Clinical aspects and management of AIDS-related lymphoma

Diffuse Large B-Cell Lymphoma in the HIV Setting

Despite the widespread use of combined antiretroviral therapy (cART) and the subsequent decrease in AIDS-defining cancers, HIV-related lymphomas remain a leading cause of morbidity and mortality in people with HIV (PWH). Diffuse large B-cell lymphoma (DLBCL) is the most common non-Hodgkin lymphoma (NHL) subtype in PWH. This lymphoma is a heterogeneous disease including morphological variants and molecular subtypes according to the cell of origin or the mutation profile. In the pre-cART era, treatment with standard-dose chemotherapy induced high rates of toxicity and outcomes were very poor. The introduction of cART and the incorporation of infection prophylaxis allowed the use of conventional intensive chemotherapy regimens used in the general population, such as R-CHOP or R-EPOCH. The use of cART during chemotherapy treatment was initially controversial due to the potential risk of adverse drug-drug interactions. However, the availability of current cART regimens with less potential to cause drug interactions and evidence that cART improves survival rates in NHL strongly support the use of cART in PWH with DLBCL. Consequently, interdisciplinary collaboration between HIV specialists and hemato-oncologists for the management of potential interactions and overlapping toxicities between antiretroviral and antineoplastic drugs is crucial for the optimal treatment of PWH with NHL.

Epstein-Barr virus-driven lymphomagenesis in the context of human immunodeficiency virus type 1 infection

Epstein-Barr virus (EBV) is a ubiquitous human γ-herpes virus which establishes a life-long asymptomatic infection in immunocompetent hosts. In human immunodeficiency virus type 1 (HIV-1) infected patients, the impaired immunosurveillance against EBV may favor the development of EBV-related diseases, ranging from lymphoproliferative disorders to B cell non-Hodgkin's lymphomas (NHL). Antiretroviral therapy (ART) has significantly modified the natural course of HIV-1 infection, resulting in decreased HIV-1 plasmaviremia, increased CD4 lymphocytes, and decreased opportunistic infections, indicating a restoration of immune functions. However, the impact of ART appears to be less favorable on EBV-related malignancies than on other AIDS-defining tumors, such as Kaposi's sarcoma, and NHL remains the most common cancer during the ART era. EBV-driven tumors are associated with selective expression of latent oncogenic proteins, but uncontrolled lytic cycle with virus replication and/or reactivation may favor cell transformation, at least in the early phases. Several host's factors may promote EBV reactivation and replication; besides immunodepression, inflammation/chronic immune stimulation may play an important role. Microbial pathogen-associated molecular patterns and endogenous damage-associated molecular patterns, through Toll-like receptors, activate the immune system and may promote EBV reactivation and/or polyclonal expansion of EBV-infected cells. A body of evidence suggests that chronic immune stimulation is a hallmark of HIV-1 pathogenesis and may persist even in ART-treated patients. This review focuses on lymphomagenesis driven by EBV both in the context of the natural history of HIV-1 infection and in ART-treated patients. Understanding the mechanisms involved in the expansion of EBV-infected cells is a premise for the identification of prognostic markers of EBV-associated malignancies.

Epstein-Barr virus-associated primary central nervous system lymphoma in the Japanese population

The incidence of Epstein-Barr virus (EBV)-associated primary central nervous system (CNS) lymphoma in Japan was assessed using in situ hybridization of EBV-encoded small ribonucleic acid-1 (EBER-1) to identify the presence of EBV in 22 cases of formalin-fixed and paraffin-embedded primary CNS lymphoma. All cases were B-cell lymphoma. EBER-1 expression was observed in the nuclei of 3 of 22 primary CNS lymphoma cases (13.6%). The incidence of EBV-positive lymphoma in Japanese cases is higher than previously reported from Western countries. Patients with EBV-positive primary CNS lymphoma showed shorter survival than those with negative tumors (median 4 months vs. 26 months). EBER-1 in situ hybridization for the detection of EBV infection is rapid and reliable. Infrequent association suggests a different pathogenetic mechanism in the evolution of these tumors. Geographical differences in the incidence of EBV-associated primary CNS lymphoma may reflect epidemiological factors.

Phase 2 study of intrathecal, long-acting liposomal cytarabine in the prophylaxis of lymphomatous meningitis in human immunodeficiency virus-related non-Hodgkin lymphoma

BACKGROUND

Patients with aggressive non-Hodgkin lymphoma (NHL) develop central nervous system (CNS) progression or recurrence during the course of their disease. Patients with human immunodeficiency virus (HIV)-NHL often develop CNS progression despite the use of prophylaxis. Liposomal cytarabine (DepoCyte) has shown activity in lymphomatous meningitis, but there are limited data for prophylaxis.

