Analysis of chromosomal copy number changes and oncoprotein expression in primary central nervous system lymphomas: frequent loss of chromosome arm 6q

Introduction of novel agents in the treatment of primary CNS lymphoma

Novel insights into the pathophysiology of primary central nervous system lymphoma (PCNSL) have identified the B-cell receptor and Toll-like receptor pathway as well as immune evasion and suppressed tumor immune microenvironment as a key mechanism in the pathogenesis of PCNSL. Small molecules and novel agents targeting these aberrant pathways have been introduced into clinical trials targeting the recurrent or refractory PCNSL patient population. Agents like the Bruton tyrosine kinase (BTK) inhibitor ibrutinib or immunomodulatory drugs (IMiDs) like pomalidomide and lenalidomide have shown promising high response rates in the salvage setting. Here, we give an overview about the recent, exciting developments in PCNSL and summarize the results of clinical trials using novel agents in the recurrent and refractory salvage setting, which include immune checkpoint inhibitors, IMiDs, as well as BTK, phosphatidylinositol-3 kinase, and mammalian target of rapamycin inhibitors.

Treatment of Primary Central Nervous System Lymphoma: From Chemotherapy to Small Molecules

Primary central nervous system lymphoma (PCNSL) is a rare form of extranodal non-Hodgkin lymphoma that is typically confined to the brain, eyes, and cerebrospinal fluid (CSF) without evidence of systemic spread. PCNSL is an uncommon tumor, and only four randomized trials and one phase III trial have been completed so far, all in the first-line setting. The prognosis of patients with PCNSL has improved during the past few decades with the introduction of high-dose methotrexate (HD-MTX), which now serves as the backbone of all first-line treatment regimens. Despite recent progress, results after treatment are durable in half of patients, and therapy can be associated with late neurotoxicity. Novel insights into the pathophysiology of PCNSL have identified the B-cell receptor (BCR) pathway as a key mechanism in the pathogenesis of PCNSL. The use of novel agents targeting components of the BCR pathway, namely the Bruton tyrosine kinase (BTK) inhibitor ibrutinib, and immunomodulatory drugs (IMIDs) like lenalidomide and pomalidomide, has so far been limited to patients who have recurrent/refractory PCNSL with promising high response rates. Within the past 5 years, there has been a peak in clinical trials investigating small molecules and novel reagents in the recurrent/refractory setting, including immune checkpoint inhibitors, IMIDs, and BTK and PI3K/AKT/mTOR inhibitors.

The Challenge of Primary Central Nervous System Lymphoma

Primary central nervous system (CNS) lymphoma is a challenging subtypes of aggressive non-Hodgkin lymphoma. Emerging clinical data suggest that optimized outcomes are achieved with dose-intensive CNS-penetrant chemotherapy and avoiding whole brain radiotherapy. Anti-CD20 antibody-based immunotherapy as a component of high-dose methotrexate-based induction programs may contribute to improved outcomes. An accumulation of insights into the molecular and cellular basis of disease pathogenesis is providing a foundation for the generation of molecular tools to facilitate diagnosis as well as a roadmap for integration of targeted therapy within the developing therapeutic armamentarium for this challenging brain tumor.

Primary intracranial lymphomas

BACKGROUND

Primary CNS lymphoma (PCNSL), a rare form of aggressive extranodal non-Hodgkin's lymphoma (NHL), has increased in incidence during the last three decades and occurs in both immune compromised and immune competent hosts. It has an overall poor prognosis.

OBJECTIVE

This study attempts to further delineate the clinico-pathological, immunohistochemical and radiological profile of PCNSL at Jeddah to King Faisal Hospital and Research Center.

METHODS

Computerized search through the archives of King Faisal Hospital and Research Centre between July 2000- December 2012 identified 15 patients with pathologically confirmed PCNSL. These were analyzed retrospectively. Their clinico-pathological, immunohistochemical and radiological data were analyzed.

