Characteristics of Central Nervous System (CNS) Involvement in Children With Non-Hodgkin's Lymphoma (NHL) and the Diagnostic Value of CSF Flow Cytometry in CNS Positive Disease.

OBJECTIVE: To investigate the characteristics of central nervous system (CNS) involvement in children with non-Hodgkin's lymphoma (NHL) and the value of flow cytometry (FC) in the diagnosis of CNS disease in pediatric NHL. METHODS: The data of 56 newly diagnosed pediatric NHL patients with CNS involvement (CNS+/mass, CNS+/palsy, CNS+/CSF) were analyzed. The proportions and formats of CNS disease in different pathological types were compared. In addition, FC and conventional cytology (CC) of cerebrospinal fluid (CSF) were carried out in 383 newly diagnosed NHL cases. RESULTS: A total of 383 children with NHL were enrolled. Among these patients, 56 (14.6%) were diagnosed with positive CNS involvement (CNS+), 33 had bulky disease (tumor diameter >10 cm), 32 had bone marrow invasion, 32 had lactate dehydrogenase levels >1000 U/L, and 25 had invasion of more than 4 organs at the time of diagnosis. There were 14 patients with T lymphoblastic lymphoma (T-LBL), 9 with B lymphoblastic lymphoma (B-LBL), 26 with Burkitt's lymphoma (BL), and 2 with Epstein-Barr virus-positive diffuse large B cell lymphoma (EBV + DLBCL). Among the 56 CNS+ patients, 35 were CSF-positive (CSF+); there were 2 patients who were CSF+ via CC detection and 35 who were CSF+ via FC detection. The difference between CC and FC was statistically significant (P < 0.01). In the T-LBL group, 14 patients were CNS+/CSF, and in the B-LBL group, 8 were CNS+/mass. In the BL group, 22 patients were CNS+/mass and 15 were CNS+/CSF. In the anaplastic large-cell lymphoma group, 5 patients were CNS+/mass. Nine of the 56 CNS+ patients had events. The 2-year overall survival rate was 87% ± 0.046%, and the 2-year event-free survival rate was 76.2% ± 0.07%. CONCLUSION: CNS+ diagnoses were more common in pediatric NHL patients with bulky disease and/or bone marrow involvement and/or involvement of more than 4 organs at the time of diagnosis, and they were also common in the EBV + DLBCL and BL groups. FC of CSF showed important clinical significance in the diagnosis of CNS disease in pediatric NHL patients, and it can be used to significantly improve the CNS+ detection rate.

A rapid genotyping panel for detection of primary central nervous system lymphoma.

Diagnosing primary central nervous system lymphoma (PCNSL) frequently requires neurosurgical biopsy due to nonspecific radiologic features and the low yield of cerebrospinal fluid (CSF) studies. We characterized the clinical evaluation of suspected PCNSL (N = 1007 patients) and designed a rapid multiplexed genotyping assay for MYD88, TERT promoter, IDH1/2, H3F3A, and BRAF mutations to facilitate the diagnosis of PCNSL from CSF and detect other neoplasms in the differential diagnosis. Among 159 patients with confirmed PCNSL, the median time to secure a diagnosis of PCNSL was 10 days, with a range of 0 to 617 days. Permanent histopathology confirmed PCNSL in 142 of 152 biopsies (93.4%), whereas CSF analyses were diagnostic in only 15/113 samplings (13.3%). Among 86 archived clinical specimens, our targeted genotyping assay accurately detected hematologic malignancies with 57.6% sensitivity and 100% specificity (95% confidence interval [CI]: 44.1% to 70.4% and 87.2% to 100%, respectively). MYD88 and TERT promoter mutations were prospectively identified in DNA extracts of CSF obtained from patients with PCNSL and glioblastoma, respectively, within 80 minutes. Across 132 specimens, hallmark mutations indicating the presence of malignancy were detected with 65.8% sensitivity and 100% specificity (95% CI: 56.2%-74.5% and 83.9%-100%, respectively). This targeted genotyping approach offers a rapid, scalable adjunct to reduce diagnostic and treatment delays in PCNSL.