METHODS

Between May 2006 and December 2008, a phase 2 study of intrathecal liposomal cytarabine was performed at the dose of 50 mg in 30 patients with HIV-NHL, with the aim of evaluating feasibility and activity for prophylaxis.

RESULTS

Liposomal cytarabine was well tolerated, with headache grade I to III being the most frequent side effect in 40% of patients. With a median follow-up of 10.5 months, only 1 (3%) patient developed a combined systemic and meningeal recurrence. The use of liposomal cytarabine allowed significant reduction of the number of lumbar injections in comparison to the standard schedules (around 50%), improving the quality of life of patients and reducing the professional exposure risk.

CONCLUSIONS

In this first study on prophylaxis of lymphomatous meningitis in HIV-NHL, liposomal cytarabine seems safe and active; it reduces by approximately 50% the number of lumbar punctures, and exposure risk for health staff as well.

Radiation therapy for HIV-associated diffuse large cell non-Hodgkin lymphoma

PURPOSE

To report the clinical experience with external beam radiotherapy (RT) for AIDS-related lymphoma (ARL) with or without the involvement of the central nervous system (CNS) in HIV-infected patients.

PATIENTS AND METHODS

Clinical outcome of 24 HIV-seropositive patients with ARL treated with RT from 1995 to 2004 was reviewed, testing factors associated with outcome.

RESULTS

After 1 and 5 years, the overall survival was 65% and 35%, respectively. The mean RT dose was 31 Gy after normalization to fractions of daily 2 Gy (range, 7.8-47.2 Gy). Radiotherapy dose was associated with survival in univariate (P = .04) and multivariate analysis (P = .01). Other factors in univariate analysis associated with outcome were viral load (VL), highly active antiretroviral therapy (HAART), ARL stage, and CNS involvement. Patients with CNS involvement achieved complete response in 46% and improved clinical performance was seen in 73%.

CONCLUSIONS

After chemotherapy, RT in combination with HAART is highly active, and RT should be encouraged especially after suboptimal responses to induction treatment.

Interventions for previously untreated patients with AIDS-associated non-Hodgkin's lymphoma

BACKGROUND

Human immunodeficiency virus (HIV) infection is known to be associated with an increased risk of non-Hodgkin's lymphoma (NHL). The majority of lymphomas (>80%) occurring during immunosuppression are aggressive B-cell in origin and have a high-to-intermediate histology grade. Treatment of NHL is not standardized.

OBJECTIVES

To assess the clinical effectiveness and safety of single agent or combination chemotherapy with or without immunochemotherapy (rituximab) and with or without highly active antiretroviral therapy (HAART) on overall survival (OS) and disease-free survival (DFS) for previously untreated patients with AIDS-related NHL.

SEARCH STRATEGY

The Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2009), MEDLINE (1966-March 6, 2009), EMBASE (1988-March 6, 2009), LlLACS (1982 to February 17, 2009), Gateway (March 6, 2009), and AIDSearch (2006 -February 2008) were used to identify published, potentially eligible trials. Further, we searched several electronic sources. For additional information see the Cochrane HIV/AIDS Group search strategy.

SELECTION CRITERIA

Randomized controlled trials (RCTs) assessing the effectiveness of systemic treatments for previously untreated AIDS-related NHL. There were no age or language restrictions.

DATA COLLECTION AND ANALYSIS

Authors independently assessed relevant studies for inclusion; four RCTs were selected. No meta-analysis was attempted due to clinical heterogeneity.

MAIN RESULTS

Four RCTs that included 857 patients (number range: 30 to 485) met the inclusion criteria. The studies have a high risk of bias; three RCTs were conducted in the United States and one was a multi-national, multi-centre RCT performed in France and Italy. One of the trials included only men. It was impossible to pool data for any of the outcomes due to the differences in the interventions assessed in these RCTs. Overall survival did not differ significantly between treatment groups. Disease free survival (DFS) was reported in two of the four RCTs, but it was not statistically significant between treatment groups.

AUTHORS' CONCLUSIONS

We found no evidence that the systemic interventions for untreated patients with AIDS-related NHL provide superior clinical effectiveness for improving OS, DSF, and tumour response rate; however, this conclusion is based on four RCTs with limited sample size and variable quality. More adequately powered RCTs that have low risk of bias are necessary to determine the real benefit or harm of interventions to treat this population. Overall survival (OS), DFS, and quality of life should be included as endpoints.