RESULTS

Of the 15 PCNSL patients, 8 (53.3%) were females and 7 (46.6%) were males. There was female predilection especially in the age group of 40-59 years. Mean age at diagnosis for all patients was 50.4 years. There was no patient in the pediatric age group. The most common location in the brain was the frontal region in 7 patients (46.6%), 7 (46.6%) had multiple intracranial masses; all 15 (100%) were Non Hodgkin B-cell lymphomas, among which 13 (86.6%) were diffuse large B-cell lymphomas. All 15 (100%) cases showed diffuse and strong positivity for CD 45, and CD 20. Fourteen patients were immune competent while one was immune compromised.

CONCLUSIONS

PCNSL often occurs in middle-aged and aged patients. There is female predilection especially in the middle age. Frontal region is the most common location with diffuse large B-cell lymphoma being the predominant subtype.

New approaches in primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) has long been associated with an inferior prognosis compared to other aggressive non-Hodgkin's lymphomas (NHLs). However, during the past 10 years an accumulation of clinical experience has demonstrated that long-term progression-free survival (PFS) can be attained in a major proportion of PCNSL patients who receive dose-intensive consolidation chemotherapy and avoid whole brain radiotherapy. One recent approach that has reproducibly demonstrated efficacy for newly diagnosed PCNSL patients is an immunochemotherapy combination regimen used during induction that consists of methotrexate, temozolomide, and rituximab followed by consolidative infusional etoposide plus high-dose cytarabine (EA), administered in first complete remission (CR). Other high-dose chemotherapy-based consolidative regimens have shown efficacy as well. Our goal in this review is to update principles of diagnosis and management as well as data regarding the molecular pathogenesis of PCNSL, information that may constitute a basis for development of more effective therapies required to make additional advances in this phenotype of aggressive NHL.

Progress in central nervous system lymphomas

Until recently, primary central nervous system lymphoma (PCNSL) was associated with a uniformly dismal prognosis. It is now reasonable to anticipate long-term survival and possibly cure for a significant proportion of patients diagnosed with PCNSL. Accumulated data generated over the past 10 years has provided evidence that long-term progression-free survival (PFS) can reproducibly be attained in a significant fraction of PCNSL patients that receive dose-intensive chemotherapy consolidation, without whole brain radiotherapy. One consolidative regimen that has reproducibly demonstrated promise is the combination of infusional etoposide plus high-dose cytarabine (EA), administered in first complete remission after methotrexate, temozolomide and rituximab-based induction. Given evolving principles of management and the mounting evidence for reproducible improvements in survival rates in prospective clinical series, our goal in this review is to highlight and update principles in diagnosis, staging and management as well as to review data regarding the pathogenesis of central nervous system lymphomas, information that is likely to constitute a basis for the implementation of novel therapies that are requisite for further progress in this unique phenotype of non-Hodgkin lymphoma.

High-resolution genomic copy number profiling of primary intraocular lymphoma by single nucleotide polymorphism microarrays

Primary intraocular lymphoma (PIOL) is a rare lymphoma. Because of difficulties in obtaining tissue samples, little is known about the disease's genetic features. In order to clarify these features, we carried out single nucleotide polymorphism array karyotyping of IOL using genomic DNA extracted from vitreous fluid. We analyzed 33 samples of IOLs consisting of 16 PIOLs, 12 IOLs with a central nervous system (CNS) lesion at diagnosis (IOCNSL), and five secondary IOLs following systemic lymphoma. All were B-cell type. We identified recurrent copy number (CN) gain regions in PIOLs, most frequently on chromosome 1q followed by 18q and 19q. Chromosome 6q was the most frequent loss region. Although these CN gain regions of PIOL were in common with those of IOCNSL, loss of 6q22.33 containing PTPRK and 9p21.3 containing CDKN2A were more frequently deleted in IOCNSL. Large CN loss in 6q was detected in three of four PIOL patients who had early CNS development and short survival periods, whereas long-term survivors did not have such deletions. There was a correlation between gain of the IL-10 gene located on 1q and intravitreal interleukin-10 concentration, which was higher in IOL than in benign uveitis. The results suggest that IOCNSL is a highly malignant form of PIOL that infiltrates into the CNS at an early stage. They also indicate that genetic differences between PIOL and primary CNS lymphoma need to be clarified.

