Primary central nervous system lymphoma of T-cell origin: description of two cases and review of the literature

Primary peripheral T-cell central nervous system lymphoma

BACKGROUND

Primary peripheral T-cell central nervous system lymphoma (PCNSL) is a rare, aggressive tumor that arises in the craniospinal axis and has an increased risk in individuals who are immunocompromised. This lesion often mimics other benign and malignant processes on radiographic imaging, leading to misdiagnosis and delays in treatment. We present a case of a patient with a history of Sjögren's syndrome and progressive neurologic symptoms who underwent craniotomy for diagnosis.

CASE DESCRIPTION

A 61-year-old woman with a history of Sjögren's syndrome, progressive aphasia, left facial droop, and right-sided paresthesias for 4 months presented for evaluation and management. An enhancing, infiltrative lesion in the left frontal lobe with underlying vasogenic edema was appreciated and suggestive of a primary or metastatic neoplasm. The patient underwent an open biopsy for further evaluation of the lesion. Extensive histopathologic evaluation revealed a diagnosis of T-cell PCNSL. The patient was started on induction methotrexate and temozolomide followed by consolidative radiotherapy.

CONCLUSION

Autoimmune conditions are a risk factor for T-cell PCNSL development. T-cell PCNSL has radiographic and gross histologic features that are consistent with a broad differential, including gliomas and inflammatory processes. Prompt diagnosis and extensive histopathological evaluation is essential to ensure appropriate treatment.

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.

Primary central nervous system T-cell lymphoma: An analysis from the surveillance, epidemiology, and end results program

BACKGROUND

Primary central nervous system T-cell lymphoma (PCNSTCL) is a rare neoplasm with few data regarding its common features and survival characteristics.

OBJECTIVE

To explore the Surveillance, Epidemiology, and End Results 18 (SEER 18) database to determine the epidemiology of PCNSTCL.

METHODS

The SEER 18 registry database was queried to identify patients diagnosed with PCNSTCL from 1973 to 2014 and extract their information. Age-specific rates and Kaplan-Meier overall survival (OS) were calculated. A Cox proportional hazards model was applied to investigate relationships between various demographic/treatment variables and OS.

RESULTS

The age-specific incidence rates were higher in the older population (≥60 years). Among 59 PCNSTCL cases from the SEER 18, the mean age at presentation was 55.8 years (SD, ±17.95), with a male predominance (1.36:1.00). The median follow-up was 8 months, and the median OS was 8 months (SE, ±4.162). The 1-, 3-, and 5-year OS was 46.3% [95% CI, 33.4%-59.2%], 32.8% [20.3%-45.3%], and 32.8% [20.3%-45.3%], respectively. Seventeen of the 59 patients survived at last follow-up. Patients < 60 years had a greater 3-year OS compared with patients ≥ 60 years (52.6% [33.6%-71.6%] vs 13.9% [1.4%-26.4%]. Multivariate analysis has demonstrated that only age at diagnosis (≥60/<60 years) exhibited a significant relationship with OS (HR, 3.495 [1.688-7.235];p = 0.001). Sex (female/male) was observed to have a doubted trend towards significance (HR, 0.487 [0.231-1.030]; p = 0.060).

CONCLUSIONS

PCNSTCL is generally of poor prognosis but younger age at diagnosis (<60 years) predicts a better prognosis.

Primary CNS T-cell Lymphomas: A Clinical, Morphologic, Immunophenotypic, and Molecular Analysis