Multi-marker algorithms based on CXCL13, IL-10, sIL-2 receptor, and ß2-microglobulin in cerebrospinal fluid to diagnose CNS lymphoma.

Tumor biopsy is essential for the definitive diagnosis of central nervous system (CNS) lymphoma. However, the biopsy procedure carries the risk of complications such as bleeding, convulsions, and infection. Cerebrospinal fluid (CSF) ß2-microglobulin (ß2-MG), soluble IL-2 receptor (sIL-2R), and interleukin-10 (IL-10) are known to be useful diagnostic biomarkers for CNS lymphoma. The C-X-C motif chemokine ligand 13 (CXCL13) was recently reported to be another useful biomarker for CNS lymphoma. The purpose of this study is to establish a diagnostic algorithm that can avoid biopsy by combining these diagnostic biomarkers. In the first, we conducted a case-control study (n = 248) demonstrating that the CSF CXCL13 concentration was significantly increased in CNS lymphoma patients compared with various other brain diseases (AUC = 0.981). We established a multi-marker diagnostic model using CSF CXCL13, IL-10, ß2-MG, and sIL-2R from the results of the case-control study and then applied the model to a prospective study (n = 104) to evaluate its utility. The multi-marker diagnostic algorithms had excellent diagnostic performance: the sensitivity, specificity, positive predictive value, and negative predictive value were 97%, 97%, 94%, and 99%, respectively. In addition, CSF CXCL13 was a prognostic biomarker for CNS lymphoma patients. Our study suggests that multi-marker algorithms are important diagnostic tools for patients with CNS lymphoma.

A Retrospective Analysis of Invasive Fungal Diseases (IFD) of the Central Nervous System in Children With Lymphoid Malignancies.

BACKGROUND: Outcomes of childhood hematolymphoid malignancies have improved several fold because of immunosuppressive chemotherapy and broad-spectrum antibiotics for managing febrile neutropenia. An apparent trade-off has been an increase in invasive fungal disease (IFD), affecting multiple organs. We report the diagnostic and therapeutic challenges in 8 children with lymphoid cancers who developed intracranial (IC) fungal abscesses between 2010 and 2017. METHODS: Children below 15 years of age undergoing treatment for leukemia/lymphoma with clinicoradiologic and microbiologic evidence of IC fungal abscess were included. Demographic details, clinical profile, and management were retrospectively audited. Treatment was guided by European Organization for Research and Treatment of Cancer/Mycoses Study Group (EORTC/MSG) definitions for IFD with therapeutic drug monitoring (TDM)-directed azole dosing, and surgical intervention. RESULTS: Eight patients (4 B-cell acute lymphoblastic leukemia, 2 relapsed B-cell acute lymphoblastic leukemia, and 2 non-Hodgkin lymphoma) were eligible for analysis. Proven, probable, and possible IFDs were seen in 2 (25%), 4 (50%), and 2 (25%) patients, respectively. Proven IFDs were invasive mucormycosis with remaining having mold infections. Cerebrospinal fluid galactomannan was positive in all 4 patients in whom it was tested. TDM was possible in 5/8 (63%) patients. Antifungal therapy was given for a median period of 4.2 months with 5 (63%) patients having complete resolution. Three (37%) patients expired, of which 2 were attributable to IFDs. CONCLUSIONS: IC fungal abscesses in children can cause significant morbidity and mortality in children with hematolymphoid cancers. Evaluation of cerebrospinal fluid galactomannan may help in early diagnosis and therapy. Prolonged antifungal therapy steered by TDM can help achieve resolution in some cases.