Serbian lymphoma study group (SLG): The prognosis of AIDS-related non-Hodgkin's lymphoma

BACKGROUND

The majority of patients with AIDS-related non-Hodgkin's lymphoma (ARL) present with advanced disease, aggressive histological type, B-symptoms, and often with an extranodal localization. The prognosis is generally poor. The use of highly active antiretroviral therapy (HAART), in combination with chemotherapy, has improved the outcome of ARL.

AIMS

The aims of this study were to detect prognostic factors for patients with ARL and estimate efficacy of concomitant chemotherapy and HAART on overall survival (OS) of these patients. Also, two different chemotherapy regimens have been tested: low dose (ld) mBACOD and CHOP.

METHODS

The study series involved 28 patients with ARL treated at the Clinical Center of Serbia in Belgrade during the period 1996-2006. Twenty-six patients had an aggressive type of lymphoma while 2 had an indolent type. Nineteen patients were treated with chemotherapy, 10 with ld mBACOD and 9 with CHOP. Concomitant HAART and chemotherapy were used in 14 patients.

RESULTS

This study demonstrated that significant factors for OS in patients with ARL were the high International Prognostic Index (P=0.019), previous AIDS event (P=0.04), aggressive histological type of NHL (P=0.007) and extranodal disease (P=0.04). The usage of concomitant HAART and chemotherapy had significant effect on median survival (90 months), compared with chemotherapy alone (10 months) (P=0.0002). The patients treated with CHOP had a better response than patients treated with ld mBACOD, but this difference was not significant.

CONCLUSIONS

Our data suggest that aggressive presentation of ARL implicates the need not only for more intensive chemotherapy regimens, but the concomitant usage of HAART, which should result in higher rates of OS in ARL patients.

Modern management of non-Hodgkin lymphoma in HIV-infected patients

Patients infected with human immunodeficiency virus (HIV) are at greater risk of developing non-Hodgkin lymphoma than the general population and aggressive B-cell lymphoma has become one of the most common of the initial acquired immunodeficiency syndrome (AIDS)-defining illnesses. This review considers the prognostic factors and new approaches to the treatment of patients with AIDS-related lymphoma (ARL). As highly active antiretroviral therapy (HAART) became available, the survival of many ARL patients has become comparable to that of HIV-negative patients. This is partly due to the decrease in the incidence of opportunistic infections and improved prognosis. Both developments can also be attributed to new treatment strategies for ARL, such as the use of effective infusional regimens, Rituximab combinations and high-dose therapy with autologous stem-cell transplantation for relapsed disease. However, unresolved issues persist, such as the optimal therapy for patients with Burkitt ARL or central nervous system involvement.

EBV-associated diseases in the AIDS patient

EBV-associated malignancies remain a considerable problem in HIV-infected individuals, even in the era of HAART. Although EBV is a common factor, each disease has a unique pathogenesis. Study of these diseases reveals the viral proteins expressed in the malignancies that might contribute to the development of the disease as well as the molecular basis for pathogenesis. It is likely that this knowledge will contribute to the development of novel therapeutics that will result in more favorable outcomes in the future.

High proportion of T-cell systemic non-Hodgkin lymphoma in HIV-infected patients in Lima, Peru

OBJECTIVE

Few reports have described the clinical and pathologic characteristics of HIV-related systemic non-Hodgkin lymphoma (sNHL) in developing countries. We aimed to determine these characteristics from a national HIV reference center in Peru and to evaluate factors associated with survival.

METHODS

A retrospective/prospective study of patients with HIV-related sNHL from the Guillermo Almenara General Hospital in Lima, Peru between 1993 and 2004. Clinical characteristics at diagnosis included age, gender, risk behavior, previous AIDS diagnosis, opportunistic diseases, previous highly active antiretroviral therapy, Karnofsky score, origin, clinical stage and B-cell symptoms of sNHL, and CD4 cell count. Cases of sNHL were classified according to the criteria of the World Health Organization.