Primary central nervous system (CNS) lymphomas are relatively rare with the most common subtype being diffuse large B-cell lymphoma. Primary CNS T-cell lymphomas (PCNSTL) account for <5% of CNS lymphomas. We report the clinical, morphologic, immunophenotypic, and molecular characteristics of 18 PCNSTLs. Fifteen cases were classified as peripheral T-cell lymphoma, not otherwise specified, 2 of which were of γδ T-cell derivation and 1 was TCR silent; there was 1 anaplastic large cell lymphoma, ALK-positive and 2 anaplastic large cell lymphoma, ALK-negative. Median age was 58.5 years (range, 21 to 81 y), with an M:F ratio of 11:7. Imaging results showed that 15 patients had supratentorial lesions. Regardless of subtype, necrosis and perivascular cuffing of tumor cells were frequently observed (11/18 cases). CD3 was positive in all cases but 1; 10/17 were CD8-positive, and 5/17 were CD4-positive. Most cases studied had a cytotoxic phenotype with expression of TIA1 (13/15) and granzyme-B (9/13). Polymerase chain reaction analysis of T-cell receptor γ rearrangement confirmed a T-cell clone in 14 cases with adequate DNA quality. Next-generation sequencing showed somatic mutations in 36% of cases studied; 2 had >1 mutation, and none showed overlapping mutations. These included mutations in DNMT3A, KRAS, JAK3, STAT3, STAT5B, GNB1, and TET2 genes, genes implicated previously in other T-cell neoplasms. The outcome was heterogenous; 2 patients are alive without disease, 4 are alive with disease, and 6 died of disease. In conclusion, PCNSTLs are histologically and genomically heterogenous with frequent phenotypic aberrancy and a cytotoxic phenotype in most cases.

Low grade cerebellar T-cell lymphoma: a novel response to treatment; a case report

Low-grade primary T-cell lymphoma of the central nervous system is extremely rare. We present a case developing in a previously fit young woman presenting with symptoms of raised intracranial pressure and found on CT to have a cerebellar mass. Biopsy of this lesion revealed features of non-Hodgkin's lymphoma with histochemical analysis confirming T-cell phenotype and a Ki67 proliferation index of only 1%. Contrary to the prevailing view in the literature, the patient's clinical condition deteriorated following high-dose intravenous methotrexate and improved after a short course of whole-brain radiotherapy.

Primary brain T-cell lymphoma of the lymphoblastic type presenting as altered mental status

The authors present a case of a 56-year-old man with altered mental status. Magnetic resonance imaging (MRI) of the brain revealed non-enhancing abnormalities on T2 and FLAIR imaging in the brainstem, cerebellum, and cerebrum. Immunohistochemisty demonstrated precursor T-cell lymphoblastic lymphoma. After treatment with methotrexate, he improved clinically without focal sensorimotor deficits and with improving orientation. MRI showed almost complete resolution of brainstem and cerebral lesions. To the authors’ knowledge, there are only five previous reports of primary central nervous system T-cell lymphoblastic lymphoma. Since treatable, it deserves consideration in patients with altered mental status and imaging abnormalities that include diffuse, non-enhancing changes with increased signal on T2-weighted images.

Primary T-cell lymphoma of the retina and cerebellum: immunophenotypic and gene rearrangement confirmation

PURPOSE

To document fully the first credible primary T-cell lymphoma of the retina and central nervous system in a 71-year-old man.

DESIGN

Interventional, retrospective report.

METHODS

Critical analysis of clinical history and findings, which included bilateral vitreitis with anterior chamber reaction, creamy intraretinal infiltrates, and retinal detachment; complete blood counts and other blood studies (anti-neutrophil cytoplasmic antibody [ANCA], angiotensin-converting enzyme levels, and Lyme and fluorescent treponemal antibody absorption titers); magnetic resonance imaging (MRI) scanning of the brain with total body computed tomographic and positron emission tomographic scanning; interleukin (IL) level determinations (IL-10 and IL-6); cytologic and electron microscopic evaluations; immunophenotyping of cells; and polymerase chain reaction studies for viral deoxyribonucleic acid and ribonucleic acid, and immunoglobulin heavy-chain, and T-cell receptor (TCR) gene rearrangements.

RESULTS

The first vitreous specimen was diagnosed mistakenly as cytologically reactive and contained elevated levels of IL-10 and IL-6 in a ratio of 7 to 1. T cells predominated on immunophenotypic analysis. Computed tomographic and positron emission tomographic whole body scanning showed negative results for lymphoma. An MRI scan of the brain eventually revealed a cerebellar lesion. A retinal biopsy harbored cytologically atypical pleomorphic cells that were almost all immunophenotypically T cells; polymerase chain reaction studies demonstrated a clonal TCR gene rearrangement. T-cell lymphocytes in the biopsy specimen of the cerebellum had an identical clonal TCR gene rearrangement.