Supervivencia de pacientes con linfoma no-Hodgkin y síntomas neurológicos según inmunofenotipo del líquido cefalorraquídeo / Survival in non-Hodgkin´s lymphoma patients with neurological symptoms according to the cerebrospinal fluid immunophenotype

Introducción: Los linfomas no-Hodgkin pueden infiltrar el sistema nervioso central y producir síntomas neurológicos, lo cual incrementa la mortalidad. El diagnóstico de esta infiltración se puede realizar mediante el estudio del líquido cefalorraquídeo por la técnica de citometría de flujo, con una mayor sensibilidad que la citología convencional. Objetivo: Estimar la supervivencia global de pacientes con Linfoma no-Hodgkin y síntomas neurológicos según el inmunofenotipo celular del líquido cefalorraquídeo. Métodos: Se realizó un estudio analítico y prospectivo en 15 pacientes con diagnóstico confirmado de linfoma no-Hodgkin y síntomas neurológicos, con citología negativa del líquido cefalorraquídeo, tratados en el servicio de oncología del Instituto Nacional de Oncología y Radiobiología, durante los años 2017 y 2018. El inmunofenotipo fue caracterizado mediante citometría de flujo multiparamétrica. Resultados: El 60,0 por ciento de los pacientes fue del sexo femenino y el 53,4 por ciento mayor de 60 años. Hubo una mortalidad del 26,7 por ciento. Se realizaron 17 inmunofenotipos, el 58,9 por ciento fue normal, el 23,4 por ciento reactivo y el 17,7 por ciento sospechoso de malignidad. La supervivencia global fue mayor en pacientes con líquido cefalorraquídeo con inmunofenotipo normal (HR. 0.04). Conclusiones: La citometría de flujo pudo discriminar células sospechosas de malignidad, en pacientes cuyas citologías fueron negativas. La presencia en el líquido cefalorraquídeo de células atípicas, de pleocitosis y de un índice de linfocito-monocito alto se asoció con una supervivencia global menor(AU)

Introduction: When non-Hodgkin lymphomas infiltrate the central nervous system increases mortality. The diagnosis of this infiltration can be made by the study of cerebrospinal fluid using flow cytometry, with a higher sensitivity than conventional cytology. Objective: To estimate the relationship between the cellular immunophenotype of the cerebrospinal fluid and the overall survival of patients with non-Hodgkin lymphoma and neurological symptoms. Methods: An analytical and prospective study was conducted in 15 patients with confirmed diagnosis of non-Hodgkin lymphoma and neurological symptoms, with negative cytology of the cerebrospinal fluid. Patients cared at Oncology Department of the National Institute of Oncology and Radiobiology, during the years 2017-2018. The immunophenotype was characterized by multiparametric flow cytometry. Results: 60.0 percent of the patients was female and 53.4 percent older than 60 years. There was an overall mortality of 26.7 percent 17 immunophenotypes were found, 58.9 percent of them was normal, 23.4 percent reactive and 17.7 percent suspected of malignancy. Overall survival advantage was obtained in patients with cerebrospinal fluid with normal immunophenotype (HR 0.04). Conclusions: Flow cytometry could discriminate cells suspected of malignancy, in patients whose cytologies were negative. The presence in the cerebrospinal fluid of atypical cells, pleocytosis and a high lymphocyte-monocyte index were associated with a lower overall survival(AU)

Optimization of CSF biological investigations for CNS lymphoma diagnosis.