Beyond high-dose methotrexate and brain radiotherapy: novel targets and agents for primary CNS lymphoma

BACKGROUND

While there has been significant progress in outcomes for patients diagnosed with primary central nervous system (CNS) lymphoma (PCNSL), survival rates will likely plateau with the current armamentarium of agents used to treat these patients. Moreover, given that PCNSL increasingly impacts an older population, a significant proportion of patients are not eligible for intensive therapies such as high-dose chemotherapy or whole-brain radiation. There is a need for the development of novel agents, which target key survival pathways in order to continue to make progress in this disease.

PATIENTS AND METHODS

We reviewed the key molecular pathways and genomic aberrations in PCNSL in order to identify candidate targets. We focused on molecules and pathways that have been identified and confirmed by more than one investigator or methodology.

RESULTS

While PCNSL tumors usually express a BCL6+, MUM1+ 'activated, germinal center' immunophenotype, they exhibit multiple shared genetic properties with ABC-type diffuse large B-cell lymphomas. Candidate targets and pathways include NFkB, the B-cell receptor, the JAK/STAT pathway, IRF4, BCL-6 as well as PIM kinases. Elements of the tumor microenvironment that may be exploited therapeutically include chemokine pathways, as well as macrophage and T-cell responses.

CONCLUSIONS

There is a significant need for developing novel therapies in PCNSL, given that an increasing proportion of patients are not eligible for high-dose chemotherapy and brain radiation is associated with detrimental cognitive side-effects. We provide an overview of potential drug targets and novel agents that may be integrated with existing strategies in order to make further progress in this disease.

How I treat CNS lymphomas

The pathogenesis of primary and secondary central nervous system (CNS) lymphoma poses a unique set of diagnostic, prognostic, and therapeutic challenges. During the past 10 years, there has been significant progress in the elucidation of the molecular properties of CNS lymphomas and their microenvironment, as well as evolution in the development of novel treatment strategies. Although a CNS lymphoma diagnosis was once assumed to be uniformly associated with a dismal prognosis, it is now reasonable to anticipate long-term survival, and possibly a cure, for a significant fraction of CNS lymphoma patients. The pathogenesis of CNS lymphomas affects multiple compartments within the neuroaxis, and proper treatment of the CNS lymphoma patient requires a multidisciplinary team with expertise not only in hematology/oncology but also in neurology, neuroradiology, neurosurgery, clinical neuropsychology, ophthalmology, pathology, and radiation oncology. Given the evolving principles of management and the evidence for improvements in survival, our goal is to provide an overview of current knowledge regarding the pathogenesis of CNS lymphomas and to highlight promising strategies that we believe to be most effective in establishing diagnosis, staging, and therapeutic management.

Genomic profiling combined with gene expression profiling in primary central nervous system lymphoma

Of the genetic changes in primary central nervous system lymphoma (PCNSL), little is known. To detect copy number alterations and differentially expressed genes in PCNSL, we analyzed a total of 12 PCNSL samples with high-resolution array-based comparative genomic hybridization and performed expression profiling in 7 of the 12 samples. The most frequent deletion found in 8 patients (66.7%) occurred in 9p21.3 containing CDKN2A. We compiled the top 96 genes (family-wise error rate, P < .05) showing the greatest differential expression between PCNSL and normal lymph node tissues. From these, we selected 8 candidate genes (NPFFR2, C4orf7, OSMR, EMCN, TPO, FNDC1, COL12A1, and MSC) in which expression changes were associated with copy number aberrations. All 8 genes showed both down-regulation in expression microarray and deletion in array-based comparative genomic hybridization analyses. These genes participate in cell signaling or cell adhesion. In addition, low mRNA expression of C4orf7 was significantly associated with poor survival (P = .0425). Using gene set enrichment analysis, we identified several signal transduction pathways, such as Janus kinase-signal transducers and activators of transcription pathway and adhesion-related pathways, which may be involved in pathogenesis of PCNSL. In conclusion, this study identified novel tumor suppressor genes that may serve as therapeutic targets of PCNSL.