CONCLUSIONS

This case unequivocally establishes that primary retinal T-cell lymphoma accompanied by central nervous system involvement can occur. Elevation in the IL-10 to IL-6 ratio in the face of inconclusive or confusing vitreous cytologic and immunophenotypic findings (a predominance of "reactive T cells with some atypicality") should lead to gene rearrangement studies on biopsies of involved tissues for the detection of T-cell clonality.

Transmission of anaplastic large cell lymphoma via organ donation after cardiac death

Recently, donation after cardiac death (DCD) has been encouraged in order to expand the donor pool. We present a case of anaplastic T-cell lymphoma transmitted to four recipients of solid organ transplants from a DCD donor suspected of having bacterial meningitis. On brain biopsy, the donor was found to have anaplastic central nervous system T-cell lymphoma, and the recipient of the donor's pancreas, liver and kidneys were found to have involvement of T-cell lymphoma. The transplanted kidneys and pancreas were excised from the respective recipients, and the kidney and pancreas recipients responded well to chemotherapy. The liver recipient underwent three cycles of chemotherapy, but later died due to complications of severe tumor burden. We recommend transplanting organs from donors with suspected bacterial meningitis only after identification of the infectious organism. In cases of lymphoma transmission, excision of the graft may be the only chance at long-term survival.

Primary meningeal lymphoma of T-cell origin: a rare presentation of primary central nervous system lymphomas

Primary meningeal lymphoma is a rare clinical entity. Central nervous system infiltration by systemic lymphoma should always be excluded. Diagnosis can be difficult, and prognosis is usually poor. Most are of B-cell origin. We present the case of a young man with a primary meningeal lymphoma of T-cell origin. He was treated with systemic chemotherapy with high-dose methotrexate and cytarabine and intraventricular chemotherapy. He had a clinical improvement and a complete remission, with a long overall survival. There is no standard treatment for this rare disease. Traditionally, treatment has been based in craniospinal radiation therapy and intrathecal chemotherapy, with poor overall results. More recently, systemic chemotherapy with high-dose methotrexate has been advocated, which could avoid the long-term toxicity of craniospinal radiation therapy, and could improve the prognosis of these patients.

Low-grade follicular lymphoma in the dura: Rare mimic of meningioma

Lymphomas rarely present as a localized mass within the dura. We report a case of a 72-year-old woman, normally fit and well, who presented with a sudden episode of grand mal seizure. Imaging studies showed an extra-axial mass arising from the dura, with radiologic features characteristic of a meningioma. The mass was surgically excised, and the histologic features were of a grade 1 follicular lymphoma. Analysis using fluorescent in situ hybridization (FISH) demonstrated t(14:18) translocation. A bone marrow aspirate showed focal infiltration of lumbar vertebra by low-grade follicular lymphoma. Intracranial meningeal involvement by non-Hodgkin lymphoma usually occurs in the form of diffuse leptomeningeal spread. It is seen in high-grade lymphomas, often in association with widespread systemic disease. The majority of cases of dural lymphomas reported in the literature have been primary mucosa-associated lymphoid tissue (MALT)-type lymphomas. Most of these presented as localized dural masses mimicking meningiomas. Low-grade follicular lymphoma, either primary or secondarily involving the dura, appears to be an exceedingly rare occurrence.

Molecular pathogenesis of primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is an aggressive form of non-Hodgkin lymphoma (NHL) typically associated with a worse prognosis than other localized extranodal lymphomas with similar histological characteristics. The defining feature of PCNSL is its confinement to the central nervous system (CNS), with proclivity for growth within the leptomeningeal as well as intraocular compartments. Primary CNS lymphoma rarely disseminates outside the CNS and accounts for less than 5% of all primary brain neoplasms. At least 95% of PCNSLs are of large B-cell histology, the most common subtype of NHL. Consistent with the trend seen in systemic NHLs, the incidence of PCNSL has markedly increased over the past three decades, both in immunocompromised and immunocompetent patients. Because PCNSL is relatively rare, the identification of molecular prognostic biomarkers and the definition of a standard therapeutic strategy have been challenging. The authors discuss the current knowledge of the molecular pathogenesis of CNS lymphomas and review the recent advances in gene expression profile analysis and identification of novel prognostic biomarkers.