Diagnosis of lymphoma leptomeningeal dissemination is challenging and relies on a wide array of methods. So far, no consensus biological guidelines are available. This increases the chance of intra- and interpractice variations, despite the shared concern to perform the minimum amount of tests while preserving clinically relevant results.We evaluated a training cohort of 371 cerebrospinal fluid (CSF) samples from patients with putative lymphomatous central nervous system (CNS) localization using conventional cytology (CC), flow cytometry (FCM), molecular clonality assesment by PCR and cytokine quantification (CQ). This led us to propose a biological algorithm, which was then verified on a validation cohort of 197 samples. The samples were classified according to the clinical context and the results of each technique were compared. Using all four techniques was not useful for exclusion diagnosis of CNS lymphoma (CNSL), but they proved complementary for cases with suspected CNSL. This was particularly true for CQ in primary CNSL. Overall, diagnosis can be obtained with a two-step approach. The first step comprises CC and FCM, as results are available quickly and FCM is a sensitive method. Both PCR and CQ can be postponed and performed in a second step, depending on the results from the first step and the clinical context.The proposed algorithm missed none of the CNSL samples of the validation cohort. Moreover, applying this algorithm would have spared 30% of PCR tests and 20% of CQ over a one-year period, without compromising clinical management.

Comparison between cytospin and liquid-based cytology in cerebrospinal fluid diagnosis of neoplastic diseases: A single institution experience.

OBJECTIVE: The current tools available for detecting malignant neoplasms in the cerebrospinal fluid (CSF) are neurological examination, followed by neuroimaging, cytology and molecular techniques. To highlight the role of cytology the diagnosis of metastatic tumours in CSF samples, we present our experience using cytospin and ThinPrep liquid-based cytology. METHODS: A retrospective analysis was conducted using the pathological records of 8181 cytological specimens of CSF, which were diagnosed over a 17-year period. Between 2000 and 2014, a total of 6994 CSF samples were processed using cytospin method and 1187 specimens were examined using ThinPrep method in the period between 2015 and 2017. RESULTS: The most frequent metastatic neoplasm of the first period was non-Hodgkin lymphoma; in the second period the commonest malignancy found was brain tumour (glioblastoma and medulloblastoma). The samples processed by cytospin revealed cytolysis and haemorrhage, while the cases processed by ThinPrep had a clear background. Ten false-positive cases belonging to the suspicious category were processed by cytospin, while there was only one false positive case in the group processed by ThinPrep. The positive predictive value was 95% in cytospin and 100% in Thin Prep with comparable sensitivity, specificity, diagnostic accuracy and negative predictive values. CONCLUSIONS: CSF cytology is a reliable technique for identifying malignancy in CSF. ThinPrep technology can be applied with good results in terms of clear background, cell enrichment, better nuclear details and high cellularity per slide.

Spinal cord involvement in primary CNS lymphoma.

LETM is a common syndrome and the diagnosis of CNS lymphoma is not usually considered in the list of differentials. Primary CNS lymphoma can present as longitudinally extensive transverse myelopathy. Failure to suspect and evaluate leads to delay in diagnosis and treatment. PCNSL may be non contrast enhancing on gadolinium enhanced MRI. CSF analysis should be done preferably before starting corticosteroids as it is usual practice in treatment of transverse myelitis, as steroids may lead to transient improvement and mask the correct diagnosis. Repeated CSF examinations may be needed to clinch the diagnosis.

Soluble TACI and soluble BCMA as biomarkers in primary central nervous system lymphoma.

BACKGROUND: B-cell survival is regulated through interactions of B-cell-activating factor and a proliferation-inducing ligand with their receptors transmembrane activator and CAML interactor (TACI) and B-cell maturation antigen (BCMA). We evaluated the diagnostic potential of soluble TACI (sTACI) and soluble BCMA (sBCMA) in CSF and serum as biomarkers in primary CNS lymphoma (PCNSL). METHODS: CSF (n = 176) and serum samples (n = 105) from patients with clinically or radiologically suspected PCNSL as well as from control patients were collected prospectively. Levels of sTACI and sBCMA were analyzed by enzyme-linked immunosorbent assay. Additionally, in patients with PCNSL, CSF was analyzed during disease course (time of diagnosis, n = 26; relapse, n = 10; remission, n = 14), and in 2 patients long-term longitudinal analysis was performed. RESULTS: Soluble TACI and sBCMA are significantly increased in patients with PCNSL (sTACI, median: 445 pg/mL; sBCMA, median: 760 pg/mL) compared with control patients (sTACI, median: 0 pg/mL; sBCMA, median: 290 pg/mL). At a cutoff value of 68.4 pg/mL, sTACI shows high sensitivity (87.9%) and specificity (88.3%) for the diagnosis of active PCNSL. Soluble BCMA is less sensitive (72.7%) and specific (71.8%) (cutoff: 460 pg/mL). When both markers are combined, specificity increases, however, at the cost of a lower sensitivity. In serum, both sTACI and sBCMA are not increased in PCNSL patients. Both soluble receptors correlate with clinical course and therapy response. CONCLUSIONS: Our results suggest that sTACI and sBCMA in the CSF are promising new biomarkers for diagnosis and therapy monitoring in PCNSL. However, our findings need to be validated in an independent cohort.

