Are Recurrent in Primary Central Nervous System Lymphoma and May Be Associated With Aberrant Somatic Hypermutation or Defective Class Switch Recombination

Primary central nervous system lymphomas (PCNSLs) are diffuse large B cell lymphomas confined to the brain. Only minimal data exist on chromosomal aberrations underlying PCNSLs. We studied 41 PCNSLs by fluorescence in situ hybridization for breakpoints affecting the BCL6 locus in chromosomal band 3q27. Of 37 cases evaluable, 14 (38%) carried a breakpoint in the BCL6 locus. Two of these showed juxtaposition of BCL6 to the IGH locus. In 4 cases, the BCL6 breakpoints were cloned using long-distance inverse polymerase chain reaction. All breakpoints were located within the BCL6 major translocation cluster. The translocation partners were the IGH gene in 14q32.33, the IGL gene in 22q11.22, and the histone 1 H4I gene in 6p22.1. In the fourth case, a deletion in 3q leads to loss of an 837-kb fragment extending from the first intron of BCL6 to the third intron of the lipoma-preferred partner (LPP) gene. This deletion may bring the BCL6 gene under the control of regulatory elements of the LPP gene or the miRNA-28 gene located in intron 4 of LPP. DNA sequence analysis of the junctional sequences provided evidence that aberrant class switch recombination or somatic hypermutation may be involved in the generation of BCL6 translocations.

Molecular cytogenetic analyses of immunoglobulin loci in nodular lymphocyte predominant Hodgkin's lymphoma reveal a recurrent IGH-BCL6 juxtaposition

Chromosomal translocations juxtaposing different oncogenes to the immunoglobulin (IG) loci are the hallmark of various B-cell lymphomas. Because the tumor cells in nodular lymphocyte predominant Hodgkin's lymphoma (NLPHL) are also derived from B cells, we examined whether NLPHL harbors chromosomal translocations that affect IG loci. Fluorescence in situ hybridization was applied to 24 NLPHL cases using probes flanking the IGH, IGK, and IGL loci as well as the BCL6 gene. Fourteen of these cases were additionally analyzed by combined immunofluorescence and fluorescence in situ hybridization. Chromosomal breakpoints in the IGH locus were detected in five NLPHL. All these cases also contained a BCL6 breakpoint. Triple-color interphase cytogenetics demonstrated the presence of an IGH-BCL6 juxtaposition, indicating a t(3;14)(q27;q32) in all five cases. There was no evidence for breakpoints affecting the IGK or IGL loci. Our results show that translocations juxtaposing the BCL6 oncogene next to the IGH locus are recurrent in NLPHL.