Rare pathological variants and presentations of primary central nervous system lymphomas

Primary central nervous system lymphoma (PCNSL) is a rare form of primary brain neoplasm, accounting for less than 3% of all primary brain tumors. Ninety percent of cases involve a large B-cell lymphoma that presents as a homogeneously enhancing lesion or lesions, typically deep-seated in the brain parenchyma. The authors describe unusual pathological forms of PCNSLs, including low-grade, T-cell, and Burkitt types, and also rare presentations such as neurolymphomatosis and pituitary lymphomas.

Pathology of primary central nervous system lymphoma

✓ The understanding of primary central nervous system lymphoma (PCNSL) has lagged behind that of the much more common systemic, nodal lymphomas. Reasons for this include the relative rarity of PCNSL and the fact that these lesions differ in some ways from their histologically similar systemic counterparts. The purpose of this paper is twofold: first, the author provides concise descriptions of the pathological features of both common and uncommon types of PCNSL while discussing issues such as the confusion surrounding histological classification of PCNSLs, problems related to intraoperative diagnosis, and the appropriate diagnostic work up. Second, the author discusses a small number of molecular studies to demonstrate the great promise they offer. Such studies have already clarified some issues, including the category of lymphocyte from which the majority of PCNSLs are derived. Hopefully in the future these studies will help guide treatment decisions.

Pathology and genetics of primary central nervous system and intraocular lymphoma

Ongoing studies based on gene expression profile analysis using microarrays have provided preliminary evidence for significant molecular distinctions between primary central nervous system lymphoma (PCNSL) and nodal lymphomas of the large B-cell type. The application of array-based comparative genomic hybridization techniques attempts to identify genomic distinctions between PCNSL and nodal lymphomas and to identify the molecular markers that relate to prognosis. It is possible that insights gained from these studies will facilitate the development of targeted therapies, which address the fundamental genetic mutations that drive PCNSL and intraocular lymphoma growth.

Unusual Variants of Primary Central Nervous System Lymphoma

Rare variants of primary central nervous system lymphoma (PCNSL) include unusual sites of presentation (eg, neurolymphomatosis and primary leptomeningeal lymphoma) and uncommon pathologic entities. Neurolymphomatosis involves peripheral nerves and nerve roots in addition to systemic and central nervous system (CNS) sites. Diagnosis requires a high index of suspicion, and treatment incorporates the principles of therapy for systemic and CNS lymphoma. Primary leptomeningeal lymphoma can present with symptoms of raised intracranial pressure or cranial or spinal polyradiculopathies. Diagnosis can be made by examining cerebrospinal fluid and incorporating immunophenotyping and molecular pathology techniques. Treatment options include irradiation and intrathecal or systemic chemotherapy. The features of PCNSL of T-cell origin and indolent B-cell PCNSL also are discussed.

Primary CNS lymphoma of T-cell origin: a descriptive analysis from the international primary CNS lymphoma collaborative group

PURPOSE

To describe the demographic and tumor related characteristics and outcomes for patients with primary T-cell CNS lymphoma (TPCNSL).

PATIENTS AND METHODS

A retrospective series of patients with TPCNSL was compiled from twelve cancer centers in seven countries.

RESULTS

We identified 45 patients with a median age of 60 years (range, 3 to 84 years). Twenty (44%) had Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1. Twenty-six (58%) had involvement of a cerebral hemisphere and sixteen (36%) had lesions of deeper sites in the brain. Serum lactate dehydrogenase was elevated in 7 (32%) of 22 patients, and CSF protein was elevated in 19 of 24 patients (79%) with available data. The median disease-specific survival (DSS) was 25 months (95% CI, 11 to 38 months). The 2- and 5-year DSS were 51% (95% CI, 35% to 66%) and 17% (95% CI, 6% to 34%), respectively. Univariate and multivariate analyses were conducted for age (</= 60 v > 60 years), PS (0 or 1 v 2, 3, or 4), involvement of deep structures of the CNS (no v yes), and methotrexate (MTX) use in the primary treatment (yes v no). Only PS and MTX use were significantly associated with better outcome with hazard ratios of 0.2 (95% CI, 0.1 to 0.4) and 0.4 (95% CI, 0.2 to 0.8), respectively.