Final results of a multicenter trial addressing role of CSF flow cytometric analysis in NHL patients at high risk for CNS dissemination.

This prospective study compared diagnostic and prognostic value of conventional cytologic (CC) examination and flow cytometry (FCM) of baseline samples of cerebrospinal fluid (CSF) in 174 patients with newly diagnosed aggressive non-Hodgkin lymphoma (NHL). FCM detected a neoplastic population in the CSF of 18 of 174 patients (10%), CC only in 7 (4%; P < .001); 11 patients (14%) were discordant (FCM(+)/CC(-)). At a median follow-up of 46 months, there were 64 systemic progressions and 10 CNS relapses, including 2 patients with both systemic and CNS relapses. Two-year progression-free and overall survival were significantly higher in patients with FCM(-) CSF (62% and 72%) compared with those FCM(+) CSF (39% and 50%, respectively), with a 2-year CNS relapse cumulative incidence of 3% (95% confidence interval [CI], 0-7) versus 17% (95% CI, 0-34; P = .004), respectively. The risk of CNS progression was significantly higher in FMC(+)/CC(-) versus FCM(-)/CC(-) patients (hazard ratio = 8.16, 95% CI, 1.45-46). In conclusion, FCM positivity in the CSF of patients with high-risk NHL is associated with a significantly higher CNS relapse risk and poorer outcome. The combination of IV drugs with a higher CNS bioavailability and intrathecal chemotherapy is advisable to prevent CNS relapses in FCM(+) patients.

Flow cytometric detection of liposomal cytarabine in cerebrospinal fluid of patients treated with intrathecal chemotherapy.

We report the unusual flow cytometric detection of liposomes in the cerebrospinal fluid of patients with aggressive non-Hodgkin's lymphoma and acute myeloid leukemia, treated with intrathecal liposomal cytarabine.

Isolated leptomeningeal infiltration of a primary CNS B-cell lymphoma diagnosed by flow cytometry and confirmed by necropsy.

BACKGROUND: The diagnosis of the isolated leptomeningeal involvement of a primary central nervous system B-cell lymphoma without parenchyma lesions may be difficult. Patients with leptomeningeal meningeosis lymphomatosa can present with various neurologic deficits. AIMS OF THE STUDY: To demonstrate the impact of cerebrospinal fluid (CSF) flow cytometry in the diagnosis of an isolated leptomeningeal manifestation of B-cell lymphoma by presenting an interesting case report. METHODS: Flow cytometric analysis of B-cell monoclonality of the CSF was performed as complementary diagnostic procedure in addition to CSF cytology. Final diagnosis was confirmed by necropsy. RESULTS: We suspected isolated leptomeningeal manifestation of B-cell lymphoma with palsy of the VI and VII cranial nerves in a 79-year-old male, because of mononuclear pleocytosis in CSF. Interestingly, the decisive diagnostic hint was given by implementation of flow cytometry of the CSF. Diagnosis was confirmed by postmortem autopsy. CONCLUSION: Our case shows that flow cytometry of the CSF in addition to conventional CSF cytology has the potential to accelerate diagnosis of lymphomeningeal infiltration of B-cell lymphoma.