RESULTS

Thirty-three cases were identified (26 male, age range: 38 +/- 10 years). Ten patients (30%) had a prior history of AIDS, 14 (42%) had a Karnofsky score of <or=70, and 18 (56%) had clinical stage IV sNHL. The CD4 cell count median value was 111 cells/microL (n = 25). Twenty-four cases (73%) were B-cell sNHL, and 9 cases (27%) were T-cell sNHL, both from peripheral cells. Nineteen cases of sNHL were extranodal: 15 of B-cell origin and 4 of T-cell origin. Eighteen cases of B-cell sNHL had diffuse large cell histologic findings, and all cases of T-cell sNHL were unspecified. Although there were no significant differences in clinical characteristics between phenotypes, patients with T-cell sNHL had less aggressive disease and a better survival rate.

CONCLUSIONS

A high proportion of T-cell sNHL cases was found at an HIV reference center in Peru. Clinical characteristics were similar between B-cell and T-cell lymphoma patients. T-cell lymphoma was less aggressive, and patients with T-cell lymphoma had a better survival rate than those with B-cell lymphoma.

AIDS-related malignancies: emerging challenges in the era of highly active antiretroviral therapy

Human immunodeficiency virus (HIV)-infected patients are at increased risk of developing cancer, particularly in the later stages of acquired immune deficiency syndrome (AIDS). Despite the advent of highly active anti-retroviral therapy (HAART), malignancy in this population is a leading cause of morbidity and mortality. Kaposi's sarcoma (KS) and AIDS-related non-Hodgkin's lymphoma (ARL) are the most common AIDS-defining malignancies. AIDS-related KS varies from minimal to fulminant disease. Treatment decisions for AIDS-related KS are guided largely by the presence and extent of symptomatic disease. In addition to HAART, excellent treatments exist for both localized disease (topical gel, radiotherapy, and intralesional therapy) and advanced disease (liposomal anthracyclines, paclitaxel). Novel therapies that have become available to treat AIDS-related KS include angiogenesis inhibitors and antiviral agents. ARL comprises a heterogeneous group of malignancies. With the immune restoration afforded by HAART, standard-dose chemotherapies now can be safely administered to treat ARL with curative intent. The role of analogous treatments used in HIV-negative patients, including monoclonal antibodies and autologous stem cell transplantation, requires further clarification in HIV-positive patients. HIV-infected patients also appear to be at increased risk for developing certain non-AIDS-defining cancers, such as Hodgkin's lymphoma and multiple myeloma. Although the optimal treatment of these neoplasms is at present uncertain, recent advances in chemotherapy, antiretroviral drugs, and supportive care protocols are allowing for more aggressive management of many of the AIDS-related cancers. This article provides an up-to-date review of the epidemiology, pathogenesis, clinical features, and treatment of various AIDS-related malignancies that are likely to be encountered by an oncologist practicing in the current HAART era.

AIDS-related cancer in the era of highly active antiretroviral therapy (HAART): a model of the interplay of the immune system, virus, and cancer. "On the offensive--the Trojan Horse is being destroyed"--Part B: Malignant lymphoma

The impact of highly active antiretroviral therapy (HAART) on the incidence of non-Hodgkin's lymphoma was less obvious initially, although primary central nervous system lymphoma (PCNSL) has dropped precipitously since the introduction of HAART. The pathogenesis of acquired immunodeficiency syndrome-related lymphoma is multifactorial. Epstein-Barr virus plays a significant role in these diseases, especially Burkitt lymphoma and PCNSL. Data regarding the effect of HAART on the natural history and treatment outcomes of these malignancies are emerging. The possibility of direct and indirect roles of human immunodeficiency virus in the carcinogenesis suggests that antiretroviral therapy may be an important component of the treatment for these malignancies. The simultaneous administration of HAART and chemotherapy does not appear to significantly alter the toxicity profile, although the information with respect to the interaction of HAART and chemotherapy is limited. The use of biological agents, for example, monoclonal antibody against CD-20, is being explored to improve the clinical outcome of this disease.

Human immunodeficiency virus type 1 Tat protein modulates cell cycle and apoptosis in Epstein-Barr virus-immortalized B cells