CONCLUSION

This is the largest series ever assembled of TPCNSL. The presentation and outcome appear similar to that of B cell PCNSL. PS 0 or 1 and administration of MTX are associated with better survival.

Low-grade primary central nervous system lymphoma in immunocompetent patients

Primary central nervous system lymphomas (PCNSL) are usually diffuse large B-cell non-Hodgkin's lymphomas (NHL). Here we characterize the clinical presentation, course and outcome of patients with low-grade PCNSL. Records of 332 patients screened for inclusion in three multicentre prospective trials were reviewed. Ten patients (3%) with a median age of 59 years and a median Karnofsky performance status of 70% were identified. Seven patients had B-cell and three had T-cell lymphoma. The median growth fraction was 4%. The radiological morphology was unusual for PCNSL in eight patients. Three patients underwent complete tumour resection, combined with chemotherapy in one patient and with chemotherapy plus local radiotherapy in another. Four patients received chemotherapy and three received chemotherapy plus whole-brain irradiation, resulting in four complete remissions, two no-change situations and one progressive disease. Patients had an overall survival (OAS) of 2-58+ months with a 2-year OAS of 67%. Low-grade PCNSL may differ from classical high-grade PCNSL in its clinical features and radiological morphology. The clinical course may be variable and frequently more indolent than in classical PCNSL.

Primary central nervous system lymphoma in Korea: comparison of B- and T-cell lymphomas

The great majority of primary central nervous system lymphoma (PCNSL) is known to be of B-lineage, with T-cell PCNSL (T-PCNSL) accounting for <5%. We report an unusually high incidence of T-cell lymphoma among the PCNSLs originated in a large general-care hospital in the metropolitan Seoul area. PCNSLs (n = 42) accrued from April 1995 through June 2001 were reviewed for histologic and clinical features, and immunohistochemical staining was done for CD3, CD20, CD4, CD8, Bcl-6, and CD10. Clonal rearrangements of the TCR-gamma and IgH genes were studied with semi-nested PCR in all seven cases of T-PCNSL and seven of 35 B-cell PCNSL (B-PCNSL). Formalin-fixed, paraffin-embedded specimens were used in all these studies. By immunohistochemical staining and molecular studies, seven cases (16.7%) were diagnosed as T-PCNSL, each displaying clonal rearrangement of the TCR-gamma gene, and 35 (83.3%) as B-PCNSL. Radiologically, T-PCNSL was significantly correlated with the superficial and subcortical lobar location (p <0.001), solitary mass formation (p = 0.001), presence of rim enhancement (p <0.001), and peritumoral edema (p = 0.029). Involvement of cerebrospinal fluid was observed only in B-PCNSL (n = 17) but not in T-PCNSL (p = 0.010). Histologically, T-PCNSL was characterized by a population of mixed predominantly small- and occasionally medium-sized cells (p <0.001), which were loosely scattered without forming a solid mass (p = 0.024), and perivascular infiltration was frequent (p = 0.007), in contrast to predominantly large cells of B-PCNSL, i.e., diffuse large B-cell lymphoma (DLBCL), in which the cells tended to aggregate to form monomorphous sheets (p = 0.024). In T-PCNSL, staining for CD8 was positive in five, including one with coexpression of CD4, and two were negative for CD4 and CD8. Of 24 DLBCLs tested, the pattern of Bcl-6+ tumor cells was diffusely dense, similar to that of the germinal center in nine cases (37.5%), with coexpression of CD10 in three of the nine cases. T-PCNSL accounted for 16.7% of the PCNSLs; thus, in Korea it may not be as rare as previously known. The T-PCNSL presented with certain clinical and pathologic features that were distinct from B-PCNSL and displayed preponderance of CD8 expression. DLBCL of the germinal center B-cell derivation defined by bcl-6 expression comprised 37.5% of DLBCL of the brain.