Cerebrospinal fluid interleukin-10 is a potentially useful biomarker in immunocompetent primary central nervous system lymphoma (PCNSL).

The diagnosis of primary central nervous system lymphoma (PCNSL) by radiographical examination is often difficult because of its similarity to other brain tumors. To test whether interleukin-10 (IL-10) and IL-6 can be used to distinguish PCNSL from other brain tumors that are radiographically similar, cerebrospinal fluid (CSF) levels of IL-10 and IL-6 were measured in 66 patients with intracranial tumors (PCNSLs: 26 cases; other brain tumors: 40 cases). In the patients with PCNSLs, the median CSF levels of IL-10 and IL-6 were 27 pg/mL and 5.4 pg/mL, respectively. The CSF IL-10 and IL-6 levels were significantly higher in PCNSLs than in the other brain tumors. To validate the diagnostic value of CSF IL-10 in PCNSL, we prospectively examined 24 patients with brain lesions that were suspected to be PCNSL. We observed that the CSF IL-10 levels were significantly higher in PCNSLs than in other brain tumors. At an IL-10 cutoff level of 9.5 pg/mL, the sensitivity and specificity were 71.0% and 100%, respectively. After therapy, the CSF IL-10 levels were decreased in all patients and were increased at relapse in most of these patients. Immunohistochemically, all PCNSLs, except for 1 unclassified PCNSL, expressed both IL-10 and IL-10 receptor-A. In the patients with high CSF IL-10, IL-10 expression levels in tumor were relatively higher, compared with low CSF IL-10; however, there was no significant difference between these groups. In addition, elevated CSF level of IL-10 was significantly associated with having a shorter progression-free survival (hazard ratio, 3.37; 95% confidence interval, 0.985-11.528; log-rank, P= .038). These results indicate that the CSF level of IL-10 may be a useful diagnostic and prognostic biomarker in patients with PCNSLs.

CSF cytology--the ongoing dilemma to distinguish neoplastic and inflammatory lymphocytes.

To evaluate different morphological criteria for the distinction between inflammatory and neoplastic lymphocytes in the cerebrospinal fluid (CSF). Forty-two cytospin preparations of CSF from patients with confirmed CSF involvement by aggressive B-cell lymphoma or acute leukemia were compared with 26 samples of inflammatory diseases. CSF cytology was analyzed morphologically for preselected parameters of cell, cytoplasm and nucleic appearance, and the presence of mitoses or apoptoses. None of the evaluated parameters sharply discerns neoplastic and inflammatory changes. However, neoplastic cells were significantly larger. Moreover, irregular shape and pointed borders of the cytoplasm, and deep notches in the nucleus were significantly more frequent in neoplastic than in inflammatory lymphocytes. No single parameter is sufficient to detect neoplastic lymphocytes. Considering a combination of cell size and irregular shape of cell and nucleus, however, may improve the diagnostic accuracy of CSF dissemination by aggressive hematological malignancies.

Cerebral low-grade lymphoma and light chain deposition disease: exceedingly high IgG levels in the cerebrospinal fluid as a diagnostic clue.

Herein, we report the case of a 72-year-old male with an exceedingly rare manifestation of a low-grade lymphoma in the brain associated with light chain deposition disease (LCDD). The patient presented with epileptic seizures. Magnetic resonance imaging (MRI) of the brain revealed multiple hyperintense lesions in the right parietal lobe that were suspicious of vasculitis, low-grade glioma, or neurosarcoidosis. In the cerebrospinal fluid (CSF), but not in the serum, highly elevated IgG was found. A stereotactic biopsy of one cerebral lesion was performed. Histopathology revealed a low grade lymphoplasmacytic B-cell lymphoma with light chain deposition disease (LCDD). Bone marrow biopsy and laboratory workup did not show any systemic involvement. LCDD exclusively affecting the brain is an exceedingly rare finding. It can be associated with low-grade B-cell lymphoma. This is the first report of LCDD exclusively affecting the brain in an elderly patient. Compared with the two younger patients previously reported, the course of the disease was of a slow-evolving nature. In constellations of highly elevated IgG in CSF and multiple white matter lesions, LCDD should be considered as underlying pathology.