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.

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.

A virtual tissue bank for primary central nervous system lymphomas in immunocompetent individuals

Primary central nervous system lymphoma (PCNSL) is a rare form of extranodal non-Hodgkin's lymphoma with continuously increasing incidence in both immunosuppressed and immunocompetent individuals. PCNSL is a very aggressive tumor with a poor outcome, and its clinical outcome is much worse than for nodal lymphomas. Differently from lymphomas arising in lymph nodes or in other extranodal sites, the treatment of PCNSL remains very unsatisfactory. Current biologic knowledge of PCNSL is still limited and several fundamental questions remain to be answered. This is mainly due to the paucity of PCNSL material for adequate translational research. With the aim of providing biologic material to investigators interested in PCNSL, we have implemented a virtual tissue bank (VTB) for PCNSL in immunocompetent patients. After registration, the VTB is accessible via any web browser at www.ielsg.org. Only anonymous data are centralized at the website of the International Extranodal Lymphoma Study Group, whilst the pathologic material is maintained at the local pathology institutes.

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.

Frequent loss of heterozygosity at 6q in pheochromocytoma

Multiple genetic alterations have been associated with pheochromocytoma (PCC). Most PCCs are sporadic, but they also occur in inherited tumor syndromes, including von Hippel-Lindau disease. Although the etiology of most inherited PCCs is well documented, little is known about the etiology of sporadic tumors. Mutations of those genes that harbor germ-line mutations in familial cases cover only 10% to 15% of somatic mutations in sporadic PCCs. A previous cytogenetic analysis indicated frequent loss of 6q in sporadic PCCs. We therefore investigated in detail 18 PCCs using 22 microsatellite markers spanning 6q to search for the presence of allele deletions and identify specific regions likely to contain tumor suppressor genes involved in PCC. Moreover, we sought to compare PCC with capillary hemangioblastoma, another von Hippel-Lindau disease-associated tumor that we previously found to harbor frequent loss of heterozygosity (LOH) at 6q. Our study revealed a high frequency (13/18; 72%) of overall 6q LOH in PCCs. Loss of heterozygosity at 6q was observed in 6 benign (6/9; 67%) and 7 borderline (7/9; 78%) tumors. We identified 2 regions where LOH or allelic imbalance was common (ie, 6q14 [9/18; 50%] and 6q23-24 [6/18; 33%]). We further focused the search using markers specific for the ZAC1 gene region located at 6q24-25. Altogether, for all 6q23-25 markers, including the ZAC1-specific ones, LOH or allelic imbalance was observed in 50% (9/18) of the PCCs. Similar to our findings for capillary hemangioblastomas, our data for the first time suggest that one or several tumor suppressor genes located at 6q, particularly at 6q23-24, may play a role in the tumorigenesis of PCCs.

Array comparative genomic hybridization reveals a very high frequency of deletions of the long arm of chromosome 6 in testicular lymphoma

Despite the fact that numerous studies have been performed on diffuse large B-cell lymphoma (DLBCL), only few have concerned extranodal lymphomas occurring in the testis. We performed a cytogenetic and molecular study of 17 testicular non-Hodgkin lymphomas, of which 14 were proven primary DLBCL of the testis. Cytogenetic analysis revealed in 8 out of 11 evaluable cases a structural abnormality of the long arm of chromosome 6, with deletion or addition of material of unknown origin, and with breakpoints spanning the region 6q12-6q23. The cytogenetic findings were confirmed by fluorescent in situ hybridization (FISH) with a chromosome 6 painting probe. Using array based-comparative genomic hybridization on 16 evaluable cases, including 5 cases not tested by cytogenetics or FISH, 14 (88%) showed chromosome 6q deletions. We identified two regions of minimal deletion (RMD), at 104-113 Mb (6q16.3-q21) and 137.5-138.8 Mb (6q23.3), respectively. In one case, we observed a 2.7 Mb homozygous deletion ranging from 135.3 to 138.0 Mb that partly overlapped with the RMD at 6q23.3. Our study indicates that 6q deletions play a major pathogenetic role in DLBCL of the testis and that many of these deletions are part of unbalanced translocations.