Diagnostic advances and new trends for the treatment of primary central nervous system lymphoma

Primary central nervous system lymphoma (PCNSL) is a rare non-Hodgkin's lymphoma arising in the brain. Recent increase in its incidence has been noted both in immunocompetent individuals and patients with immunodeficiency. This review will focus on the epidemiology, pathogenesis, diagnosis and treatment of this aggressive extranodal lymphoma in immunocompetent patients. Stereotactic biopsy is usually required for diagnosis, while molecular biology and/or cytofluorimetric analysis may confirm the presence of clonal proliferation in the cerebrospinal fluid (CSF). Methotrexate-based chemotherapy plus whole-brain radiotherapy are the standard treatment for PCNSL and achieve a high rate of complete remissions (CR), but long-term neurotoxicity may heavily compromise the patient's quality of life. The metabolic rate of controversial gadolinium-enhancing lesions on magnetic resonance (MR) scans may be assessed with positron emission tomography (PET), which discriminates radiation necrosis from true recurrence. Withholding radiotherapy in patients achieving CR after first-line chemotherapy is a new and interesting treatment option, while the role of high-dose chemotherapy with stem cell rescue is still uncertain.

Primary central nervous system lymphomas: incidence and survival in the Southern and Eastern Netherlands

BACKGROUND

An excessive increase in the incidence of primary central nervous system lymphoma (PCNSL) has been reported since the mid-1980s in the U.S. and U.K. Clinical studies have shown that radiotherapy and chemotherapy may prolong survival. In the current study, the authors describe the incidence, treatment, and survival of an unselected group of patients with PCNSL in the southern and eastern Netherlands.

METHODS

Data regarding patients diagnosed between 1989-1994 were obtained from 4 population-based regional cancer registries in the southern and eastern Netherlands (n = 86) and the Eindhoven Cancer Registry for 1980-1988 (n = 6). Lymphomas were registered as PCNSL when a tissue diagnosis of CNS lymphoma was established for a patient with neurologic symptoms (i.e., lymphomas were not necessarily restricted to the CNS at the time of diagnosis). Only patients diagnosed during their lifetime with Stage I disease, Stage "IV" disease (i.e., diffuse CNS lymphoma), or disease of unknown stage were included (63 patients, 8 patients, and 15 patients, respectively, between 1989-1994). For 80 patients (93%) follow-up was complete until January 1, 1997.

RESULTS

Between 1989-1994, an average World Standardized Rate of 2.3 cases and 1.7 cases per 1 million person-years, respectively, was reported for males and females. The median age of the patients at the time of diagnosis was 62 years, and was 66 years for patients with an unknown disease stage. In the area of the Eindhoven Cancer Registry the occurrence of PCNSL more than doubled from < 2% of all histologically confirmed primary CNS malignancies diagnosed between 1980-1985 to approximately 4% of cases diagnosed between 1986-1994. The median survival of all the patients was 4.1 months; the median survival was 5.8 months for patients with limited (Stage I and Stage IV) disease and was 0.6 months for patients with an unknown stage of disease. Approximately 65% of the patients with limited disease received radiotherapy and approximately 35% of such patients received chemotherapy. Furthermore, chemotherapy was given more often to patients age < 60 years who tended to have a slightly better survival than patients age > or = 60 years.

CONCLUSIONS

The increase in the incidence of PCNSL in the 1980s may be explained in large part by changes in diagnostics and registration. The relatively high incidence and low survival rate of PCNSL in the southern and eastern Netherlands reported in the 1990s may be due in part to the inclusion of patients with systemic lymphoma and immunodeficiency disorders. However, a significant improvement in the prognosis of patients with PCNSL in the southern and eastern Netherlands diagnosed in the 1990s is unlikely.

Spontaneous remission of primary central nervous system lymphoma: report of 3 cases and discussion of pathophysiology

Primary central nervous system lymphoma (PCNSL) is a relatively uncommon disease in which spontaneous remission is exceedingly rare. We are reporting three cases of primary CNS lymphoma with spontaneous regression in two to eight weeks, from the time of the initial diagnosis. The remission lasted for four years in the first case, two years in the second, and one year in the third case. Tissue diagnosis was made in the first two cases after relapse, and in the third case a biopsy was done at the initial presentation. The literature and the possible pathophysiological mechanisms of this interesting phenomenon are discussed.