Cerebrospinal fluid (CSF) infiltration can be identified at diagnosis and during the course of many hematopoietic malignancies, mainly acute leukemia and aggressive non-Hodgking lymphomas (NHL). The accurate diagnosis of central nervous system (CNS) infiltration allows patients with infiltrated CSF to be properly treated, avoiding the use of unnecessary CNS therapy for patients who do not have compromised CSF. Cytomorphology is the classic method for diagnosing CSF neoplastic infiltration, but it presents variability in sensitivity and specificity according to the experience of the morphologist and cell abnormalities resulting from sample preparation. Currently, multiparametric flow cytometry (MFC) has great sensitivity and specificity to detect cells of hematopoietic neoplasms in the CSF. This is a retrospective study to assess the frequency of CSF infiltration in a cohort of patients with hematologic malignancies treated at our institution.

to evaluate the casuistry and frequency of CSF infiltration by hematologic neoplasms diagnosed by immunophenotyping in our institution.

the results of CSF immunophenotyping were collected using the flow cytometry laboratory database. Assess period: from March 2008 to June 2021. Patients were grouped by type of disease and the frequency with which each one was represented in the cohort was verified.

a total of 1572 CSF samples were analyzed by the laboratory during the study period. The frequency of diagnoses of patients whose samples were sent for evaluation were, in decreasing order: 956(60.8%), B-cell precursor acute lymphoblastic leukemia (BCP ALL) samples 238(15.1%) T-cell acute lymphoblastic leukemia (T-ALL) samples, 168(10.6%) AML samples, 120 (7.6%) B and T NHL, 42 (2.6%) mixed lineage acute leukemia (MPAL), 34(2.1%) blastic crisis of chronic myeloid leukemia (CML), 14(0.8%) other mature lymphoid neoplasms. Immunophenotyping showed 311(19.78%) positive results for CSF infiltration. The diagnoses of these patients and their respective frequency were: 156 (50.1%) BCP-ALL, 49(15.7%) AML, 41(31.1%) T-ALL, 37(11.8%) NHL, 13 (4.1%) blastic crisis of CML, 8 (2.5%) MPAL, 7(2.2%) other mature lymphoid neoplasms. The frequencies of NHL subtypes observed in this cohort were: 16 (1%) Large B Cell Lymphoma, 7(0.44%) Burkitt Lymphoma, 6 (0.39%) Mantle Cell Lymphoma, 5(0.31%) Adult T-Cell Leukemia-Lymphoma, 1 (0.06%) Marginal Zone Lymphoma, 1 (0.06%) Folicular Lymphoma and 1 (0.06%) Sezary Syndrome. It should be emphasized that among the samples from patients with other mature lymphoid neoplasms, 4 (0.25%) were from patients with Chronic Lymphocytic Leukemia (CLL), which is an unusual finding.

this study observed that 91% of the samples with CSF infiltration were from patients diagnosed with acute leukemia and blastic crisis of CML. Mature lymphoid neoplasms have a lower frequency of CNS infiltration than acute leukemia, as also reflected in our series. These findings show the importance of an accurate assessment of the CSF for these diseases, because the results influence the choice of the therapeutic modality and intensity to be adopted in the different treatment protocols.

we demonstrate the ability of immunophenotyping as a robust method for evaluating CSF samples from patients diagnosed with hematologic malignancies.