Patients infected with human immunodeficiency virus type 1 (HIV-1) develop a spectrum of B cell lymphoproliferative disorders ranging from polyclonal B cell activation to B cell lymphomas. While a direct role of Epstein-Barr virus (EBV) is well recognized for most of these lesions, recent findings have suggested that transactivator HIV-1 Tat protein might be involved in the pathogenesis of B cell lymphomas. Tat-expressing EBV-positive B cells were generated by transduction with a retroviral Tat-encoding vector. B(Tat+) cells expressed lower levels of anti-apoptotic protein Bcl-2 than parental and control B(Tat-) cells, generated by transduction with an empty retroviral vector, and were more prone to apoptosis upon serum withdrawal, as assessed by analysis of annexin V-stained cells and cleavage of poly-ADP-ribose-polymerase by caspase 3. Nevertheless, in serum starvation, B(Tat-) cells mainly exhibited the Rb hypo-phosphorylated form, underwent cell cycle arrest, and grew in single cell suspension, while B(Tat+) cells displayed the Rb hyper-phoshorylated form, progressed throughout the cell cycle, and retained the ability to grow in small clumps. Finding that B(Tat+) cells maintained proliferative capacity upon serum withdrawal suggests that cells expressing Tat have growth advantages among the EBV-driven cell proliferations and may originate B cell clones with more oncogenic potential.

Feline intracranial neoplasia: retrospective review of 160 cases (1985-2001)

The purpose of this study was to determine the frequency of different tumor types within a large cohort of cats with intracranial neoplasia and to attempt to correlate signalment, tumor size and location, and survival time for each tumor. Medical records of 160 cats with confirmed intracranial neoplasia evaluated between 1985 and 2001 were reviewed. Parameters evaluated included age, sex, breed, FeLV/FIV status, clinical signs, duration of signs, number of tumors, tumor location(s), imaging results, treatment, survival times, and histopathologic diagnosis. Most of the cats were older (11.3 +/- 3.8 years). Primary tumors accounted for 70.6% of cases. Metastasis and direct extension of secondary tumors accounted for only 5.6 and 3.8% of cases, respectively. Twelve cats (7.5%) had 2 or more discrete tumors of the same type, whereas 16 cats (10.0%) had 2 different types of intracranial tumors. The most common tumor types were meningioma (n = 93, 58.1%), lymphoma (n = 23, 14.4%), pituitary tumors (n = 14, 8.8%), and gliomas (n = 12, 7.5%). The most common neurological signs were altered consciousness (n = 42, 26.2%), circling (n = 36, 22.5%), and seizures (n = 36, 22.5%). Cats without specific neurological signs were common (n = 34, 21.2%). The tumor was considered an incidental finding in 30 (18.8%) cats. In addition to expected relationships (eg, meninges and meningioma, pituitary and pituitary tumors), we found that lesion location was predictive of tumor type with diffuse cerebral or brainstem involvement predictive of lymphoma and third ventricle involvement predictive of meningioma.

[Muscle tumor in a girl with HIV infection: extranodal non-Hodgkin's lymphoma]

Non-Hodgkin's lymphomas are the most common cancers in children with human immunodeficiency virus (HIV) infection. Extranodal disease is the most common form of clinical presentation. Treatment with aggressive chemotherapy and highly active antiretroviral therapy has improved the prognosis of these children. We present a 10-year-old severely immunocompromised girl with HIV infection and non-Hodgkin's lymphoma manifested by a muscle mass.

Epidemiology of non-Hodgkin lymphomas and other haemolymphopoietic neoplasms in people with AIDS

HIV-infected individuals have a high risk of developing non-Hodgkin lymphoma (NHL). In Europe, the prevalence of AIDS with a concurrent NHL diagnosis increased from 3.6% to 5.4% between 1994 and 2000. In population-based record linkages between cancer registries and AIDS registries in the USA, Italy, and Australia, the relative risks of NHL in people with AIDS ranged between 15 for low-grade and T-cell NHL and 400 for high-grade NHL. The corresponding relative risk of Hodgkin's disease was about 10, whereas the risks for multiple myeloma and leukaemias were in the range 2 to 5. Since the introduction of highly active antiretroviral therapy in the more developed countries (1996), most studies have suggested a decline in the incidence of some types of NHL, most notably the primary brain form. In studies from Africa, the risk of HIV-associated NHL is about ten times less than that in the more developed countries, but underascertainment and earlier death from other AIDS-related illnesses may explain the relative lack of HIV-associated lymphomas.