Primary central nervous system lymphoma

Primary central nervous system lymphoma is a stage 1E non-Hodgkin's lymphoma confined to the nervous system. It is seen in immunocompetent and immunodeficient populations, the latter group associated with the Epstein-Barr virus. Primary central nervous system lymphoma can affect the brain, leptomeninges, spinal cord or eyes. The institution of high-dose methotrexate-based regimens and whole-brain radiation therapy has significantly increased survival, but neurotoxicity is high in patients over 60 years of age. Despite these advances, 50% of patients initially treated will relapse. Recent investigations include the use of rituximab (immunotherapy) and stem-cell transplantation, as well as regimens without whole-brain radiation therapy in the elderly. The optimal treatment regimen is yet to been determined.

Prognostic factors in primary central nervous system lymphomas

Efforts to identify survival predictors in primary central nervous system lymphoma (PCNSL) have produced isolated, unconfirmed observations in small retrospective and prospective series. Age and performance status are two unanimously accepted prognostic factors. These and other independent predictors of survival were used by the International Extranodal Lymphoma Study Group (IELSG) to establish a prognostic scoring system able to distinguish risk groups in PCNSL. The IELSG score will improve further with better knowledge of these malignancies, especially with the inclusion of molecular and pharmacogenetic variables able to identify lymphomas with different chemosensitivities or degrees of aggressiveness. In the years ahead, a well-established prognostic score will allow the separation of patients into risk groups, which could result in the application of risk-tailored therapeutic strategies.

Gains and overexpression identify DEK and E2F3 as targets of chromosome 6p gains in retinoblastoma

The paediatric eye tumour retinoblastoma is initiated by inactivation of RB1, a tumour suppressor on chromosome 13q. In addition to RB1 loss, many retinoblastomas show other genetic alterations including gains on chromosomes 6p21-pter and 1q31-q32. Recently, the minimal region of gains on chromosome 6 was narrowed to band p22. We examined genomic gains and expression changes in primary retinoblastomas to identify potential target genes in 6p22. Quantitative multiplex PCR detected copy numbers > or = 3 in 25 (33%) tumours and no gains in 31 of 76 (40%) tumours. The remaining 20 (26%) samples showed gains only at some loci, most often including E2F3 and DEK in 6p22.3. Analysis of RNA from 21 primary retinoblastomas showed that expression levels of these and some other genes in 6p22 correspond to DNA gains. However, KIF 13A, a reported candidate oncogene on 6p, was expressed at low levels or absent. Clinical manifestation of tumours with gains at all 6p22 loci was distinct in that distribution of age at diagnosis was markedly shifted to older age compared to tumours with no or partial gains. In summary, our results suggest that DEK and E2F3 are potential targets of 6p gains in retinoblastoma.

Differential Diagnosis of Waldenström's Macroglobulinemia and Other B-Cell Disorders