Clinical significance of occult cerebrospinal fluid involvement assessed by flow cytometry in non-Hodgkin's lymphoma patients at high risk of central nervous system disease in the rituximab era.

BACKGROUND AND AIM: Flow cytometry (FCM) analysis of cerebrospinal fluid (CSF) is more sensitive than conventional cytology (CC) for diagnosis of lymphomatous meningeosis, but the clinical significance of occult central nervous system (CNS) disease (positive FCM with negative CC) remains unknown. PATIENTS AND METHODS: CSF samples from 105 patients with newly diagnosed aggressive lymphomas at high risk of CNS involvement were prospectively studied by both CC and FCM, and results were correlated with cumulative incidence of CNS relapse and overall survival (OS). Patients were divided into three groups: 1) patients without CNS involvement (CC-/FCM-; n=83); 2) individuals with occult CNS disease (FCM+/CC-; n=15); and 3) cases with CNS disease (CC+/FCM+; n=7). RESULTS: Six cases showed CNS relapse or progression: two in Group 1 (2.4%), two in Group 2 (13%) and two in Group 3 (28.5%) (Group 2 vs. 1, P=0.04; Group 3 vs. 1, P<0.001). Patients from Groups 2 (P=0.05) and 3 (P<0.001) also showed a higher cumulative incidence of CNS relapse than those from Group 1. Significant differences were observed in OS between FCM-/CC- and FCM+/CC+ cases (P=0.02), while patients with occult CNS disease (FCM+/CC-) displayed intermediate OS rates, although differences did not reach statistical significance. CONCLUSIONS: The presence of occult CNS involvement at diagnosis in patients with NHL at high risk of CNS disease is associated with a higher probability of CNS relapse.

Diagnostic tools for neoplastic meningitis: detecting disease, identifying patient risk, and determining benefit of treatment.

Three methods are routinely used to diagnose neoplastic meningitis (NM): clinical signs and symptoms, cerebrospinal fluid (CSF) cytology, and magnetic resonance imaging (MRI) of the brain and spine. Clinical manifestations are often subtle or may be ascribed to other cancer complications, eg, treatment-related disorders or brain parenchymal metastases. CSF cytology has a high specificity (>95%), but its sensitivity is generally less than 50%. MRI sensitivity and specificity vary with the type of primary cancer; overall, MRI findings consistent with leptomeningeal disease are detected in fewer than 50% of NM patients. While most clinicians evaluate CSF cytology along with MRI and the clinical examination, underdiagnosis is a major problem, since many patients are both cytologically and radiographically negative. Failure to consider NM in the differential diagnosis magnifies the problem of underdiagnosis. CSF flow cytometry is particularly promising for evaluating NM from hematologic cancers, with a diagnostic sensitivity many fold greater than conventional cytology. Research has focused on identifying biochemical markers of tumor cells in the CSF. For example, molecules involved in CNS penetration (eg, matrix metalloproteinases and cathepsins), tumor cell tropism (eg, chemokines CXCL8 and CCL18), and angiogenesis (eg, vascular endothelial growth factor) are elevated in the CSF of patients with NM. Evidence that some tumor types are more likely to infiltrate the CNS also has stimulated research into primary tumor markers predictive of CNS metastases. At present, there is no tumor marker or patient characteristic that reliably predicts the development of NM, and diagnosis still relies on suggestive signs and symptoms, positive CSF cytology, or a consistent MRI-all late manifestations of NM. Until techniques capable of detecting NM early are developed, increased awareness of the disease and standardized evaluation are likely to have the greatest impact on improving diagnosis and implementing earlier treatment.