Acquired immunodeficiency syndrome-associated lymphomas are efficiently lysed through complement-dependent cytotoxicity and antibody-dependent cellular cytotoxicity by rituximab

Rituximab (Mabthera) and alemtuzumab (Campath(R), Mabcampath(R)) are non-conjugated IgG1 therapeutic monoclonal antibodies directed against the CD20 and CD52 surface antigens respectively. They are presently used in the therapy of indolent B-cell non-Hodgkin's lymphoma (B-NHL) and of B-cell chronic lymphocytic leukaemia, and are thought to act mainly through complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC). Here we have analysed the capacity of these two monoclonal antibodies to lyse cell lines of acquired immunodeficiency syndrome (AIDS)-related B-NHL through either complement activation or antibody-dependent cytotoxicity. Rituximab strongly activated both CDC and ADCC against CD20-positive AIDS-NHL cells lines, inducing up to 60-98% and 20% specific lysis respectively. In contrast, alemtuzumab was a poor activator of CDC, even in the AIDS-NHL cell lines expressing high amounts of CD52, leading to a lysis of only 1-30%, whereas it was at least as strong as rituximab in inducing ADCC of the same lines (up to 30% specific lysis). Altogether, these data offer a first in vitro rationale supporting the therapeutic use of rituximab for CD20-positive AIDS-NHL.

AIDS-related non-Hodgkin's lymphomas: from pathology and molecular pathogenesis to treatment

In the highly active antiretroviral therapy (HAART) era, AIDS-related non-Hodgkin's lymphomas (AIDS-NHL) and their treatment still represent an open issue, because HAART may not be sufficient to prevent the development of NHL. The present spectrum of AIDS-NHL includes systemic lymphomas, primary central nervous system lymphomas, and 2 rare entities, primary effusion lymphomas (PEL) and plasmablastic lymphomas of the oral cavity. The vast majority of systemic AIDS-NHL belongs to 3 high-grade B-cell lymphomas: Burkitt's lymphoma (BL), immunoblastic lymphoma (IBL), and large-cell lymphoma (LCL). The pathologic heterogeneity of AIDS-NHL is correlated with the heterogeneity of the molecular lesions associated with these lymphomas. The molecular lesions associated with AIDS-BL involve activation of c-MYC inactivation of p53, and infection by Epstein-Barr virus (EBV). EBV infection occurs in 40% of LCL cases and in 90% of IBL cases. Rearrangements of BCL-6 are detected in 20% of AIDS-LCL cases. In the presence of EBV infection, BCL-6 expressing AIDS-LCL fails to express the latent membrane protein 1 (LMP1) antigen. Conversely, AIDS-IBL are characterized by absent BCL-6 expression, absence of BCL-6 rearrangements, and frequent expression of LMP1. Consistently, the molecular pathways of viral infection and lesions of cancer-related genes associated with AIDS-NHL vary substantially in different clinicopathologic categories of the disease. The marked degree of biologic heterogeneity of AIDS-NHL is highlighted by their histogenetic differences, because AIDS-NHL are related to distinct B cell subsets (ie, germinal center [GC] or post-GC B cells). The phenotypic pattern of AIDS-BL and systemic AIDS-LCL closely reflects B cells residing in the GC, namely centroblasts and centrocytes. Conversely, the phenotype of AIDS-IBL, either systemic or localized primarily to the central nervous system, and AIDS-PEL reflects post-GC B cells in all cases. New information on the molecular and virologic pathogenesis of AIDS-NHL may serve as a point of attack for pathogenic-driven therapies. Moreover, a greater knowledge of other biologic features of these tumors may help investigators identify new potential targets for "intelligent" therapies.

Spinal cord involvement of primary central nervous system lymphomas: histopathological examination of 14 autopsy cases

The brain and spinal cord from 14 patients with primary central nervous system lymphomas (PCNSL) were systematically examined to determine the distribution and frequency of spinal cord lesions. Spinal cord involvement was observed in four cases (cases 1-4). In cases 1 and 2, tumor cells were spread widely in the brain and extended downward to C4 and Th8 in the spinal parenchyma and to C2 and Th2 in the subarachnoid space (SAS), respectively. In case 3, tumors were found in the cerebrum but not in the cerebellum or brainstem. In the spinal cord there was massive subarachnoid involvement from C2 to L4 and localized parenchymal invasion from Th8 to L4. In case 4, tumors were found in the parenchyma from brainstem to Th2 and in the SAS all around the cord. Diffuse subarachnoid proliferation with parenchymal invasion via the Virchow-Robin space was found in the spinal cord. The route of tumor spread in cases 1 and 2 was considered to be intra-parenchymal invasion from the medulla oblongata to the spinal cord because the cord lesions had continuity with the brain lesions. In contrast, the cord lesions in cases 3 and 4 were considered to be spread via the CSF because the lesions had no continuity with the brain lesions in case 3, and spinal SAS involvement was more extensive than the parenchymal lesions in both cases. These findings suggest that spinal cord involvement is not a rare event in PCNSL and that there are two routes of spread: direct invasion from the medulla oblongata and dissemination via the CSF.