Waldenstrom's macroglobulinemia (WM) is characterized by lymphoplasmacytic infiltration of bone marrow and/or other tissues and by the presence of serum monoclonal immunoglobulin M ([IgM], without cutoff limit). Differential diagnosis from other B-cell disorders (BCDs) is usually easy based on clinical, morphologic, histopathologic, immunophenotypic, and genetic features. However, all BCDs potentially produce monoclonal IgM. In this study we reviewed the medical files of 130 patients with IgM-secreting BCDs. Eighty-four patients were diagnosed with WM, 5 with IgM-monoclonal gammopathy of undetermined significance (MGUS), and 41 with other BCDs (9 with B-cell chronic lymphocytic leukemia, 5 with small lymphocytic lymphoma, 14 with marginal zone lymphoma, 5 with mantle-cell lymphoma, 2 with follicular lymphoma, 2 with diffuse large B-cell lymphoma, 2 with cryoglobulinemia, and 2 with low-grade lymphoma not otherwise specified). Median IgM levels were 3215 mg/dL in WM, 840 mg/dL in IgM-MGUS, and 285 mg/dL in other BCDs (5 had IgM levels > 1500 mg/dL). In 10% of non-WM BCDs, monoclonal IgM was found only when more sensitive immunofixation methods were used. Forty-four percent of patients with BCDs (splenic marginal zone lymphoma or small lymphocytic lymphoma) had diagnoses that corresponded to that of WM. Careful diagnosis requires the concomitant evaluation of all parameters of BCDs together. Marginal zone lymphoma is the most frequently overlapping entity. Special attention should be given to mantle cell lymphoma in its atypical forms. Research in this field should continue to further clarify the disease entities that overlap with WM. New technology such as gene-expression profile techniques may contribute to this purpose.

SHP-1 expression in primary central nervous system B-cell lymphomas in immunocompetent patients reflects maturation stage of normal B cell counterparts

SHP-1 is an important negative regulator involved in signaling through receptors for cytokine/growth factors, and differential patterns of SHP-1 expression in several types of B-cell lymphomas closely resemble the patterns seen in their normal B cell counterparts. In an effort to elucidate the origin of primary central nervous system lymphomas (PCNSL), the present study assessed 32 cases of PCNSL. Tumors were subclassified according to WHO classification and were evaluated by immunohistochemistry for expression of antigens associated with germinal center (GC) (CD10, Bcl-6) and non-GC stages (SHP-1, CD138). Twenty-nine cases showed diffuse large-cell centroblastic morphology, whereas three cases showed diffuse large-cell immunoblastic morphology. The immunophenotypes of PCNSL were as follows: SHP-1+/Bcl-6-/CD10-/CD138- (12 of 32 cases); SHP-1+/Bcl-6+/CD10-/CD138- (15 of 32 cases); SHP-1+/Bcl-6+/CD10+/CD138- (two of 32 cases); SHP-1+/Bcl-6-/CD10+/CD138- (one of 32 cases); and SHP-1-/Bcl-6-/CD10-/CD138- (two of 32 cases). These results indicate that PCNSL might be distinct lymphomas that originate from a late germinal center to an early postgerminal center.

Diagnosis and treatment of primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is an uncommon form of non-Hodgkin's lymphoma (NHL) that has been increasing in incidence over the past three decades. Unlike systemic extranodal NHL, the response to therapy for PCNSL patients has been somewhat unsatisfactory. However, methotrexate-based chemotherapy and whole-brain radiotherapy have improved the outcome of patients. Unfortunately, treatment-related neurotoxicity is common, especially in the elderly. Although progress has been made in treating PCNSL, there remains no optimal methotrexate dose or frequency. Treatment of recurrence also remains controversial. These important questions have prompted several clinical studies looking at novel ways to intensify chemotherapy and limit neurotoxicity.

Leptomeningeal precursor B-cell lymphoblastic lymphoma in a child with minimal bone marrow involvement

The authors report an unusual presentation of a leptomeningeal lymphoblastic lymphoma in a 6-year-old boy with headache and papilledema as the only initial manifestations. The diagnosis was confirmed by the presence of precursor B-cell lymphoblasts in the cerebrospinal fluid, with no cerebral mass and with only 9% phenotypically identical blasts in the bone marrow. This patient was treated on a high-risk ALL protocol with intensive systemic/intrathecal chemotherapy plus cranial irradiation, and he remained in complete remission 6 months after his initial diagnosis.